Because a synchronous reluctance motor (SynRM) does not require permanent magnets, its industrial applications focus on lowering manufacturing costs. However, the SynRM has disadvantages. It experiences a lower average torque and oscillations derived from torque ripple compared to a permanent magnet-based motor. Therefore, the improvement of torque characteristics is investigated using topology optimization (TO) method which allows a greater variety of rotor structure than the shape optimization technique and does not require the concrete initial structure. Although the level set method is well known among TO methods, the smoothed-heaviside-function-based TO implemented by method of moving asymptotes is more suitable due to the feasibility of implementing the physical structure and the convergence speed. In this paper, the reasonable structure of rotor core in SynRM is investigated using TO method to improve the torque characteristic.

A low-voltage regulator (LVR) is investigated as a countermeasure for voltage violation caused by the integration of photovoltaic (PV) systems in distribution systems. To achieve appropriate voltage control by the LVR, the appropriate control parameters need to be determined. We have proposed schemes to determine the appropriate control parameters using PV forecast profiles. In a previous work, the control parameters were determined on the basis of one-scenario PV forecast, which derives one forecast value in each time step. However, voltage violation could not be avoided by this method in a time step with a large forecast error. In this paper, we propose a method for determining the voltage control parameters of the LVR based on the forecast interval of the PV outputs to quantitatively consider the PV forecast error. The numerical simulation results show that the proposed method can reduce the amount of voltage deviation compared with the conventional method.

We present a novel practical design optimization for the primary core in an induction heating roll, which significantly affects the heating performance. To optimize the 3D eddy current field problem within an acceptable CPU time, we effectively combine 2D magnetostatic optimization and 3D coupled magnetic-thermal FEM. For the 2D optimization, we adopt the level-set method, which has an advantage of being able to derive a feasible shape. However, the disadvantage is that its result occasionally falls into a local optimal solution. To overcome this disadvantage, we propose conducting the initial conceptual design with the linear level-set method before using the nonlinear level-set method to expand the search domain. Furthermore, we incorporate the parallelized move-limit strategy into the level-set method to prevent the configuration from undergoing excess deformation by the operation for the area constraint. Finally, the 2D optimal shape obtained using our new level-set method is converted into a straight line cross-sectional configuration to improve manufacturability, and the final 3D design is created with slits. The final 3D design obtained as a result of the 3D FEM successfully improves both the heating speed and temperature uniformity on the surface of the heating part under the same conditions of input AC current and material volume.

Photovoltaic(PV) power generation systems have gained much attention against a background of energy and environmental problems. However, the output of PV system depends on climate conditions. Therefore, a mass introduction of PV results in the power quality deterioration in the distribution system. To overcome the difficulty, it is effective to introduce Low Voltage Regulator(LVR) to the distribution system. However, the application of LVR brings a new problem, i.e., a control delay for activating the tap after detecting the fluctuation. With this background, to provide more useful predictive information in advance, this paper deals with a novel prediction interval estimation method of 10 second PV fluctuation with two-dimensional kernel density estimation. We also carry out the prediction by using several different methods for comparison, e.g., the conventional method with one-dimensional kernel density estimation and the application of various smoothing methods to this conventional method. Finally, some numerical results, which demonstrate the effectiveness of the proposed method on the basis of several indexes, are also presented.

<p>一般社団法人環境共創イニシアチブが開催する「エネマネハウス2017」に早稲田大学、芝浦工業大学の2大学連合で参加し、本事業を通して改修型ZEHの設計・施工・実証を行った。実証住宅に搭載したヒートポンプ給湯器と蓄電池を日射量の予測値に応じて運用することで、余剰電力をできるだけ自家消費する自立的なエネルギー運用を提案した。本報では、実証住宅の設備・制御計画、日射量予測システム、エネルギー運用の冬季実測結果について述べる。</p>

In a distribution line, power system control and power equipment investment are planned based on a measured power system current. However, recently the mass introduction of photovoltaic (PV) make it difficult for us to precisely measure the demand curve that is a current consumed by electrical equipment because the reversal power flow from PV systems is superposed. Therefore, the prediction of demand curves of distribution line is indispensable for power system management. In addition, it is also necessary to estimate the reliability of the predicted values as well as predicted current itself. In this paper, we propose the estimation method of the prediction interval that is the index of reliability based on the past demand curve database. The feature of the proposed method based on Just-In-Time (JIT) modeling make it possible for us to accurately estimate the prediction interval by the normalized database of demand curve. In this paper, some numerical examples are presented, which demonstrate the effectiveness of the proposed method. (C) 2017 Wiley Periodicals, Inc.

It is very important to design electrical machineries with high efficiency from the point of view of saving energy. Therefore, topology optimization (TO) is occasionally used as a design method for improving the performance of electrical machinery under the reasonable constraints. Because TO can achieve a design with much higher degree of freedom in terms of structure, there is a possibility for deriving the novel structure which would be quite different from the conventional structure. In this paper, topology optimization using sequential linear programming using move limit based on adaptive relaxation is applied to two models. The magnetic shielding, in which there are many local minima, is firstly employed as firstly benchmarking for the performance evaluation among several mathematical programming methods. Secondly, induction heating model is defined in 2-D axisymmetric field. In this model, the magnetic energy stored in the magnetic body is maximized under the constraint on the volume of magnetic body. Furthermore, the influence of the location of the design domain on the solutions is investigated.

Topology optimization is one of the mathematical methods for finding the optimal structure of electrical machinery. Because topology optimization can make a design with much higher degree of freedom in terms of structure than other optimization methods, there is a possibility for achieving a completely new shape that is not limited to the conventional model. The optimized structure is strongly dependent on the characteristic function which is an explicit function with respect to the design variable. To identify the practical topology in which the gray scale elements do not exist as much as possible, Heaviside function is suitable to suppress the generation of gray scale. In this paper, Heaviside function is applied to the IH equipment problem, and both influences of the difference between single and multiple design domain and the difference of the constraint value of the magnetic body volume on optimal solution are particularly investigated.

Topology optimization (TO) has advantages over shape optimization; for example, the design space is wider and the degrees of the shape freedom is larger. The convergence characteristic in the conventional level set (LS) method is slow because of the limitation of the time step size that is used for solving the simplified Hamilton-Jacobi equation, which is normally defined as the width of one finite element in the design domain. To overcome this difficulty, convergence acceleration using the method of moving asymptotes is investigated. The performance of the proposed method is compared with the conventional LS method for a 3-D TO problem regarding the magnetic shielding and an interior permanent magnet motor in a 3-D nonlinear magnetostatic field.

This paper proposes a voltage control method during service restoration in the distribution networks with photovoltaic (PV) generator systems. In the current distribution automation system (DAS) process in Japan, voltage dips and surges occur during service restoration because PVs are disconnected simultaneously after a fault and subsequently reconnected after service restoration. However, in the current DAS, voltage regulators such as an on-load tap changer (OLTC) and step voltage regulators (SVRs) are not controlled during service restoration. The proposed DAS estimates the voltage in a distribution network during service restoration, and it controls the tap position of OLTC and/or SVRs according to the predicted voltage. The numerical simulation results using a real-world distribution system model on a real map and PV output profiles derived by actual square kilometer solar radiation data will be shown. Those results indicate that the proposed DAS prevents voltage deviation that occurs as long as the current DAS is used. The results also show high spatial resolution PV output data are needed to prevent voltage deviation absolutely. (C) 2016 American Society of Civil Engineers.

Topology optimization (TO) is an attractive design tools for electrical machinery. In particular, the level-set-based TO has been investigated enthusiastically. In this paper, a level-set-based topology optimization method supported by the method of moving asymptotes is proposed to realize fast convergence. The performance of the proposed method is verified in comparison with the conventional level-set-based method, which is composed of both gradient-based-correction and regularization.

It is difficult to analyze magnetostatic field problems with multiply connected domains by the direct boundary element method (BEM). On the other hand, there are two methods which can solve magnetostatic field problems with multiply connected domains in double layer charge (DLC) formulation. One uses imaginary loop current to calculate exciting scalar potentials and the other uses the direct BEM to calculate exciting scalar potentials. Thus, in this study, we expand the application scope of the above methods to the direct BEM. The direct BEM is widely used with other analysis methods such as the finite element method (FEM). In that respect, it is also effective to be able to analyze magnetostatic field problems with multiply connected domains by the direct BEM. In addition, results comparing the two methods to analyze multiply connected problems in both the DLC formulation and the direct BEM have not been reported. Therefore, we compare those and systematically clarify their characteristics by calculating a toroidal core model.

&lt;p&gt;It is difficult to analyze magnetostatic field problems with multiply connected domains by the direct boundary element method (BEM). On the other hand, there are two methods which can solve magnetostatic field problems with multiply connected domains in double layer charge (DLC) formulation. One uses imaginary loop current to calculate exciting scalar potentials and the other uses the direct BEM to calculate exciting scalar potentials. Thus, in this study, we expand the application scope of the above methods to the direct BEM. The direct BEM is widely used with other analysis methods such as the finite element method (FEM). In that respect, it is also effective to be able to analyze magnetostatic field problems with multiply connected domains by the direct BEM. In addition, results comparing the two methods to analyze multiply connected problems in both the DLC formulation and the direct BEM have not been reported. Therefore, we compare those and systematically clarify their characteristics by calculating a toroidal core model.&lt;/p&gt;

Photovoltaic (PV) systems have recently attracted considerable attention in the context of environmental problems, antinuclear power movements, and energy problems. Therefore, the large-scale introduction of PV systems is expected in the near future. But the connection of many PV systems to the power system leads to problems. For example, the system voltage often drifts from the norm when reverse power flows increase. Accordingly, optimal system operation is required in order to make maximum use of solar energy to the maximum by installing energy buffers such as storage batteries. In particular, in forecast information, knowledge of the reliability as well as the predicted solar irradiance is essential for effective operation. In this paper, we propose a way of estimating the prediction interval of solar irradiance as an index of reliability by using just-in-time modeling. We consider the accuracy of the prediction interval under many conditions and derive a high-precision estimation method. In addition, we also discuss about the future subjects of study. (C) 2016 Wiley Periodicals, Inc. Published online in Wiley Online Library (wileyonlinelibrary.com).

This paper proposes a novel accuracy improvement technique for the double-layer charge (DLC) formulation in shielding problems. Although the DLC formulation has advantages over the direct methods from the viewpoint of computational cost, the calculation accuracy can be worse because of cancellation errors. In order to improve the accuracy, we apply a new technique based on the difference field concept. Numerical results, which verify the effectiveness of the proposed method, are presented.

Topology optimization (TO) is an effective method for producing practical design of electrical machines. TO is conventionally implemented based on the material density; however, this approach can yield a large number of grayscale areas and unfeasible shapes. On the other hand, when the level-set function is applied to the TO of the magnetic field problem, the potential for obtaining a feasible solution improves. This paper implemented a TO method that uses the regularized level-set function to solve the 3-D nonlinear magnetic field problem. Furthermore, a spatial symmetry condition (SSC), which can introduce the mirror and periodic symmetry of the level-set function from the viewpoint of the electromagnetism, is proposed. To achieve symmetry in the electromagnetic field distribution, the validity of the SSC is investigated and confirmed in a 3-D magnetic shielding problem.

In the case of a mass introduction of PV the instability of PV system output leads to a deterioration of power quality in the distribution system. In this research, we focus on the storage battery operation to achieve a balance between power supply and demand, and perform multi-objective optimization. Specifically, we determine the optimal relationship between the storage battery's charging and discharging rates and the required time resolution for ideal optimization results.

The Output of photovoltaic (PV) systems depends on weather conditions. Therefore if there is a large introduction of PV systems, the power quality in the distribution system will be affected. One effective solution for this problem is to predict PV output. Although the need for prediction information for short period fluctuation is increasing, it is difficult to directly predict a steep fluctuation on the second time scale. For the prediction information of PV output, we propose the estimation of the prediction interval of the fluctuation widths on a 10 second scale. In this paper, we carry out the prediction by using the conventional method, with one-dimensional kernel density estimation, and the proposed method, with two-dimensional kernel density estimation. Then, we discuss the effectiveness of the proposed method based on several numerical indexes.

© 2016 University of Ljubljana. The degree of operational freedom of home appliances is increasing with introducing controllable demand-side appliances by using Home Energy Management System with some communication standard. This situation increases the demands on methodology achieving customer utility maximization, which is able to plan operational strategies of a variety of appliances under various exogenous variables such as energy demand, outlet temperature, and power output of Photovoltaic power generator. Energy demand and photovoltaic output have some uncertainty or variation in the parameter. The objective of this study is to analyze a solution behavior of an operational planning problem adapting Mixed Integer Second-Order Cone Programming extended from traditional Mixed Integer Linear Programming model. The objective function of the mathematical optimization involves mean and its variance by extracting naturally Markowitz model. Above proposed model is intended to sophisticate robust operational planning method, and is also evaluated on the EMS simulation platform that we are developing. As a result, it is found that involving variance to objective function affects to computational time meaning computational load rather than robustness of planned schedule. Additionally, using several scenario results in more robust schedule than using plausible one scenario.

This paper deals with the multi-objective design optimization of the primary core in induction heating roll in consideration of heating performance, cost, and manufacturability. We effectively carry out the shape optimization of the core by combining the 2D level-set method with the 3D finite element method for the coupled nonlinear magnetic-thermal analysis.

The axle counter which detects the position of the train is important railway signal device. This paper deals with a multi-objective optimization of the axle counter by 3D magnetic field analysis. In the optimization, we newly propose the introduction of the conductor plate and carry out its design optimization. It is revealed that the shape optimization of conductor plate enables us to well improve the detection performance of the axle counter from the multi-objective point of view.

In this paper, we propose a novel analysis method with local expantion edge elements, in which the interpolation of the potential in the radial direction is defined besed on the idea of the local expansion. It enables us to accurately analyze the physical quantity in the targeted finite region as more smoothed values.

&lt;p&gt;In a distribution line, power system control and power equipment investment are planned based on a measured power system current. However, recently the mass introduction of PV make it difficult for us to precisely measure the demand curve that is a current consumed by electrical equipment because the reversal power flow from PV systems is superposed. Therefore, the prediction of demand curves of distribution line is indispensable for power system management. Additionally, it is also necessary to estimate the reliability of the predicted values as well as predicted current itself. In this paper, we propose the estimation method of the prediction interval that is the index of reliability based on the past demand curve database. The feature of the proposed method based on Just-In-Time (JIT) modeling make it possible for us to accurately estimate the prediction interval by the normalized database of demand curve. In this paper, some numerical examples are presented, which demonstrate the effectiveness of the proposed method.&lt;/p&gt;

The Output of photovoltaic (PV) systems depends on weather conditions. Therefore if there is a large introduction of PV systems, the power quality in the distribution system will be affected. One effective solution for this problem is to predict PV output. Although the need for prediction information for short period fluctuation is increasing, it is difficult to directly predict a steep fluctuation on the second time scale. For the prediction information of PV output, we propose the estimation of the prediction interval of the fluctuation widths on a 10 second scale. In this paper, we carry out the prediction by using the conventional method, with one-dimensional kernel density estimation, and the proposed method, with two-dimensional kernel density estimation. Then, we discuss the effectiveness of the proposed method based on several numerical indexes.

In the case of a mass introduction of PV the instability of PV system output leads to a deterioration of power quality in the distribution system. In this research, we focus on the storage battery operation to achieve a balance between power supply and demand, and perform multi-objective optimization. Specifically, we determine the optimal relationship between the storage battery's charging and discharging rates and the required time resolution for ideal optimization results.

This paper proposes a new pulse width modulation (PWM) carrier distribution technique for reducing motor electromagnetic noise. The proposed method uses only two carrier frequencies and controls PWM harmonics by the transferring probability of the two carrier frequencies. The proposed method is verified by experiments using 0.8kW PMSM.

In this paper, a magnetic-polarity detection method for a permanent-magnet reluctance motor (PRM) is presented. The inductance characteristics of a PRM are different from those of common interior permanent-magnet synchronous motors and are verified by an electromagnetic field analysis. Moreover, a novel magnetic-pole detection method is proposed using the inductance characteristics of a PRM. The proposed method is verified by experiments using a 90-kW PMSM.

Electromagnetic phenomena intrinsically spread over an infinite region. Thus, efficient handling of open boundaries is one of the main issues in electromagnetic field computations. This paper deals with the orthogonalized infinite edge element method that efficiently performs precise analysis of the infinite region. In this method, several parameters are used to achieve high accuracy. As one of the parameters, we focus on the reference point and investigate the effect of its position setting on accuracy. We also evaluate the accuracy of the calculated magnetic field in the far region. By applying boundary element method as postprocessing, it is found that high computational accuracy in the region can be effectively achieved.

The infinite edge element method (IEEM) has been proposed as an effective method for efficiently handling open boundary region, i.e., the air region. In this paper, we present a newly defined infinite element radiated from a reference plane (RPL), and propose the combination method using various infinite element configurations, such as radiated configurations from a reference point, a reference line, and an RPL. By using the proposed hybrid method, we can drastically decrease the number of ill-shaped infinite elements and improve the computational accuracy and convergence characteristics in comparison with the conventional IEEM, especially in the case of flattened analysis models.

The axle counter as a train detector is one of the important railway signaling devices for accurate and safe train control systems. This paper deals with a design optimization of the axle counter by large-scale magnetic field computations. To efficiently reduce the computational burden in the optimization, we accurately estimate the signaling level by applying infinite edge elements to an extensive air domain, which results in a practical design approach within an acceptable CPU-time.

PV system recently attracts much attention on the back of environmental problems, antinuclear power movements and energy problems. Therefore, a large scale introduction of PV system is expected in the near future. On the other hand, a lot of PV systems connected to the power system bring on some problems. For example, a system voltage often drifts from the norm when the reverse power flow increase. Accordingly, it is necessary to perform an optimal system operation in order to utilize a solar energy to the maximum by installing energy buffers, e.g. storage batteries. Especially, the forecast information i.e., the reliability as well as predicted solar irradiance is essential for the effective operation. In this paper, we propose a way to estimate the prediction interval of the solar irradiance as an index of reliability by using Just-In-Time Modeling (JIT Modeling). We consider the accuracy of the prediction interval under many conditions and derive the high-precision estimation method. In addition, we also talk about the future outlook of this study.

The nonlinear magnetic properties of an iron core should be considered when topology optimization (TO) is applied to a realistic problem. However, a scheme for introduction of the magnetic nonlinearity to material-density-based TO has not been rigorously established. In this paper, TO by using material density with magnetic nonlinearity is proposed. The numerical instability of the sequential linear programming method is a well-known topic. The stabilized sequential linear programming method, which realizes the stabilized convergence characteristics of an objective function, is proposed and investigated in the 3-D design problem of a magnetic circuit.

In the past, we have proposed battery operations in a photovoltaic (PV) system using PV output and load power forecasts. In the proposed method, we utilized multiobjective optimization for a residential area model that includes a large number of PV systems with storage batteries. To practically demonstrate that the proposed operation effectively improves economic and environmental efficiency, it is indispensable to evaluate the effects of forecast error on the operation design of a PV system with storage battery. In this paper, we propose a method for evaluating the robustness of battery operation taking account of the statistical characteristics of forecast errors. Some numerical examples, which show the validity of the proposed method, are also presented.

Residential houses are in the process of introducing power generators such as photovoltaic (PV) power generators and fuel cell cogeneration systems. Under current laws in Japan, surplus electricity from a residential PV system can be sold by feeding it back into the electrical grid. However, when a lot of neighboring power generators make and feed back electricity at the same time, there is an issue of an upper voltage violation of the provisions of the laws and regulations relating to the Electricity Business Act in the distribution system of the electrical grid. The issue has been solved by stopping power generators when they reach an upper voltage limit, 107V. Another solution is to acknowledge demand response signal from electrical grid operator to store electricity in residential batteries using Home Energy Management System (HEMS). The research question is that how to collaborate HEMS and Grid Energy Management System (GEMS). This paper developed an evaluation framework for the cooperative behavior between HEMS and GEMS. Using this evaluation framework, this paper demonstrated the optimal operational strategy of HEMS including PV in the case that HEMS is informed voltage profile from GEMS, and also assessed amount of PV suppression quantitatively in residential sector in practical aspect.

Demand-side electricity saving is an important factor in the reduction of the installed capacity of power-supply facilities. In order to save electricity automatically while maintaining comfort levels, home energy management systems (HEMS) have attracted attention. These systems can control residential energy equipment cooperatively to reduce electricity consumption while considering benefits to consumers. Although many researchers have evaluated HEMS, no one has conducted a study which considers the control of various types of residential energy equipment in real time along with the uncertainties of energy demands. This paper proposes a single HEMS method which connects prediction, operational planning and control steps and enables the evaluation of operational planning methods of HEMS connected with many kinds of residential energy equipment currently in use in Japan while considering the uncertainties. The purpose of this study is to evaluate the economic potential of residential energy systems based on the proposed method with the uncertainties of energy demands and photovoltaic (PV) output under time-of-use prices. The results allowed us to establish a framework to quantitatively evaluate the operational planning methods of HEMS with the uncertainties of energy demands and PV output. In addition, the usability of the proposed method was confirmed by comparing the operational costs to those of a reference method.

Residential houses are in the process of introducing power generators such as photovoltaic (PV) power generators and fuel cell cogeneration systems. Under current laws in Japan, surplus electricity from a residential PV system can be sold by feeding it back into the electrical grid. However, when a lot of neighboring power generators make and feed back electricity at the same time, there is an issue of an upper voltage violation of the provisions of the laws and regulations relating to the Electricity Business Act in the distribution system of the electrical grid. The issue has been solved by stopping power generators when they reach an upper voltage limit, 107V. Another solution is to acknowledge demand response signal from electrical grid operator to store electricity in residential batteries using Home Energy Management System (HEMS). The research question is that how to collaborate HEMS and Grid Energy Management System (GEMS). This paper developed an evaluation framework for the cooperative behavior between HEMS and GEMS. Using this evaluation framework, this paper demonstrated the optimal operational strategy of HEMS including PV in the case that HEMS is informed voltage profile from GEMS, and also assessed amount of PV suppression quantitatively in residential sector in practical aspect.

This paper studies a magnetic polarity detection method for permanent magnet reluctance motor (PRM). Inductance characteristic of PRM is different from that of common interior permanent magnet synchronous motor. The inductance characteristic of PRM is verified by electromagnetic field analysis. Moreover, this paper proposes novel magnetic polarity detection method using the inductance characteristic of PRM. The proposed method is verified by experiments using a 90-kW PRM.

Recently, for the purpose of utilizing renewable energy in a community, interactive electricity power networks, such as smart grid, have received much attention. In those electricity power networks, the technologies for maintain the balance of electricity demand and supply in a limited area become more important. Installing photovoltaic system can be effective for supplying electricity in a limited area at the peak load time, but PV output depends on weather conditions. Thus we propose to combine PV power generation with demand response program. We simulate interchange PV power with demand response program in a residential community. Some numerical results, which demonstrate the validity of the proposed method, will be presented.

Output of the photovoltaic (PV) system drastically fluctuates depending on weather conditions. Therefore users of PV systems should manage their energy usage with forecast information of the PV output. Due to the reasons above, we have developed an estimation method of X% prediction interval of solar irradiance. We have achieved a high-accuracy prediction interval for any prediction coefficient X%. However, we found that there are some errors in a case where the prediction coefficient is high. In this paper, we improve the estimation algorithm of the prediction interval.

This paper presents a distribution automation system (DAS) for service restoration in the distribution network with photovoltaic (PV) generator systems, which are disconnected simultaneously after a fault and subsequently reconnected after service restoration. Because the reverse power flow of PVs affects voltage in the distribution system, voltage dips and surges occur during the service restoration. However, current DAS do not control voltage regulators such as an on-load tap changer (OLTC) and step voltage regulators (SVRs) during the service restoration. The proposed DAS estimates the voltage in a distribution network considering the simultaneous disconnection of PVs by performing power flow calculations, and it controls the tap position of OLTC and/or SVRs according to the predicted voltage deviation. The voltage after the disconnection of PVs is calculated by estimating the PV output utilizing square kilometer solar radiation data calculated using satellite image data in real time.

When using the indirect method in magnetostatic analysis, the magnetic material is represented by the double-layer charge on the material surface. The double-layer charge offers an integral form of scalar potential to give a boundary integral equation (BIE). A unified integral form of excitation potential has been derived, resulting in a BIE capable of solving generic problems. When we apply the standard BIE to analyze magnetic shields by thin shells with high permeability, we usually cannot get accurate results in the shielded space. To accurately solve shielding problems using rough meshes, in this paper we propose a new modeling approach by using a concept of the boundary element method.

This paper derives an effective shape of the flux barrier in an interior permanent magnet (IPM) motor. IPM motors generally have many design parameters such as the current phase angle, shape of the rotor and stator's iron core, and shape and position of the magnet. The flux barrier plays an important role in controlling torque characteristics. We apply topology optimization (TO) to the rotor core using a multistep genetic algorithm to determine an effective flux barrier. Furthermore, we extend the TO to combinatorial optimization for considering its effect on the current phase angle. Thus, a reasonable flux barrier with an optimal phase angle is determined.

Topology optimization (TO) makes it possible to obtain new structures for electrical machines. The sensitivity-based method, which can cope with some constraint conditions, is suitable for large-scale three-dimensional TO. However, if the material density is defined by unknown variables in TO, elements with intermediate density (grayscale) occasionally appear. The grayscale cannot clearly show the material allocation within its finite element. Thus, we propose a sigmoid-based filtering function to suppress the generation of grayscale. Moreover, because the constraint condition can be simply taken into consideration, sequential linear programming is occasionally utilized as a topology optimizer. However, the convergence characteristics frequently oscillate and are strongly dependent on the move limit that controls the maximum intensity of the correction vector. To overcome this numerical difficulty, we propose an identification technique for the determination of a quasi-optimal move limit (QOML). This paper demonstrates the performance of both the mathematical function filtering grayscale and QOML.

This paper deals with a large-scale eddy-current analysis of the constructions in railway system from the view point of electromagnetic noise assessment. To reduce computational costs with the calculation accuracy kept, we develop some numerical methods and demonstrate their effectiveness using a practical large-scale model.

This study derives a high performance flux barrier for an interior permanent magnet (IPM) motor using binary-based topology optimization (TO). TO has a higher degree of optimization than size or shape optimization. An IPM motor has many design parameters including the current phase angle, core shape of rotor and stator, and magnet position and shape. The flux barrier in an IPM motor plays a particularly important role, influencing several characteristics. We apply TO, using a multistep genetic algorithm, to the rotor core in order to determine a flux barrier with the highest torque performance.

Purpose - The purpose of this paper is to improve the multistep algorithm using evolutionary algorithm (EA) for the topology optimization of magnetostatic shielding, and the paper reveals the effectiveness of methodology by comparison with conventional optimization method. Furthermore, the design target is to obtain the novel shape of magnetostatic shielding.
Design/methodology/approach - The EAs based on random search allow engineers to define general-purpose objects with various constraint conditions; however, many iterations are required in the FEA for the evaluation of the objective function, and it is difficult to realize a practical solution without island and void distribution. Then, the authors proposed the multistep algorithm with design space restriction, and improved the multistep algorithm in order to get better solution than the previous one.
Findings - The variant model of optimized topology derived from improved multistep algorithm is defined to clarify the effectiveness of the optimized topology. The upper curvature of the inner shielding contributed to the reduction of magnetic flux density in the target domain.
Research limitations/implications - Because the converged topology has many pixel element unevenness, the special smoother to remove the unevenness will play an important role for the realization of practical magnetostatic shielding.
Practical implications - The optimized topology will give us useful detailed structure of magnetostatic shielding.
Originality/value - First, while the conventional algorithm could not find the reasonable shape, the improved multistep optimization can capture the reasonable shape. Second, An additional search is attached to the multistep optimization procedure. It is shown that the performance of improved multistep algorithm is better than that of conventional algorithm.

The topology optimizations which optimize a material arrangement on an element, without extracting feature quantity, are attractive methods, because we can obtain a free idea of the initial design of magnetic devices. However, in actual design processes, all of the required features of the products cannot be included objective functions, such as ease of manufacture or influence of rise in heat. Moreover, the multiple-purpose optimizations concerning many kinds of physical phenomena have difficulty with calculation time. Thus, it is necessary to estimate whether the obtained optimal solution under the limited condition is applicable to an actual designing of magnetic devices. This paper introduces two-step topology optimization method using the constraints on the similarity of the topology, which provides us various topologies including suboptimal solutions. By using the proposed method, we can determine some actual applicable solutions out of obtained solutions. The proposed method was verified by applying it to the C-core problem and the magnetic shield problem, which demonstrated the effectiveness of the proposed method.

Against a background of environmental problems and energy issues, it is expected that PV systems will be introduced rapidly and connected with power grids on a large scale in the future. For this reason, concerns about how PV power generation will affect supply and demand adjustment in electric power in the future arise, and the technique of correctly grasping PV power generation becomes increasingly important. PV power generation depends on solar irradiance, module temperature, and solar spectral irradiance. Solar spectral irradiance is the distribution of the light intensity for every wavelength. As the spectral sensitivity of solar cells depends on the kind of solar cell, it becomes important for an exact grasp of PV power generation. But the preparation of solar spectral irradiance data is not easy because observational instruments for solar spectral irradiance are expensive. Against this background, in this paper, we propose a new method based on statistical pattern recognition for estimating the spectrum center, which is a representative index of solar spectral irradiance. Some numerical examples obtained by the proposed method are also presented. (c) 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 184(1): 1018, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22393

The electromagnetic phenomena intrinsically spread over the infinite space. Thus, the efficient handling of the open boundary is one of the main issues in the electromagnetic field computation. This paper proposes the infinite edge element method (IEEM) with the boundary surface integration to accurately obtain the magnetic field, i.e., the derivatives of vector potentials, in the far-field region.

PV power output mainly depends on solar irradiance, which is affected by various meteorological factors. Thus, it is required to predict solar irradiance in the future for the efficient operation of PV systems. In this paper we develop a novel approach for solar irradiance forecasting, in which we combine the black-box model (JIT modeling) with the physical model (GPV data). We investigate the predictive accuracy of solar irradiance over a wide controlled area of each electric power company by utilizing measured data from 44 observation points throughout Japan provided by JMA and 64 points around Kanto provided by NEDO. Finally, we propose an applied forecasting method of solar irradiance to deal with difficulties in compiling databases. We also consider the influence of different GPV default times on solar irradiance prediction. (C) 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 182(4): 19-28, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22338

Analysis and modeling of electric energy demand is indispensable for power planning, operation, facility investment, and urban planning. Because of recent development of renewable energy generation systems oriented for households, there is also a great demand for analysing the electricity usage and optimizing the way to install electricity generation systems for each household. In this study, employing statistical techniques, a method to model daily consumption patterns in households and a method to extract a small number of their typical patterns are presented. The electricity consumption patterns in a household is modeled by a mixture of Gaussian distributions. Then, using the symmetrized generalized Kullback-Leibler divergence as a distance measure of the distributions, typical patterns of the consumption are extracted by means of hierarchical clustering. The statistical modeling of daily consumption patterns allows us to capture essential similarities of the patterns. By experiments using a large-scale dataset including about 500 houses' consumption records in a suburban area in Japan, it is shown that the proposed method is able to extract typical consumption patterns. © 2010-2012 IEEE.

The electromagnetic phenomena intrinsically spread over the infinite region. Thus, the efficient handling of open boundary is one of the main issues in the electromagnetic field computations. This paper deals with the orthogonalized infinite edge element method which efficiently performs precise analysis of the infinite region. In this method, there are several parameters to achieve its high accuracy. As one of the parameters, we focus on the reference point and investigate the effect of its position setting on the accuracy. Furthermore, we also evaluate the accuracy of the calculated magnetic field at distance region. By applying boundary element method (BEM) as post-processing, it is found that the high computational accuracy in the region can be effectively achieved. © 2013 The Institute of Electrical Engineers of Japan.

Topology optimization using the binary information of magnetic material is one of the most attractive simulations for the conceptual design of electrical machines. Heuristic algorithms based on random search allow engineers to define general-purpose objects with various constraint conditions. However, it is difficult for topology optimization to realize a practical solution without island and void distribution. In this paper, we propose a hybrid evolutionary algorithm that is composed of a genetic algorithm (GA) and extended compact GA (ECGA). We verify the effectiveness of the proposed algorithm on the binary topology optimization problem for the design of magnetostatic shielding. © 1965-2012 IEEE.

This paper investigates the effectiveness of the time domain parallelization in magnetic field analyses of practical electric machines. We propose an efficient procedure to parallelize transient as well as steady-state analyses by generalizing the formulation of the parallel time-periodic finite element method. The proposed method is called the time domain parallel finite element method (TDPFEM) because it can be applied to both transient and steady-state analyses. Additionally, we derive a special condition of the slip to reduce computational costs for steady-state analyses of induction motors by using a half-cycle polyphase time-periodic condition. © 1965-2012 IEEE.

Since the line loop current is equivalent to the double layer charge, it gives an integral form of scalar potential. The segmental loop current on the interface between magnetic materials produces a potential gap, which works to give a boundary integral equation (BIE). By virtue of another potential gap due to a fictitious circulating current along the contour of cut-surface in the material, the excitation potential becomes single valued and the BIE becomes applicable to generic problems without any restriction. Regarding the nonlinear magnetic material as composed of segmental materials with different values of permeability, we get the same BIE for the nonlinear analysis as for the linear analysis. In order to check the adequacy and effectiveness of the nonlinear BIE, we solve a typical magnetostatic problem and compare the computed results with those by the conventional magnetic moment method. © 1965-2012 IEEE.

In the past, we have proposed some battery operations in a photovoltaic (PV) system using the PV output and load power forecasts. In the proposed method, we utilized multi-objective optimization for a residential area model that includes a large number of PV systems with storage batteries. To practically demonstrate that the proposed operation effectively improves the economic and environmental efficiencies, it is indispensable to evaluate the forecast error effects on operation design of PV system with storage battery. In this paper, we propose a method for evaluating the robustness of battery operation taking account of the statistical characteristics of forecast errors. Some numerical examples, which show the validity of the proposed method, are also presented. © 2013 The Institute of Electrical Engineers of Japan.

In this study, we examine the relationship between harmonic voltage injection, acoustic noise, and position estimation performance in a PMSM when a position-sensorless control method involving harmonic voltage injection is used at low speeds. Further, we propose a novel control method for voltage injection; this method can be used to reduce acoustic noise in the motor. The proposed control method is verified by performing numerical simulations and carrying out experiments using a four-pole, 2-kW, 2100-rpm IPMSM (interior permanent-magnet synchronous motor). (c) 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(3): 4956, 2012; Published online in Wiley Online Library (). DOI 10.1002/eej.21246

This paper investigates the effectiveness of various methods to accelerate the convergence to a steady state in time-periodic electromagnetic field problems. We first introduce the time-periodic explicit error correction (TP-EEC) method taking account of both the dc and linearly-varying error components and propose the harmonics TP-EEC method which enables us to achieve the increase in error correction frequency. Then, we discuss the convergence property of the TP-EEC methods based on the error analysis. The advantages and disadvantages of the TP-EEC method and the time differential correction (TDC) method are investigated from the viewpoints of computational costs and application scope.

Adopting the integral representation of scalar potential due to double layer charge, we derive a boundary integral equation with one unknown to solve magnetostatic problems. The double layer charge produces a potential gap at the air-material boundary without disturbing the continuity of normal magnetic flux density and the potential gap makes the tangential component of magnetic field continuous; accordingly, the boundary conditions are fully fulfilled even with one unknown. The boundary integral equation is capable of solving the double layer charge at edges and corners. Once the double layer charge is solved, it gives directly the magnetic flux density by Biot-Savart law. In this paper, we investigate how to evaluate the magnetic flux density at the vertex.

The scalar potential formulation by the boundary integral equation approach is attractive for numerical analysis but has fatal drawbacks due to a multi-valued function in current excitation. We derive an all-purpose boundary integral equation with double layer charges as the state variable and apply it to nonlinear magnetostatic problems by regarding the nonlinear magnetization as fictitious volume charges. We investigate two approaches how to treat the fictitious charges. In discretization by the constant volume element, a surface loop current is introduced for the volume charge. By the linear volume element, the fictitious charges are evaluated on the condition that the divergence of the magnetic flux density is zero. We give a comparative study of these two approaches.

This paper investigates the parallelization of the time-periodic finite-element method in nonlinear magnetic field analyses of rotating machines. The developed method, which can obtain the steady state solutions directly, provides large granularity even in the small-scale problems compared with the ordinary parallel FEM based on the domain decomposition approach. Furthermore, we apply the parallel TPFEM to analyses of induction motors which have different time periodicities in stator and rotor regions due to the slip. Numerical results verify the effectiveness of the developed method.

This paper proposes an orthogonalization of the Hilbert matrix in element matrices of the infinite edge elements. The validity of the infinite edge element is demonstrated in previous researches, but the Hilbert matrix results in extremely slow convergence in the ICCG method, especially when using higher order expansions. The proposed orthogonalization technique improves the convergence drastically and it makes the infinite elements practical in the electromagnetic FEM analysis of the open boundary problems in quasi-static magnetic fields.

With a background of environmental problems and energy issues, it is expected that PV systems will be introduced rapidly and connected with power grids on a large scale in the future. For this reason, the concern to which PV power generation will affect supply and demand adjustment in electric power in the future arises and the technique of correctly grasping the PV power generation becomes increasingly important. The PV power generation depends on solar irradiance, temperature of a module and solar spectral irradiance. Solar spectral irradiance is distribution of the strength of the light for every wavelength. As the spectrum sensitivity of solar cell depends on kind of solar cell, it becomes important for exact grasp of PV power generation. Especially the preparation of solar spectral irradiance is, however, not easy because the observational instrument of solar spectral irradiance is expensive. With this background, in this paper, we propose a new method based on statistical pattern recognition for estimating the spectrum center which is representative index of solar spectral irradiance. Some numerical examples obtained by the proposed method are also presented. © 2012 The Institute of Electrical Engineers of Japan.

The volume integral equation approach replaces magnetic materials with the magnetization in magnetostatic analysis. The concept of magnetic shell relates the magnetization with loop currents. The loop current is equivalent to the magnetic double layer, which gives an integral form of the scalar potential. The nonlinear magnetic field is formulated by regarding the nonlinear magnetization as volume magnetic charges. This paper presents how to utilize the volume charge to solve nonlinear problems. In the case of constant volume element we replace the volume charges with the surface loop currents to derive the nonlinear boundary integral equations having the line and surface loop currents as unknowns. The boundary integral equation is solved iteratively while improving alternately the loop and surface currents.

Electricity consumption in households varies dependent on a lot of possible reasons such as lifestyle, family configuration, and weather. It is of great importance to optimize the electricity generation system to install for each household. In our previous work, we proposed a clustering approach for extracting a small number of basic electricity consumption patterns in a household. In this study, we apply the method to a larger dataset with many households. In the previous work, we determined the number of basic patterns in a heuristic manner. In this work, we use gap statistics to automatically determine an appropriate number of basic patterns, and we obtained a reasonable result on a large-scale data.

This paper develops a parallel fast multipole method specialized for uniform brick elements to achieve large-scale micromagnetic simulations of a practical perpendicular recording head within acceptable computation time. In highly parallel computation, it is indispensable to equally distribute the computing load among processes so as to obtain the good parallel speedup. The load balancing technique which can be regarded as the domain decomposition method based on octree structure in the fast multipole method is discussed. The scalability of the parallel fast multipole accelerated micromagnetic simulation is investigated with 100 or more MPI processes.

In this paper, we describe a study of mesh deformation methods for magnetic field analysis. We propose an efficient method that is a combination of two conventional mesh deformation methods. We numerically estimate the basic performance of the proposed method and conventional methods using three-dimensional mesh models for magnetic field analysis. We highlight the advantages of the proposed method with respect to its robustness and computational cost. (C) 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons,

This paper proposes a novel effective method for open boundary problems by using the finite-element method (FEM) with a new formulation of the infinite edge element. We developed the formulation of the infinite element by adopting the characteristic of conventional edge elements, resulting in a sparse and symmetric matrix. This proposed technique with the infinite edge element has the advantage of drastically reducing the computational burden with keeping the analyses' accuracy. Some numerical examples which demonstrate the validity of the proposed method are presented.

This paper develops the time-periodic explicit error correction (TP-EEC) method for the convergence acceleration to a steady state in transient analysis of synchronous machines. The methods to deal with the movement of the rotor and different time-periodicity in the fixed and moving parts of the mesh are investigated. Furthermore, we propose the novel TP-EEC method based on the polyphase time periodic condition. Numerical results verify the effectiveness of the developed methods.

This paper investigates the scalability of a parallel fast multipole accelerated boundary integral equation method in electrostatic field analyses. A load balancing technique suitable for highly parallel computation with 100 or more processes, which is a domain decomposition method based on octree structure in the FMM, is also proposed. Numerical results clarify the effectiveness of the developed method in practical models with complicated geometry.

This paper investigates a large-scale analysis of magnetic particles&apos; behavior in magnetic fields by using a novel method combining the discrete element method and the magnetic interaction calculation with the fast multipole method (FMM). Furthermore, the effective formulae for the derivative of the magnetic field in the FMM procedure, which is necessary to calculate magnetic forces among a large number of magnetic particles, are proposed. Numerical examples of large-scale magnetic-particle chain analysis that demonstrate the effectiveness of the proposed method are presented. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3556914]

In the near future, photovoltaic (PV) power generation systems will become widespread. In this study, we apply multi-objective optimization to the designed model: the concentrated introduction of PV systems with stationary batteries and electric vehicle (EV) batteries in housing areas to fulfill the diverse demands from various sectors, including electrical power companies and utility customers. In the computations, we propose a novel method for modeling the residential load and PV output power based on the measured data from a national research project in Japan. Furthermore, we carry out data mining of the optimization results using a self-organizing map as an effective analysis tool for the design of PV systems with storage batteries.

PV power output mainly depends on the solar irradiance which is affected by various meteorological factors. So, it is required to predict solar irradiance in the future for the efficient operation of PV systems. In this paper, we develop a novel approach for solar irradiance forecast, in which we introduce to combine the black-box model (JIT Modeling) with the physical model (GPV data). We investigate the predictive accuracy of solar irradiance over wide controlledarea of each electric power company by utilizing the measured data on the 44 observation points throughout Japan offered by JMA and the 64 points around Kanto by NEDO. Finally, we propose the application forecast method of solar irradiance to the point which is difficulty in compiling the database. And we consider the influence of different GPV default time on solar irradiance prediction. © 2011 The Institute of Electrical Engineers of Japan.

Recently, remarkable developments of new energy technologies have been achieved against various energy problems. Photovoltaic (PV) system, one of such technologies, has an advantage of utilizing infinite and clean energy. On the contrary, it also has a disadvantage of unreliable power supply mainly caused by unstable weather. The fluctuation of the power supply of PV systems are considerably large because of rapid insulation changes and rapid weather changes, and in some cases, it seems impossible to realize high-accuracy prediction even with sophisticated prediction models. In this paper, using recently proposed estimator for the Shannon information content, a method to output a measure of credibility for prediction is proposed. With the proposed method, it is possible to judge whether the energy supply at a certain future time is unpredictably fluctuate compared to the current value or not, and it is possible to take measures against the rapid change of solar energy generation in advance. From an experimental result using solar energy supply data, we see that the proposed measure of credibility reflects the difficulty of predicting solar energy supply. © 2011 IEEE.

In the near future, it is expected the widespread use of electric vehicles (EVs). And a lot of retail stores will have EV quick chargers. This might cause a problem that is a rise in electricity costs of the stores because of an increase in maximum load power. The stores want to reduce electricity cost especially related with load peak for low cost operation. Installation of photovoltaic (PV) and storage battery system are one of the solutions for peak cutting. So it is important to decide the reasonable system scale to install. On the other hand, the stores also want to make battery lifetime longer for low cost operation. Thus, an optimization method of system installation and operation for a retail store is discussed in this paper. In the first step, the system scale is optimized, whose purpose is maximizing the effect of peak cut with minimum installation cost. In the optimization, a genetic algorithm (GA) is employed to solve the multi-objective trade-off problem. In the next step, system operation is optimized to make battery lifetime longer. In order to extend the battery lifetime, start timing control of the EV quick charge is effective. However, start timing control delays the beginning of charging, which makes it unattractive for customers. The relationship between delay time and battery lifetime improvement is investigated. And a design method to achieve long system lifetime is shown. © 2011 IEEE.

Recently, many people in the world pay attention to the renewable energy and a photovoltaic system becomes especially worthy for the future of the earth. In this paper, we investigate the operation of PV system with storage battery by using next-day residential load forecast. First, we propose the application of a simple and high-precision modeling method, i.e., Just-In-Time Modeling to the forecast of residential load. And we carry out the improvement in predictive accuracy by the input selection and the weighting method. Next, we simulate the operation of PV system with storage battery by using the load forecast information. The result shows that the introduction of load forecast into PV system operation contributes to environmental conservation and reduction of operating cost. © 2011 IEEE.

Recently, photovoltaic (PV) system has attracted attention because of serious environmental and energy problems. However, if PV systems are intensively connected to the grid in a specific area, it is predicted that the voltage of the distribution feeder in power system increases due to the reversal power flow. Such degradation of electric power quality leads to the depression of PV output by power conditioners. In our previous research, we have overcome the problem by introducing the storage batteries and optimally charging and discharging them [1][2]. On the other hand, the residential fuel cell (FC) system has been a focus of attention because FC has achieved a primary energy efficiency of 80% by making the best use of generator waste heat. When the FC system is operated according to the residential thermal demand as a general operation, its electric output doesn't always follow the residential electric load. Therefore, it is also indispensable to introduce the storage battery to the hybrid system with a combination of PV subject to weather condition and FC giving the priority to heat supply. In this paper, we investigate the optimal operation of the storage battery for the hybrid PV and FC system. © 2011 IEEE.

Solar power, wind power, and co-generation (combined heat and power) systems are possible candidate for household power generation. These systems have their advantages and disadvantages. To propose the optimal combination of the power generation systems, the extraction of basic patterns of energy consumption of the house is required. In this study, energy consumption patterns are modeled by mixtures of Gaussian distributions. Then, using the symmetrized Kullback-Leibler divergence as a distance measure of the distributions, the basic pattern of energy consumption is extracted by means of hierarchical clustering. By an experiment using the Annex 42 dataset, it is shown that the proposed method is able to extract typical energy consumption patterns. © 2011 IEEE.

This paper proposes a novel method for the improvement of the convergence to a steady state in time-periodic transient nonlinear eddy-current analyses. The proposed method, which is based on the time-periodic finite element method and the singularity decomposition-explicit error correction method, can extract poorly converged error components corresponding to the large time constants of an analyzed system. The correction of the extracted error components efficiently accelerates the convergence to a steady state. Numerical results verify the effectiveness of the proposed method.

This paper investigates a mutually reverse (MR) unit coil as a wheel detector, which is more insusceptible to electromagnetic noise than conventional wheel detectors. We carry out the optimal design of the receiving coils for the further accurate detection of the wheel by means of magnetic field computations. Then, we accurately estimate the signaling receive level in spite of efficiently reducing the computational burden by the response surface methodology. Furthermore, we propose the robust design of the receiving coils by considering the degradation of the signaling receive level due to the positioning error.

This paper describes a benchmark model proposed for the clarification of the characteristic of various methods for modeling the laminated iron core. In order to obtain a reference solution of the benchmark model, a large-scale nonlinear magnetostatic field analysis with a mesh fine enough to represent the microscopic structure of the laminated iron core is carried out by using the hybrid finite element-boundary element (FE-BE) method combined with the fast multipole method (FMM) based on diagonal forms for translation operators. The computational costs and accuracy of two kinds of homogenization methods are discussed, comparing them with the reference solution. As a consequence, it is verified that the homogenization methods can analyze magnetic fields in laminated iron core within acceptable computational costs. (C) 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(1): 26-35, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20809

Recently, a photovoltaic (PV) system has attracted attention because of serious environmental and energy problems. In near future, PV systems intensively connected to the grid will bring about the difficulties in the power system operation. As a countermeasure, this paper deals with the introduction of storage battery for making the unstable PV power controllable. In this regard, when we introduce a storage battery into a PV system, we have to consider the advantages and disadvantages. In order to evaluate the system from various perspectives, we have carried out multi-objective optimization of battery operation in PV system design. However, as the number of objective functions increases, it becomes difficult to appropriately interpret the correlation among objective functions and design variables. With this background, in this paper, a novel computational method is proposed for data mining of PV system design, in which we make an attempt to effectively extract the design information of the battery system with the use of Self-Organizing Map (SOM). © 2010 The Institute of Electrical Engineers of Japan.

Recently, total number of distributed generators (DGs) such as photovoltaic generation system and wind power generation system connected to an actual distribution network increases drastically. The distribution network connected with many distributed generators must be operated keeping reliability of power supply, and power quality. In order to accomplish active distribution network operation to take advantage of many connections of DGs, a new coordinated operation of distribution system with many connections of DGs is necessary. So far, the authors have proposed a coordinated operation of distribution network system connected with many DGs by using sectionalizing switches control method, sending voltage control method, computation method of acceptable maximum output of DG and determination method of optimal smoothing time constant of wind power generation system with storage battery. In this paper, the authors develop an experiment of scaled-down three-phase distribution system with distributed generators in order to check the validity of the proposed approach. © 2010 The Institute of Electrical Engineers of Japan.

This paper investigates the acceleration of convergence to a steady state in a transient analysis of rotating machines using the time-periodic explicit error correction (TP-EEC) method. The efficient method to deal with the movement of the rotor and different time-periodicity in the fixed and moving parts of the mesh is developed. Numerical results verify the effectiveness of the developed method. © 2010 IEEE.

The electromagnetic phenomena intrinsically spread over the infinite space. Thus, the efficient handling of open boundary is one of the main issues in the electromagnetic field computations. This paper deals with a FE formulation combined with infinite elements as a novel effective method for open boundary problems. Some numerical examples which demonstrate the validity of the proposed method are presented. © 2010 IEEE.

In the design optimization of electric machine, there is a strong need to comprehend in detail the tradeoff relationships among the various objective functions. Therefore, it is important to obtain the sufficiently diverse pareto solutions for appropriately designing electric machine. However, the conventional genetic algorithm (GA) doesn't necessarily find out the diverse pareto solutions. In this paper, we propose a GA with new concept of crowding distance which enables us to obtain the sufficiently diverse pareto solution. Some numerical examples which demonstrate the validity of the proposed method is presented. © 2010 IEEE.

This paper investigates the scalability of a parallel fast multipole accelerated boundary integral equation method in electrostatic field analyses. A load balancing technique suitable for highly parallel computation with 100 or more processes is also proposed. Numerical results clarify the effectiveness of the developed method in practical models with complicated geometry. © 2010 IEEE.

This paper investigates the procedure for starting a rotation sensorless PMSM under coasting condition for railway vehicle traction. To achieve restarting, the initial rotor position and speed at restart are needed. The existing algorithm for estimation of the initial position and speed cannot be applied to railway vehicle traction because of the greater speed range and the longer current sampling time. We propose a novel method for estimation of the initial speed. The estimation method is verified experimentally to assure that it is suitable for application to the railway vehicle traction system. (C) 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 169(2): 56-63, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20764

This paper proposes novel techniques for the improvement of the convergence characteristic of step-by-step time integrations in nonlinear transient eddy-current analyses. The proposed methods, which are based on the time-periodic finite-element method and the explicit error correction method, can extract poorly-converged error components corresponding to large time constants of an analyzed system. The correction of the extracted error components accelerates the convergence of transient calculation efficiently. Furthermore, we extend the performance of the proposed methods in nonlinear problems. Some numerical results that verify the effectiveness of the proposed methods are also presented. © 2009 The Institute of Electrical Engineers of Japan.

Recently, the total number of distributed generators (DGs) Such as photovoltaic generation system and wind turbine generation system connected to an actual distribution network has increased drastically. The distribution network connected to many distributed gerators must be operated keeping reliability of power supply, power quality, and loss minimization. In order to accomplish active distribution network operation to take advantage of many connections of DGs, a new coordinated operation of distribution system with many connections of DGs is necessary. In this paper, the authors propose a coordinated operation of distribution network system connected to many DGs by using newly proposed sectionalizing switch control, sending voltage control, and computation of available DG connection capability. In order to check the validity of the proposed coordinated operation of distribution system, numerical simulations using the proposed coordinated distribution system operation are carried out in a practical distribution network model. (C) 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(3): 46-57, 2009; Published online in Wiley InterScience (www.interscience.wiley. com). DOI 10.1002/eej.20655

This paper describes a large-scale micromagnetic simulation by using the fast multipole method (FMM) specialized for uniform brick elements. The fast Fourier transform (FFT) is widely used to reduce computational costs of the demagnetizing field calculation. However, the FFT still requires operation counts of O(N log N), where N is the number of elements, which results in the huge computational costs in large-scale problems. To overcome the difficulties, we develop an O(N) approach based on the FMM. In a micromagnetic simulation, an analyzed region is usually subdivided into uniform elements. By making the best use of the periodic structure of uniformly distributed elements, the computational costs of the FMM can be reduced drastically. A large-scale micromagnetic simulation of a single-pole-type head demonstrates the effectiveness of the specialized FMM from the viewpoints of calculation time and memory requirements, compared with the FFT. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3068012]

This paper describes a large-scale micromagnetic simulation by using the fast multipole method (FMM) specialized for uniform brick elements. The fast Fourier transform (FFT) is widely used to reduce computational costs of the demagnetizing field calculation. However, the FFT still requires operation counts of O(N log N), where N is the number of elements, which results in the huge computational costs in large-scale problems. To overcome the difficulties, we develop an O(N) approach based on the FMM. In a micromagnetic simulation, an analyzed region is usually subdivided into uniform elements. By making the best use of the periodic structure of uniformly distributed elements, the computational costs of the FMM can be reduced drastically. A large-scale micromagnetic simulation of a single-pole-type head demonstrates the effectiveness of the specialized FMM from the viewpoints of calculation time and memory requirements, compared with the FFT. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3068012]

In this paper, we describe the applicability of Algebraic Multigrid Method (AMG method) as a fast solution for magnetic field analysis of an electric machine with a laminated core. In an experimental analysis, we have found that there are some cases where the calculation speed can be improved by using the AMG method for a fine mesh that models a laminated iron core exactly. Therefore we investigated the convergence characteristic of the standard Incomplete Cholesky Conjugate Gradient method (standard ICCG method) and the Conjugate Gradient method preconditioned with AMG method (AMGCG method) for the simple and actual analysis models. The numerical results show that the AMGCG method provides fast solutions for laminated mesh models for which the standard ICCG method does not work well in many analysis cases.

This paper reports a large-scale eddy-current analysis of conductive frame of large-capacity inverter. The eddy-current loss obtained by the electromagnetic field analysis is used as a heat source for the thermal analysis. Then, the suitable configuration of the frame for the suppression of temperature increase is investigated and designed. The hybrid finite-element and boundary-element (FE-BE) method is very suitable for the analysis of a complicated-shaped frame because it does not require mesh division for a free space and can easily treat eddy current. For the reduction of large computational costs, the fast multipole method (FMM) is introduced. Furthermore, in order to improve the convergence characteristic of iterative methods for system matrix, we develop the application of the IDR(s) method to the minor iterative preconditioning technique (MIP) and evaluate the performance. Finally, some numerical results that demonstrate the effectiveness of the developed method are presented.

This paper investigates a starting procedure of rotational sensorless permanent magnet synchronous motor (PMSM) in the rotating condition, which is suitable for some applications with higher maximum rotor frequency and longer current sampling time. Instantaneous estimation of initial rotor position and frequency, right after gates start, is essential for restarting the operation of inverters. Existing estimation methods are not available for the aforementioned applications because of their higher maximum rotor frequency and longer current sampling time. To cope with this problem, we propose a novel initial rotor frequency estimation method. The proposed estimation method is verified by experiments using a 2-kW interior PMSM and a numerical simulation.

In this study, we examine the relationship between harmonic voltage injection, acoustic noise, and position estimation performance in a PMSM when a position-sensorless control method involving harmonic voltage injection is used at low speeds. Further, we propose a novel control method for voltage injection
this method can be used to reduce acoustic noise in the motor. The proposed control method is verified by performing numerical simulations and carrying out experiments using a 4-pole, 2-kW, 2100-rpm IPMSM (interior permanent-magnet synchronous motor). © 2009 The Institute of Electrical Engineers of Japan.

This paper investigates a starting procedure of rotational sensorless permanent magnet synchronous motor (PMSM) in the rotating condition, which is suitable for some applications with higher maximum rotor frequency and longer current sampling time. Instantaneous estimation of initial rotor position and frequency, right after gates start, is essential for restarting the operation of inverters. Existing estimation methods are not available for the aforementioned applications because of their higher maximum rotor frequency and longer current sampling time. To cope with this problem, we propose a novel initial rotor frequency estimation method. The proposed estimation method is verified by experiments using a 2-kW interior PMSM and a numerical simulation.

This paper proposes a novel robust optimization approach by combination of sensitivity analysis and sigma level estimation in multi-objective problems. In order to obtain robust Pareto-optima within acceptable computational costs, we actively reuse the already calculated data for the sensitivity analysis in multipoint search algorithm. The sigma level estimation is also utilized to select the significant solutions from a large number of Pareto-optima based on both the robustness and the performance. Some numerical results that verify the effectiveness of the proposed methods are presented.

This paper describes an iron-loss analysis of permanent-magnet synchronous motor (PMSM) taking into account lamination of iron core by a finite-element method (FEM) with a homogenization method. The detailed modeling of the laminated structure by the FEM with gap elements and double nodes requires a huge number of elements, which results in the limitation of the problem size. In order to reduce the computational costs, we apply the homogenization method to iron-loss analyses of a skewed interior PMSM and a surface permanent-magnet motor with overhanging magnet. For the clarification of the effectiveness, the homogenization method is compared with the detailed modeling from the viewpoints of computational costs and accuracy. As a consequence, it is verified that the homogenization method can analyze magnetic fields in a laminated iron core of a practical electric machine within acceptable computational costs.

This paper describes an iron-loss analysis of permanent-magnet synchronous motor (PMSM) taking into account lamination of iron core by a finite-element method (FEM) with a homogenization method. The detailed modeling of the laminated structure by the FEM with gap elements and double nodes requires a huge number of elements, which results in the limitation of the problem size. In order to reduce the computational costs, we apply the homogenization method to iron-loss analyses of a skewed interior PMSM and a surface permanent-magnet motor with overhanging magnet. For the clarification of the effectiveness, the homogenization method is compared with the detailed modeling from the viewpoints of computational costs and accuracy. As a consequence, it is verified that the homogenization method can analyze magnetic fields in a laminated iron core of a practical electric machine within acceptable computational costs.

This paper describes a large-scale magnetic field analysis by means of the hybrid finite element-boundary element (FE-BE) method. The hybrid FE-BE method is well-suited for solving open electromagnetic field problems that comprise movement, nonlinear media, and eddy current. In general, however, large memory and computational costs are required due to the dense blocks in the system matrix generated by the BE part of the hybrid formulation. In order to overcome the above difficulties, we introduce the fast multipole method (FMM) to the hybrid FE-BE formulation developed by ourselves. Furthermore, we propose a novel preconditioning technique suitable for the hybrid FE-BE method with the FMM. Some numerical results that demonstrate the effectiveness of the proposed approach are also presented. (c) 2007 Wiley Periodicals, Inc.

For the speed sensor-less control in the ultra lower speed range, the mechanical simulator method is applied to cope with the problems due to the extremely lower induced voltage. In the method, however, the mechanical parameters' error, such as the error of the inertia, affects the starting performance. To reveal the conditions for the stable starting, we carry out the phase plane analysis under the condition that the actual inertia J changes from the set inertia J(s). Consequently, we find out J(s) &gt;= J is the condition for the stable acceleration. The derived condition is useful as a design index of the mechanical simulator. Additionally, to cope! with the large variation of the inertia, we carry out the phase plane analysis of the IM simulator method which compensates the estimation error of the rotor frequency. The analysis reveals that the method enables the stable acceleration while the estimation error of speed is remained in the case of inertia variation. Furthermore, we propose the modified IM simulator method which eliminates the deviation. By the phase plane analysis and experimental tests, we confirm the effectiveness of modified method.

New method to estimate electromagnetic screening effect of rigid frame viaducts has been developed. Mutual relationship among the effects of electrical connecting manner of girding bridges
conductivity of the ground
and harmonic frequency was identified theoretically and numerically based on the results of multiple conductor circuit model simulations and field measurements using over 3km length test cables set on a viaduct section of Shinkansen line under construction. Adding, developed modeling method to simplify the equivalent circuit of vast amount of steel bars in the reinforced concrete accelerates the estimation process with enough accuracy. As the result, it became easy to calculate the induced voltage in the cables or in the track circuits with enough accuracy. © 2008 The Institute of Electrical Engineers of Japan.

The power source of hybrid railway vehicles consists of both generation and energy storage devices. The hybrid vehicles have a high degree of freedom in the system design because they have different power sources. Therefore, it is difficult to establish generalized design methods of the power system. Various patterns of device capacities of generation and energy storage equipments are available for the hybrid vehicle. And various types of power control strategies are also selectable. With this background, this paper proposes a globally searched design estimation method for hybrid vehicles, which is based on multiobjective optimization by dynamic programming. The proposed method enables us to globally clarify the optimal candidates in accordance with various railway lines from a wide search domain. This results in various design concepts of the hybrid vehicles. Then, this paper confirms that the proposed method provides effective design guidelines for the conceptual design of the hybrid vehicles. Therefore the proposed method is useful for the design problem of hybrid vehicles that have a higher degree of freedom compared to electric railway vehicles. (C) 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

To reduce the fluctuation of wind power output by installing storage batteries to wind power generation, accurate estimation of wind power is indispensable. Calculation based on Power Curve, general method to estimate wind power output, often causes unavoidable error due to influences of time fluctuation of wind speed and direction. Therefore, we propose to apply Just-In-Time (JIT) Modeling to the estimation and the forecast of wind power output. JIT Modeling has the advantage that the algorithm is relatively simple. Compared with another non-linear modeling method, we confirmed the validation of JIT Modeling against the estimation and forecasts of wind power output through computational simulations.

For the spread of wind power generations, the technology of reducing fluctuations in wind power output is indispensable. In this research, we perform computational analyses of a wind power generation system with storage battery, and propose a novel approach for deriving the proper battery capacity. This research is to achieve sufficient smoothing of wind power output and efficient use of wind power energy. In the proposed method, numerically investigating the trade-off relationship among the smoothing effect, battery capacity, and output efficiency characteristics, we can derive the battery capacity on the basis of cost/performance. Furthermore, we performed the investigation of the system using wind power prediction method, i.e., Just-In-Time Modeling. By predicting the wind power output, we can properly update the smoothing time constant according to the short-term wind condition, which results in the reduction of battery capacity. To verify the proposed approach, we also present some computational results based on the measured data of small wind power generation system.

This paper describes a benchmark model proposed for the clarification of the characteristic of various methods for modeling the laminated iron core. In order to obtain a reference solution of the benchmark model, a large-scale non-linear magnetostatic field analysis with a fine mesh enough to represent the microscopic structure of the laminated iron core is carried out by using the hybrid finite element-boundary element (FE-BE) method combined with the fast multipole method (FMM) based on diagonal forms for translation operators. The computational costs and accuracy of two kinds of the homogenization methods are discussed comparing the reference solution. As a consequence, it is verified that the homogenization methods can analyze magnetic fields in laminated iron core within acceptable computational costs.

This paper investigates starting procedure of rotation sensorless PMSM at coasting condition for railway vehicle traction. To realize the restarting, the initial rotor position and speed at restart are needed. The existing estimation algorithm of the initial position and speed can&#039;t be applied to railway vehicle traction because of the higher speed range and the longer current period. We propose novel estimation method of the initial speed, The estimation method is verified experimentally to ensure that it is feasible enough to be applied to the railway vehicle traction system.

This paper describes a benchmark model proposed for the clarification of the characteristic of various methods for modeling the laminated iron core. In order to obtain a reference solution of the benchmark model, a large-scale nonlinear magnetostatic field analysis with a fine mesh enough to represent the microscopic structure of the laminated iron core is carried out by using the hybrid finite element-boundary element (FE-BE) method combined with the fast multipole method (FMM) based on diagonal forms for translation operators. The computational costs and accuracy of two kinds of the homogenization methods are discussed comparing the reference solution. As a consequence, it is verified that the homogenization methods can analyze magnetic fields in laminated iron core within acceptable computational costs.

This paper investigates starting procedure of rotation sensorless PMSM at coasting condition for railway vehicle traction. To realize the restarting, the initial rotor position and speed at restart are needed. The existing estimation algorithm of the initial position and speed can't be applied to railway vehicle traction because of the higher speed range and the longer current period. We propose novel estimation method of the initial speed. The estimation method is verified experimentally to ensure that it is feasible enough to be applied to the railway vehicle traction system.

This paper shows a large-scale and highly accurate nonlinear magnetostatic field analysis of laminated iron core by using the hybrid finite element and boundary element (FE-BE) method. The hybrid FE-BE method is fairly effective to directly deal with the microstructure because no mesh division is required for the free space. In order to obtain the drastic reduction of the computational costs and stabilize the convergence characteristic of the Newton-Raphson method, the fast multipole method and the line search are introduced. Some numerical results that verify the effectiveness of the developed method are also presented.

In this paper we report advancement of an analysis method for electromagnetic screening effect of mountain tunnel I with a multiple conductor circuit model. On A.C. electrified railways it is a great issue to manage the influence of electromagnetic induction caused by feeding circuits. Tunnels are said to have a screening effect to reduce the electromagnetic induction because a large amount of steel is used in the tunnels. But recently the screening effect is less expected because New Austrian Tunneling Method (NATM), in which the amount of steel used is less than in conventional methods, is adopted as the standard tunneling method for constructing mountain tunnels. So we measured and analyzed the actual screening effect of mountain tunnels constructed with NATM. In the process of the analysis we have advanced a method to analyze the screening effect more precisely. In this method we can adequately model tunnel structure as a part of multiple conductor circuit.

In this paper we report advancement of an analysis method for electromagnetic screening effect of mountain tunnel with a multiple conductor circuit model. On A.C. electrified railways it is a great issue to manage the influence of electromagnetic induction caused by feeding circuits. Tunnels are said to have a screening effect to reduce the electromagnetic induction because a large amount of steel is used in the tunnels. But recently the screening effect is less expected because New Austrian Tunneling Method (NATM), in which the amount of steel used is less than in conventional methods, is adopted as the standard tunneling method for constructing mountain tunnels. So we measured and analyzed the actual screening effect of mountain tunnels constructed with NATM. In the process of the analysis we have advanced a method to analyze the screening effect more precisely. In this method we can adequately model tunnel structure as a part of multiple conductor circuit.

This paper proposes the variables screening technique based on the stepwise multiple regression in multiobjective design optimization. This approach enables us to efficiently select the design variables that have a sufficient effect on machine performance. Some numerical results that demonstrate the validity of the proposed method are also presented.

This paper describes large-scale and fast nonlinear magnetostatic field analyses by the magnetic moment method (MMM) with the adaptive cross approximation. In order to stabilize the convergence characteristic of the Newton-Raphson method, we apply a line search technique to the MMM. Some numerical results that demonstrate the validity of the developed method are also presented.

This paper examines the relationship among injected harmonic voltage, acoustic noise, and position estimation error in a position sensorless control method at low speed range using harmonic voltage injection. Moreover, a novel injected voltage control method for reducing the acoustic noise is proposed. The proposed control method is verified by numerical simulations and experiments using a 4-pole, 2 kW, 2 100 rpm mini model test prototype.

In this study, we analyze energy consumption of FC-EDLC hybrid railway vehicle to reveal the energy reduction effect. To evaluate this effect properly, we adopt dynamic programming which is optimal control theory. Dynamic programming enables us to calculate energy consumption under optimized control of power sources. In this paper, we evaluate the relationship among reduction effect of energy consumption, device capacity, and line profiles. Finally, we reveal the energy consumption characteristics and the applicability of hybrid-power-source railway vehicle.

This paper presents the theoretical studies on the DC-link current harmonics in the inverter-controlled DC electric railcar. First, we derive the mathematical expression of the harmonics. And comparison among a theoretical result, a numerical simulation result, and an experimental result is also presented for verification of the proposed theoretical analysis. Then this paper examines the harmonic cancellation effect of the phase shift operation by the derived mathematical expression.

In this paper, we study an optimal design for a hybrid power source railway vehicle as an alternative to diesel railway vehicles. The hybrid power source railway vehicle is assumed to be composed of the fuel cell and the electric double layer capacitor. We apply the multiobjective optimization based on the genetic algorithm for the vehicle design, aiming at reduction of both initial cost and energy consumption. The pareto optimal solutions are obtained using the multiobjective optimization. First we develop a simulation model of the hybrid power source railway vehicle and its electric power control methods. Next we derive the pareto optimal solutions as a result of the multiobjective optimization. Finally, we categorize the pareto optimal solutions to some groups, which enables us to elucidate characteristics of the pareto optimal solutions. Consequently, using the multiobjective optimization approach we effectively comprehend the problem characteristics and can obtain the plural valuable solutions.

In order to reduce the fluctuation of wind power output, researches on installation of storage batteries to wind power generation have been conducted. But in order to efficiently perform the charge and discharge control of storage battery, accurate estimation of wind power is required. Generally, power curve, a characteristic curve of wind power output vs. wind speed, is used for the estimation. In our research, we propose a simple and high-precision modeling method (Just-In-Time Modeling). Finally, Just-In-Time Modeling is further proved to be a more effective method through computational simulations: short-term forecasts are also discussed.

In this paper, we study an optimal design for a hybrid power source railway vehicle as an alternative to diesel railway vehicles. The hybrid power source railway vehicle is assumed to be composed of the fuel cell and the electric double layer capacitor. We apply the multiobjective optimization based on the genetic algorithm for the vehicle design, aiming at reduction of both initial cost and energy consumption. The pareto optimal solutions are obtained using the multiobjective optimization.<br>First we develop a simulation model of the hybrid power source railway vehicle and its electric power control methods. Next we derive the pareto optimal solutions as a result of the multiobjective optimization. Finally, we categorize the pareto optimal solutions to some groups, which enables us to elucidate characteristics of the pareto optimal solutions. Consequently, using the multiobjective optimization approach we effectively comprehend the problem characteristics and can obtain the plural valuable solutions.

This paper describes a large-scale and highly accurate magnetostatic field analysis targeting a magnetic shield. The hybrid finite element-boundary element method and the magnetic moment method do not require mesh division for the free space and can easily treat the nonlinearity of magnetic property. Therefore, these methods are considered very effective for the analysis of a magnetic shield which has a high aspect ratio of the size scale to the thickness. However, large memory and computational time have been required due to the dense matrices generated by those integral-based formulations. To overcome the difficulties, we introduce the fast multipole method into the hybrid method and the magnetic moment method. Furthermore, to achieve more reduction of CPU time, we propose an effective preconditioning technique suitable for the hybrid method. Some numerical results that demonstrate the effectiveness of these approaches are also presented. (C) 2006 American Institute of Physics.

This paper describes an approach to efficient modeling of the microscopic structure of magnetic materials in the nonlinear magnetostatic field analysis of a laminated core. When the ordinary finite element method is applied, large memory and computational cost are required due to the huge number of elements generated by detailed modeling of a laminated core. In order to overcome the above difficulties, we introduce the homogenization method, which is widely used in continuum mechanics, into the magnetic field computation and expand the method into the nonlinear analysis. Furthermore, the specialized homogenization method for a laminated core is carried out to verify the above homogenization method in the electromagnetism. Some numerical results are also presented to demonstrate the effectiveness of the proposed method. (C) 2006 American Institute of Physics.

This paper describes an approach to efficient modeling of the microscopic structure of magnetic materials in the nonlinear magnetostatic field analysis of a laminated core. When the ordinary finite element method is applied, large memory and computational cost are required due to the huge number of elements generated by detailed modeling of a laminated core. In order to overcome the above difficulties, we introduce the homogenization method, which is widely used in continuum mechanics, into the magnetic field computation and expand the method into the nonlinear analysis. Furthermore, the specialized homogenization method for a laminated core is carried out to verify the above homogenization method in the electromagnetism. Some numerical results are also presented to demonstrate the effectiveness of the proposed method. (C) 2006 American Institute of Physics.

This paper describes a large-scale and highly accurate magnetostatic field analysis targeting a magnetic shield. The hybrid finite element-boundary element method and the magnetic moment method do not require mesh division for the free space and can easily treat the nonlinearity of magnetic property. Therefore, these methods are considered very effective for the analysis of a magnetic shield which has a high aspect ratio of the size scale to the thickness. However, large memory and computational time have been required due to the dense matrices generated by those integral-based formulations. To overcome the difficulties, we introduce the fast multipole method into the hybrid method and the magnetic moment method. Furthermore, to achieve more reduction of CPU time, we propose an effective preconditioning technique suitable for the hybrid method. Some numerical results that demonstrate the effectiveness of these approaches are also presented. (C) 2006 American Institute of Physics.

This paper shows large-scale eddy-current analysis by a hybrid finite-element and boundary-element (FE-BE) method. We introduce the fast multipole method (FMM) into the two kinds of hybrid FE-BE formulations developed by ourselves. To achieve more reduction of CPU time, we propose a novel preconditioning technique suitable for the hybrid FE-BE methods with the FMM. Furthermore, we improve the FMM calculation process in the hybrid method using magnetic field intensity. Some numerical results that demonstrate the effectiveness of these approaches are also presented.

This paper describes large-scale magnetic field analysis by means of the hybrid finite element-boundary element (FE-BE) method. The FE-BE method is well-suited for solving open electromagnetic field problems that comprise movement, non-linear media and eddy current. In general, however, large memory and computational costs are required due to the dense blocks in the system matrix generated by the BE part of the hybrid formulation. To overcome the above difficulties, we introduce the fast multipole method (FMM) to the FE-BE formulation developed by ourselves. Furthermore, we propose a novel preconditioning technique suitable for the hybrid FE-BE method with the FMM. Some numerical results that demonstrate the effectiveness of the proposed approach are also presented.

This paper describes large-scale magnetic field analysis by means of the hybrid finite element-boundary element (FE-BE) method. The FE-BE method is well-suited for solving open electromagnetic field problems that comprise movement, non-linear media and eddy current. In general, however, large memory and computational costs are required due to the dense blocks in the system matrix generated by the BE part of the hybrid formulation. To overcome the above difficulties, we introduce the fast multipole method (FMM) to the FE-BE formulation developed by ourselves. Furthermore, we propose a novel preconditioning technique suitable for the hybrid FE-BE method with the FMM. Some numerical results that demonstrate the effectiveness of the proposed approach are also presented.

The harmonics of the return current may interfere with the signaling current along with the rails. In this paper, we present the theoretical studies of the return current harmonics in the inverter-controlled DC electric railcar, aiming at contributing future work to improve the compatibility with the signaling current. We theoretically derive sideband harmonics of the DC-link current. Then, in order to verify the theoretical study, we experimentally measure the harmonics and numerically simulate the harmonics. As a result, we concluded the theoretical DC-link current is enough accurate to be utilized for the future improvement of the inverter harmonics current.

This paper proposes the variables screening technique based on the stepwise multiple regression in multi-objective design optimization. This approach enables us to efficiently select the design variables that have a sufficient effect on machine performance. Some numerical results that demonstrate the validity of the proposed method are also presented. ©2006 IEEE.

This paper describes large-scale and fast nonlinear magnetostatic field analyses by the magnetic moment method with the adaptive cross approximation (ACA). To stabilize the convergence characteristic of the Newton-Raphson method, a line search technique is also applied. Some numerical results that demonstrate the validity of the developed method are presented. © 2006 IEEE.

The voltage of the distribution line in the district where the PV systems are clustered will be raised by reversal power flow from the PVs. Then active power control of the PV systems depresses the output. So, installing storage battery stations in the clustered PV systems is one of the means to solve the problem. Therefore, we investigated proper arrangement and control of the storage battery stations for effective utilization of the electric power generated by the PV clusters. In this paper, by means of computational simulation, we quantitatively revealed the relationship between the total amount of the storage battery capacity, the reduction rate of PV output, and the arrangement of the storage battery stations.

This paper concerns a Photovoltaic / Diesel Generator hybrid power generation system with storage battery. Utilizing computational optimization methods, we carry out the optimum diesel generator operation and charge-discharge control of storage battery from the viewpoint of fuel consumption.
Some numerical results, that demonstrate the validity of the proposed technique, are also presented. The derived trade-off relationship between the minimized fuel consumption and PV-battery capacities is useful for the design of hybrid system as quantitative indices.

This paper investigates a new flux-weakening operation of interior permanent magnet synchronous motors for railway vehicle traction. A design method of the controller is also suggested. The control method is verified both numerically and experimentally to ensure that it is feasible enough to be applied to the railway vehicle traction system.

This paper shows a large-scale analysis of surface charge in eddy-current problems, which is useful for designing an electric machine. We introduce the fast multipole method with the pseudoparticle method into the large-scale surface charge analysis and further propose an approach to dealing with the symmetry and periodicity of the analysis model by the concept of the method of images. Some numerical results, which will show the validity of the proposed method that calculation time is reduced while maintaining high precision, are presented.

In this article, in order to investigate the merits of three-dimensional (3D) equivalent magnetic circuit network (EMCN) method, a 3D standard benchmark model proposed by the Institute of Electrical Engineers of Japan is analyzed. We also examine the accuracy of analysis results, the computer storage, and the computation time through the systematical comparison between 3D EMCN method and 3D finite element method based on hexahedral edge element. The incomplete Cholesky conjugate gradient method was selected for the solver. From the results, we can confirm the usefulness of 3D EMCN method. (c) 2005 American Institute of Physics.

The permanent magnet synchronous motor (PMSM) is an efficient machine, which has found application over wide power and speed ranges. This paper presents the optimal rotor design of a PMSM for use on a railway vehicle. This design utilizes reluctance torque in order to develop higher torque at starting with low open circuit voltage at high speed. © 2004, The Institute of Electrical Engineers of Japan. All rights reserved.

In this paper, we discuss multiobjective design optimization of brushless permanent magnet motor (BLPMM) solved by genetic algorithm (GA) and 3D equivalent magnetic circuit network (EMCN) method. In the multiobjective optimization (MO) problem, we choose the decrease of cogging torque and the increase of torque as objectives. The airgap length, teeth width and magnetization angle of permanent magnet (PM) are also selected for the design variables respectively. From the results, our approach method enabled us to efficiently obtain diverse Pareto optimal (PO) solutions from the practical point of view. The experimental results are shown to confirm the validity of the optimization results.

In this paper, we propose a computational approach to the design of an interior permanent magnet synchronous motor to clarify its optimal design applied for traction systems of the next generation commuter train. In the approach, the finite element method, the multiobjective optimization technique, and the response surface methodology are effectively introduced. This approach enables us to save the CPU-time dramatically without degrading accuracies. Additionally, the proposed approach provides the effective information to design engineers. Finally we validate the proposed approach.

The harmonics of the return current may interfere with the signaling current along with the rails. In order to investigate the index of the compatibility with the signaling current, the theoretical investigation of the return current harmonics is preferable rather than expensive and time consuming experimental study.
In this paper, we present the theoretical studies of the return current harmonics with the asynchronous type two-step PWM in the inverter-controlled DC electric railcar, aiming at contributing future work to improve the compatibility with the signaling current.
We analyze the return current harmonics by the following two methods. The first one is to derive theoretically the return current harmonics with the motor current harmonics approximation. The second one is to simulate numerically a traction circuit including a inverter and a motor, in order to verify theoretically derived return current. Comparing the both results, we concluded the theoretical return current is enough accurate to be utilized for the future improvement of inverter harmonics current.

In this paper, a novel field-weakening scheme which is combined with a saturated voltage control strategy is proposed and its performance comparison with the previous scheme (without implementing the saturation strategy) is presented. Though the proposed scheme is quite simple, it is effective to provide a higher torque capability than the previous scheme does. The maximum torque is produced by increasing the flux-producing current as much as possible while the stator voltage reference is saturated. The voltage saturation condition is stimulated by adding the torque-producing current into the flux-producing current reference. Since the DC voltage utility can be improved, that hence, improve the output power in the high speed motor operation, a larger torque is produced. Experiments were carried out to verify the proposed scheme. The experimental results of the previous scheme are also presented for comparison purposes.

The harmonics of the return current may interfere with the signaling current along with the rails. In order to investigate the index of the compatibility with the signaling current, the theoretical investigation of the return current harmonics is preferable rather than expensive and time consuming experimental study.
In this paper, we present the theoretical studies of the return current harmonics with the asynchronous type two-step PWM in the inverter-controlled DC electric railcar, aiming at contributing future work to improve the compatibility with the signaling current.
We analyze the return current harmonics by the following two methods. The first one is to derive theoretically the return current harmonics with the motor current harmonics approximation. The second one is to simulate numerically a traction circuit including a inverter and a motor, in order to verify theoretically derived return current. Comparing the both results, we concluded the theoretical return current is enough accurate to be utilized for the future improvement of inverter harmonics current.

To estimate the characteristics of electric machines that have conductors of complicated shape, it is effective to analyze the surface charge related to eddy current phenomena. However, the eddy current field is generally treated as a quasi-static field in which the displacement current is neglected and the electric field is not defined in the nonconductive region in the calculation process. Therefore, when we use only theA-phi finite element method (FEM) as a field analysis method, it is difficult to calculate the surface charge directly at the interface between conductive and nonconductive regions. In this paper, with this background, we propose a novel method of analysis of the surface charge based on both the A-phi FEM with edge elements and the integral equation. This approach enables us to precisely calculate the surface charge. Some numerical results that demonstrate the validity of the proposed method are also presented, such as the surface charge analysis of linear induction motors for evaluating the relationships among the surface charge, eddy current, and conductor shape. (C) 2003 Wiley Periodicals, Inc.

This article presents a fundamental study on the application of the response surface methodology to design optimization of electric machines as an effective computational approach. As usual, in designing electric machines, it is difficult to achieve an effective optimal solution by using the FEM within an acceptable CPU-time. In this article, the response surface methodology (RSM) is introduced into the design optimization approach to evaluate the objective physical quantities in much shorter time. In the RSM process, to achieve the high quality optimal solutions, it is very important to make the response surface of high quality approximation in search domains. For that reason, Design of Experiments (DOE) is applied to obtain the appropriate selections of the FEM calculating points. Additionally, the effective iterative approach is developed, which properly narrows the search domains around the solution candidates. The proposed optimization approach results in an overall increase in the optimization speed without degrading the quality of optimal solutions. Some numerical examples that demonstrate the validity of the proposed approach are also presented. © 2003, The Institute of Electrical Engineers of Japan. All rights reserved.

This paper proposes a surface-charge analysis method for evaluating the characteristics of electric machines. The proposed method is based on both the three-dimensional A - phi edge finite-element method (FEM) and the boundary integral equation-method. In the proposed method, we impose the Coulomb gauge condition on the scalar potential derived from A - phi edge FEM. Some numerical results that demonstrate,the validity of the proposed method are also presented.

This paper investigates the permanent magnet overhang effect in brushless de motor., The characteristics are analyzed according to the variation of symmetric overhang length and asymmetric overhang ratio. A three-dimensional equivalent magnetic circuit network (EMCN) method is used for the accurate and efficient analysis. From the results, it is quantitatively verified that the increase of overhang length enhances the linkage fluxes of the stator and the asymmetric overhang ratio has a large effect, on the axial magnetic force.

As usual, brushless dc motor (BLDCM) has the overhang structure of which permanent magnet (PM) length is longer than the stator's stack length. Specially, in case of asymmetric overhang, we have to pay attention to the choice of suitable overhang ratio of the lower to the upper overhang length because of the effect of the ratio on the magnetic forces. In this article, the magnetic force characteristics of BLDCM with the asymmetric overhang and the cap of the rotor are analyzed. A three-dimensional equivalent magnetic circuit network (EMCN) method is used for the efficient analysis of the magnetic field. The magnetic forces and torque are calculated by Maxwell's stress tensor. The variation of magnetic force characteristics is also analyzed according to the overhang ratio. From the results, when the overhang ratio is 0.38, the axial magnetic force characteristic could be improved remarkably. The validity of the analysis results is also clarified by comparison between calculated results and measured ones. (C) 2003 American Institute of Physics.

We have developed a novel computational simulator for a photovoltaic (PV) power generation system as an efficient design tool. The developed simulator enables us to predict the complicated performance of the whole PV system with high accuracy at short time intervals and evaluate the system quantitatively. In this paper, using the developed simulator, we quantitatively estimate the changes of PV current, battery voltage, battery discharging current, commercial supply current, and the period of practicable stand-alone operation, etc., according to the reduction of PV/battery capacity. To confirm the validity of the developed simulator, we compare the calculated values with measured ones. The computational results precisely agree with the measured values under various PV/battery capacity conditions. Furthermore, altering PV/battery capacity in the simulation, we successfully predict the system performance, e.g., the period of practicable stand-alone operation, and evaluate the PV system parameters. © 2003, The Institute of Electrical Engineers of Japan. All rights reserved.

We proposed a novel design method of PV/Wind/Wave hybrid power generation system, and have presented the validity of the system based on several simulation results([1]). By applying the proposed method, several systems were actually constructed. Furthermore, the proposed method has been also verified by the analysis based on the measured data.

In this papers for further popularizing PV systems, we propose to network and control plural dispersed PV systems in small-scale area arming to operate them against unstable weather and the complicated variation of load power. We investigate some system operation modes that enable us to realize their low dependence on commercial supply or economical benefits as added values. As for the system design approach, we examine the relation between the battery capacity and the degree of dependence on the commercial supply by computational simulation. We also consider the voltage regulation as a problem to be settled in designing the system. Experimentally clarifying the relation between the voltage and the power flow regulations in the networked system, we investigate the storage battery ability to be required for relaxation of voltage regulation.

This paper deals with the peak cut system composed of PV power generation and storage battery. Recently, the demand for electric power becomes much greater especially in summer. Therefore, cutting and shifting the peak power consumption attracts ever-increasing attention. The introduction of the peak cut system results in the extensive reduction of power charge.
In this paper, we investigate the effective design method of both PV and storage battery capacities in the system by means of computational simulation. Some numerical results are also presented to demonstrate the validity of the proposed method.

This paper deals with the peak cut system composed of PV power generation and storage battery. Recently, the demand for electric power becomes much greater especially in summer. Therefore, cutting and shifting the peak power consumption attracts ever-increasing attention. The introduction of the peak cut system results in the extensive reduction of power charge.
In this paper, we investigate the effective design method of both PV and storage battery capacities in the system by means of computational simulation. Some numerical results are also presented to demonstrate the validity of the proposed method.

We proposed a novel design method of PV/Wind/Wave hybrid power generation system, and have presented the validity of the system based on several simulation results([1]). By applying the proposed method, several systems were actually constructed. Furthermore, the proposed method has been also verified by the analysis based on the measured data.

In this papers for further popularizing PV systems, we propose to network and control plural dispersed PV systems in small-scale area arming to operate them against unstable weather and the complicated variation of load power. We investigate some system operation modes that enable us to realize their low dependence on commercial supply or economical benefits as added values. As for the system design approach, we examine the relation between the battery capacity and the degree of dependence on the commercial supply by computational simulation. We also consider the voltage regulation as a problem to be settled in designing the system. Experimentally clarifying the relation between the voltage and the power flow regulations in the networked system, we investigate the storage battery ability to be required for relaxation of voltage regulation.

To estimate characteristics of electric machines that have conductors with complex form, it is effective to analyze the surface charge concerned with eddy current phenomena. However, the eddy current field is generally treated as quasi-static field in which the displacement current is neglected and the electric field is not defined in the non-conductive region in the calculating process. Therefore, when we adopt only the A-Ø FE method as a field analysis method, it is difficult to directly calculate the surface charge at the interface between conductive and non-conductive regions. In this paper, with this background, we propose a novel analysis method of the surface charge based both on the A-Ø formulation of 3D edge FE method and on the integral equation. This approach enables us to precisely calculate the surface charge. Some numerical results, which demonstrate the validity of the proposed method, are also presented, e.g., the surface charge analysis of linear induction motors for evaluating the relationships among the surface charge, eddy current, and conductor shape. © 2002, The Institute of Electrical Engineers of Japan. All rights reserved.

This article proposes an effective computational approach to design optimization of an outer-rotor type permanent magnet synchronous motor. As usual, because of the complicated rotor configuration and the complex magnetic saturation effects, it is difficult to design the lightweight permanent magnet synchronous motor structure that makes good use of reluctance torque within an acceptable CPU time. In this article, we adopt the finite element method as a magnetic field analysis method and the genetic algorithms as a search method. Furthermore, the response surface methodology, which enables us to evaluate the objective physical quantities in a much shorter time, is introduced into the above methods in the proposed approach. This optimization approach results in an overall increase in the optimization speed, that is, substantial CPU time reduction in comparison with the case of a conventional one. Some numerical results that demonstrate the validity of the proposed approach are also presented. (C) 2002 American Institute of Physics.

We propose an optimization approach based on the estimation of permeability distribution, which enables us to make an effective objective function of optimization methods for the efficient design of magnetic devices. By the proposed approach, we can improve magnetic device characteristics by evaluating the deviation in the permeability distribution of the device as an objective function. In this approach, we separate the iron areas and calculate the permeability of each block to consider the permeability distribution. To verify the proposed approach, some numerical results, i.e., the shape optimization of ventilation holes in an induction motor, which demonstrate the validity of the proposed approach, are also presented. The optimization concept based on the estimation of permeability distribution is effective and can be readily applied to the practical design optimization of various magnetic devices. (C) 2002 American Institute of Physics.

In this paper, we propose a boundary structure for improving performances of single-sided linear induction motors. In this study, by adopting a three-dimensional finite element method, detailed phenomena at the boundary between secondary sections have been clarified from the viewpoint of propulsive force and secondary current distributions. Further, to suppress the aggravation of the characteristic caused by the secondary structural transition, we connect the secondary sections electrically. Finally, the propulsive force characteristic has been improved in spite of the existence of the boundary. (C) 2002 American Institute of Physics.

In this paper, we propose a boundary structure for improving performances of Single-sided Linear Induction Motors (SLIMS). In such machines, solid-plate conductors and back irons are usually used for secondary stators throughout operating regions. However, to take account of deformation due to thermal expansions, secondary stators are constructed from some sections of limited length. Therefore, a propulsive force characteristic declines when the primary armature crosses the boundary between secondary sections. In this study, by adopting a three-dimensional finite element method, detailed phenomena at the boundary between secondary sections have been clarified from the viewpoint of propulsive force and secondary current distributions. Besides the validity of calculated results is verified by the measured results. Further, to suppress the aggravation of characteristic caused by the secondary structural transition, we connect the secondary sections electrically. Finally, the propulsive force characteristic has been improved in spite of the existence of the boundary. © 2002, The Institute of Electrical Engineers of Japan. All rights reserved.

In analyzing electrical apparatus excited from a constant voltage source such as rotating machines by the time-stepping Finite Element method, undesirable initial values often cause a large number of iterations and thus result in a long computing time. In this paper, with this background, we propose a novel acceleration method that improves the convergence characteristics of the time-stepping FE analysis for a motor excited from a constant voltage source. The proposed method enables us to sufficiently reduce the computing time by providing appropriate initial values to unknowns. In the method, the primary and secondary currents of an induction motor in steady-state operation are precisely estimated by means of both the equivalent circuit of a motor and the initial transient waveform of the currents obtained by the FE analysis, Finally, some numerical results, which demonstrate the validity of the proposed method, are also presented. © 2002, The Institute of Electrical Engineers of Japan. All rights reserved.

This paper describes a simple way to utilize C MEX S-function in MATLAB/SIMULINK for motor vector control modeling and simulation purposes. C MEX S-function is a powerful block in SIMULINK that capable to describe a dynamic system written in C language and linked into MATLAB. Basically it is categorized into three minimum structures. It is possible to model and simulate a vector-controlled motor drive with only using combination of these structures. A memory block is used for eliminating an algebraic loop so that speeding up the simulation. Simulation results will be compared with experimental ones for validation.

In recent years the numerical design optimization of magnetic devices has been the focus of interest of many engineers. In designing the practical devices such as induction motors, we have to estimate many kinds of objective physical quantities in the optimization process: e.g. magnetic flux, eddy current, torque, etc. This makes it difficult to obtain the effective solution that achieves the high device performance boosts within an acceptable CPU time. Thus, some contrivances to the practical design optimization are indispensable according to the device characteristics. In this paper, with this background, we propose an effective approach to the design optimization of rotating machinery by using the numerical analysis combined with the analytical design methodology and physical considerations. To verify the proposed approach, some numerical results, i.e., the shape optimization of ventilation holes in an induction motor, are also presented. In the numerical example, our goal is to widen the ventilation hole area without making the influence of the rotor-yoke saturation more serious. © 2001, The Institute of Electrical Engineers of Japan. All rights reserved.

This paper describes a novel acceleration method that improves the convergence characteristics of the time-stepping finite element analysis for a rotating machine excited from a constant voltage source. In the proposed method, we utilize the equivalent circuit of a rotating machine and its transient current waveform characteristics. Some numerical results, which demonstrate the validity of the proposed method, are also presented.

The regenerative braking method has been employed in DC-fed electric railway vehicle traction system in order to reduce energy consumption. The load's power consuming is sometimes insufficient for the regenerated power, and it causes the input voltage of traction inverter rises. In such a case, the regenerative current is regulated to prevent the over voltage. However, in applying this regulation, especially to the permanent magnet synchronous motors (PMSM) traction system, a continuous oscillation of regenerative current is sometimes observed. Unfortunately, It deteriorates passengers' riding comfortability due to torque fluctuation. On this paper, we analyze the phenomena of the oscillation of regenerative currents and suggest an anti-oscillation regenerative current regulation method based on the analyzing results. The detail is as follows. (1) We construct a nonlinear time-varying model, which consists of the substation, power feeding system and the main traction circuit onboard and divide the nonlinear time-varying model into four linear time-invariant systems. (2) Through the analysis with the models, we make it clear that the continuouso scillationis caused by the traditional regenerative braking control method (3) Based on the analysis we suggest a novel anti-oscillation regenerative braking control method, whose effectiveness is proved through experiments. © 2001, The Institute of Electrical Engineers of Japan. All rights reserved.

In a conventional field oriented control of induction motor the rotor flux is assumed to be constant so that the torque is controlled by controlling the q-axis current only. In field-weakening region the rotor flux is decreased to achieve a very high rotor speed, as a consequence the available torque is reduced. In the other hand, to produce a maximum torque the rotor nux should be generated as much as possible. In this paper, a novel, simple field-weakening strategy, which provides a maximum torque capability for a sinusoidal PWM VSI-fed induction motor drive, is presented. The purpose of proposed strategy is to add the absolute q-axis current to d-axis current reference so that proper flux and torque for any given torque-producing current reference are produced automatically. The maximum torque when it is required can be obtained over the entire field-weakening region without using machine parameters or special control strategy. A saturated sinusoidal PWM is used which limits the amplitude of the inverter voltage references. As an advantage, the effective output voltage as seen by the motor is boosted. Simulation and experiment results verify the performance of the proposed method.

In a DC-fed motor drive system that implements a regenerative braking control strategy, the oscillation phenomenon in electrical system occurs due to the regenerative power regulating to prevent a DC-link over-voltage condition. In this paper the oscillation phenomenon of electrical system in the PMSM drive of railway vehicle system with a light-load regenerative braking control is pointed out. First, a simulation is carried out to confirm the oscillation phenomenon occurrence. The investigated model is then derived and its stability analysis is elucidated. Base on the analysis results a novel anti-oscillation strategy is proposed. A downsized experimental system is used for validation purpose. It Is verified that the proposed strategy eliminates the oscillation effectively.

In a DC-fed motor drive system that implements a regenerative braking control strategy, the oscillation phenomenon in electrical system occurs due to the regenerative power regulating to prevent a DC-link over-voltage condition. In this paper the oscillation phenomenon of electrical system in the PMSM drive of railway vehicle system with a light-load regenerative braking control is pointed out. First, a simulation is carried out to confirm the oscillation phenomenon occurrence. The investigated model is then derived and its stability analysis is elucidated. Base on the analysis results a novel anti-oscillation strategy is proposed. A downsized experimental system is used for validation purpose. It Is verified that the proposed strategy eliminates the oscillation effectively.

In a conventional field oriented control of induction motor the rotor flux is assumed to be constant so that the torque is controlled by controlling the q-axis current only. In field-weakening region the rotor flux is decreased to achieve a very high rotor speed, as a consequence the available torque is reduced. In the other hand, to produce a maximum torque the rotor nux should be generated as much as possible. In this paper, a novel, simple field-weakening strategy, which provides a maximum torque capability for a sinusoidal PWM VSI-fed induction motor drive, is presented. The purpose of proposed strategy is to add the absolute q-axis current to d-axis current reference so that proper flux and torque for any given torque-producing current reference are produced automatically. The maximum torque when it is required can be obtained over the entire field-weakening region without using machine parameters or special control strategy. A saturated sinusoidal PWM is used which limits the amplitude of the inverter voltage references. As an advantage, the effective output voltage as seen by the motor is boosted. Simulation and experiment results verify the performance of the proposed method.

This article describes a design optimization of an axially laminated rotor of the synchronous reluctance motor, using the optimization method combined with the magnetic field analysis. The magnetic flux distribution in the synchronous reluctance motor is distorted due to the complicated rotor configuration and the influence of magnetic saturation, which results in a large number of local minimum solutions. Therefore, taking account of the magnetic saturation by the finite element method, the authors propose a novel optimization approach by coupling the stochastic search method with the deterministic one. In the optimization process a suitable objective function for the stability of machine performances is also proposed. Finally some numerical results that demonstrate the validity of the proposed approach are presented. (C) 2000 American Institute of Physics. [S0021-8979(00)79808-2].

Providing against a power failure due to disasters, we have developed a photovoltaic power generation system as a back-up system for the optical network unit. Because of the restricted space in which the system is to be installed, in this paper, we intend to reduce the capacity of the developed PV system, especially the battery capacity. Considering the PV share and the commercial power supply share, we propose a novel control method of battery charging-discharging for the battery capacity reduction. According to the battery residual capacity, the control circuit manages the power flows in the system. First, we develop a precise computational simulator for the proposed system. Next, using the measured solar irradiance data, we investigate the system performances with the proposed control method by the simulator. Finally, some field trial results are also reported, which demonstrates the validity of the control method.

A novel hybrid drive that uses both linear induction motor (LIM) and linear synchronous motor (LSM) is presented. This motor consists of the primary winding energized by variable frequency supplies and the secondary having an additional solid-conductor besides the electromagnet. The effectiveness of the motor for practical use is demonstrated via experiment and finite element analysis.

This paper describes a modification of the full-order observer for the Sensorless IM Drive. The modified observer uses the rotor flux calculated by the flux model instead of estimating it, thus two of the four state equations can be removed. Implementation of the modified observer provides the performance improvement of the sensorless rotor flux oriented IM drive system. The validity of the modified observer is confirmed by experiments.

In information lines, copper wire cables have been replaced by optical fiber cables that cannot supply power to the optical network unit (ONU). Thus, in the case of disasters, communication function paralyses may take place. Therefore, the reliability of power supply to the ONU has become important in recent years. With this background, we have developed a PV system for the ONU. In the process of development, we have proposed a novel estimation method for PV systems, that enables us to easily grasp the relationship between the instruments in the system from an overall view by regarding the instruments as the black boxes and paying attentions only to Ehe energy flows. The proposed method is useful in determining the suitable parameter arrangement of the PV system. Utilizing the method, we developed lOW order PV systems and carried out the experimental operation for one year. The experimental results showed enough system performances to meet not only the design requirement but also the spatial constraint. © 2000, The Institute of Electrical Engineers of Japan. All rights reserved.

This paper evaluates the controller configurations for the application of the modified observer introduced in our previous paper A full load disturbance is applied to each configuration to observe the load effect. A simple speed estimation adjustment procedure to minimize the speed estimation error at the desired speed is proposed. All results, are carried out through experiments.

This paper evaluates the controller configurations for the application of the modified observer introduced in our previous paper A full load disturbance is applied to each configuration to observe the load effect. A simple speed estimation adjustment procedure to minimize the speed estimation error at the desired speed is proposed. All results, are carried out through experiments.

Providing against a power failure due to disasters, we have developed a photovoltaic power generation system as a back-up system for the optical network unit. Because of the restricted space in which the system is to be installed, in this paper, we intend to reduce the capacity of the developed PV system, especially the battery capacity. Considering the PV share and the commercial power supply share, we propose a novel control method of battery charging-discharging for the battery capacity reduction. According to the battery residual capacity, the control circuit manages the power flows in the system. First, we develop a precise computational simulator for the proposed system. Next, using the measured solar irradiance data, we investigate the system performances with the proposed control method by the simulator. Finally, some field trial results are also reported, which demonstrates the validity of the control method.

This paper describes a new simple speed estimator using fuzzy logic for improving the motor drive performance at low speed with low-resolution encoder. Since using fuzzy algorithm, the proposed technique requires no system parameter or assumption for speed estimation. Through the simulation and experiments, the proposed scheme enables to drive the motor at 25 rpm.

This paper describes a no, el approach to the design optimization of ventilation holes in induction motors. By investigating the relationship between the rotor-yoke configuration and the magnetic flux in the air-gap, we determine the desirable arrangement of ventilation holes. Some numerical results for a practical machine, which demonstrate the, validity of the proposed approach, are also presented.

This paper describes the stability analysis of the sensorless control system for permanent magnet synchronous motors using the reduced order observer. Deriving the equilibrium linearized state equation, we discuss the stability of the observer-based controller when the speed estimation error arises. The validity of the analysis results is confirmed by experiment.

This paper describes a no, el approach to the design optimization of ventilation holes in induction motors. By investigating the relationship between the rotor-yoke configuration and the magnetic flux in the air-gap, we determine the desirable arrangement of ventilation holes. Some numerical results for a practical machine, which demonstrate the, validity of the proposed approach, are also presented.

This paper describes a new simple speed estimator using fuzzy logic for improving the motor drive performance at low speed with low-resolution encoder. Since using fuzzy algorithm, the proposed technique requires no system parameter or assumption for speed estimation. Through the simulation and experiments, the proposed scheme enables to drive the motor at 25 rpm.

A large number of methods for the design optimization have been proposed in recent years. However, it is not easy to apply these methods to practical use because of many iterations. So, in the design optimization, physical and engineering investigation of the given model are very important, which results in an overall increase in the optimization speed. This paper describes a novel optimization procedure utilizing the conformal transformation method. This approach consists of two phases and has the advantage of grasping the physical phenomena of the model easily. Some numerical results that demonstrate the validity of the proposed method are also presented.

Recently, the request for the compactness of rotating machines such as traction motors has been increasing and thus the rotating machines should be of high power density. The compactness of motors makes the problem of the magnetic saturation more serious. With this background, this paper describes the design optimization of air-ducts in induction motors. By investigating the relationship between the rotor-yoke configuration with air-ducts and the magnetic flux density in the air-gap, we determine the desirable air-ducts arrangement. Some numerical results, which demonstrate the validity of the proposed approach, are also presented.

This paper presents a novel design approach composed of two sequential processes for 3D magnetic shielding problems, which results in the global optimum solution in a shorter time. The feature of the proposed approach is the adoption of the specific boundary element with permeability of infinity. Assuming the permeability of infinity enables us to regard the thickness of ferromagnetic shields as infinitesimal, and thus to simplify the investigated model adequately in numerical analysis. This reduces the number of unknown variables and saves us a large amount of CPU-time for grasping the broad characteristics of the model. Some numerical results that demonstrate the validity of the proposed approach are also presented.

Magnetic stimulation therapy without pain is being studied as an alternative to electrical stimulation therapy with pain. This paper presents a novel coil arrangement including the two sub-coils besides the main coil. This scheme results in the desired Bur distribution penetrating more deeply into the tissue. Each optimal coil current and the optimal sub-coil location are derived with the aid of numerical magnetic field analysis. The derivation is carried out by means of the genetic algorithm combined with the finite element method. Moreover, we incorporate the circuit equations with the above methods. The results suggest that the magnetic stimulation with plural coils is effective for the pudendal nerve in the deep site.

This paper presents a novel design approach composed of two sequential processes for 3D magnetic shielding problems, which results in the global optimum solution in a shorter time. The feature of the proposed approach is the adoption of the specific boundary element with permeability of infinity. Assuming the permeability of infinity enables us to regard the thickness of ferromagnetic shields as infinitesimal, and thus to simplify the investigated model adequately in numerical analysis. This reduces the number of unknown variables and saves us a large amount of CPU-time for grasping the broad characteristics of the model. Some numerical results that demonstrate the validity of the proposed approach are also presented.

This article describes the shape optimization of detective coils for initial rotor position estimation in the drive system of permanent magnet synchronous motors. The characteristics of magnetic circuits in rotating machinery are very complicated. The magnetic flux distribution in the air gap is nonsinusoidal due to the influence of slots, magnets, and magnetic saturation, etc. By utilizing the slot ripple influence and taking the effects of both magnetic saturation and permanent magnets into consideration, an optimization of the detective coil by means of a genetic algorithm combined with a hybrid finite element and boundary element method is reported. This produces a global optimal solution in a shorter time. (C) 1998 American Institute of Physics. [S0021-8979(98)50811-0].

A large number of methods for the design optimization have been proposed in recent years. However, it is not easy to apply these methods to practical use because of many iterations. So, in the design optimization, physical and engineering investigation of the given model are very important, which results in an overall increase in the optimization speed.
This paper describes a novel optimization procedure utilizing the conformal transformation method. This approach consists of two phases and has the advantage of grasping the physical phenomena of the model easily. Some numerical results that demonstrate the validity of the proposed method are also presented.

Novel approaches to the 3D optimal design of magnetic shields are presented, in which topology optimization is achieved with the aid of numerical magnetic field analysis. The numerical procedures are implemented by means of a genetic algorithm combined with hybrid finite element and boundary element methods. This results in an overall increase in the optimization speed with acceptable computational accuracy. Finally, we present numerical results that demonstrate the validity of the proposed approach. (C) 1998 Scripta Technica.

Novel approaches to the 3D optimal design of magnetic shields are presented, in which topology optimization is achieved with the aid of numerical magnetic field analysis. The numerical procedures are implemented by means of a genetic algorithm combined with hybrid finite element and boundary element methods. This results in an overall increase in the optimization speed with acceptable computational accuracy. Finally, we present numerical results that demonstrate the validity of the proposed approach. © 1998 Scripta Technica.

This article describes the shape optimization of detective coils for initial rotor position estimation in the drive system of permanent magnet synchronous motors. The characteristics of magnetic circuits in rotating machinery are very complicated. The magnetic flux distribution in the air gap is nonsinusoidal due to the influence of slots, magnets, and magnetic saturation, etc. By utilizing the slot ripple influence and taking the effects of both magnetic saturation and permanent magnets into consideration, an optimization of the detective coil by means of a genetic algorithm combined with a hybrid finite element and boundary element method is reported. This produces a global optimal solution in a shorter time. © 1998 American Institute of Physics.

In this paper we present a new approach to the sensor-less drive of permanent magnet synchronous motors based on the reduced order observer, First, we propose the new control inputs that decouple the d-axis current with the q-axis one. This enables us to construct the linear reduced order observer for estimating rotor speed and position. owing to the linearization of the motor model we can fix optimum gains of the observer under any operating condition. To confirm the validity of the proposed control scheme, experiments are carried out. The control is performed for the prototype of an eight-pole, 750W permanent magnet synchronous motor by using the software with DSP TMS320C31. The experimental results show high dynamic performance of the proposed control scheme.

Recently, the request for the compactness of rotating machines such as traction motors has been increasing and thus the rotating machines should be of high power density. The compactness of motors makes the problem of the magnetic saturation more serious. With this background, this paper describes the design optimization of air-ducts in induction motors. By investigating the relationship between the rotor-yoke configuration with air-ducts and the magnetic flux density in the air-gap, we determine the desirable air-ducts arrangement. Some numerical results, which demonstrate the validity of the proposed approach, are also presented. © 1998 IEEE REFERENCE.

Magnetic stimulation therapy without pain is being studied as an alternative to electrical stimulation therapy with pain. This paper presents a novel coil arrangement including the two sub-coils besides the main coil. This scheme results in the desired flux distribution penetrating more deeply into the tissue. Each optimal coil current and the optimal sub-coil location are derived with the aid of numerical magnetic field analysis. The derivation is carried out by means of the genetic algorithm combined with the finite element method. Moreover, we incorporate the circuit equations with the above methods. The results suggest that the magnetic stimulation with plural coils is effective for the pudendal nerve in the deep site. © 1998 IEEE.

This paper presents a novel design approach composed of two sequential processes for 3D magnetic shielding problems, which results in the global optimum solution in a shorter time. The feature of the proposed approach is the adoption of the specific boundary element with permeability of infinity. Assuming the permeability of infinity enables us to regard the thickness of ferromagnetic shields as infinitesimal, and thus to simplify the investigated model adequately in numerical analysis. This reduces the number of unknown variables and saves us a large amount of CPU-time for grasping the broad characteristics of the model. Some numerical results that demonstrate the validity of the proposed approach are also presented. © 1998 IEEE.

This paper describes a simple sensorless control scheme for permanent magnet synchronous motors based on the reduced order observer. By introducing the new control inputs, we realize both the decoupling and the linearization of the nonlinear electrical equations. This allows us to construct the reduced order observer for estimating the rotor speed and position. Owing to the linearization of the motor model, we can fix optimum gains of the observer under any operating condition. The validity of the proposed control scheme is confirmed by experiments as embedded code in a DSP - TMS320C32. The experimental results show high dynamic performance of the proposed control scheme.

In this paper we present a new approach to the sensor-less drive of permanent magnet synchronous motors based on the reduced order observer, First, we propose the new control inputs that decouple the d-axis current with the q-axis one. This enables us to construct the linear reduced order observer for estimating rotor speed and position. owing to the linearization of the motor model we can fix optimum gains of the observer under any operating condition. To confirm the validity of the proposed control scheme, experiments are carried out. The control is performed for the prototype of an eight-pole, 750W permanent magnet synchronous motor by using the software with DSP TMS320C31. The experimental results show high dynamic performance of the proposed control scheme.

In this paper we present a new approach to the sensor-less drive of permanent magnet synchronous motors based on the reduced order observer, First, we propose the new control inputs that decouple the d-axis current with the q-axis one. This enables us to construct the linear reduced order observer for estimating rotor speed and position. owing to the linearization of the motor model we can fix optimum gains of the observer under any operating condition. To confirm the validity of the proposed control scheme, experiments are carried out. The control is performed for the prototype of an eight-pole, 750W permanent magnet synchronous motor by using the software with DSP TMS320C31. The experimental results show high dynamic performance of the proposed control scheme.

In this paper we present a new approach to the sensor-less drive of permanent magnet synchronous motors based on the reduced order observer, First, we propose the new control inputs that decouple the d-axis current with the q-axis one. This enables us to construct the linear reduced order observer for estimating rotor speed and position. owing to the linearization of the motor model we can fix optimum gains of the observer under any operating condition. To confirm the validity of the proposed control scheme, experiments are carried out. The control is performed for the prototype of an eight-pole, 750W permanent magnet synchronous motor by using the software with DSP TMS320C31. The experimental results show high dynamic performance of the proposed control scheme.

This paper describes the method that makes it easy to simulate the magnetic levitation system by using the Boundary Element Method (BEM) or the hybrid Finite Element(FE)-Boundary Element(BE) Method. The proposed approach enables us to simulate a nonlinear control system in consideration of both the motion equation and the voltage equation. And the voltage equation contains the term of the leakage inductance that we have to consider in the actual model. © 1997 IEEE.

This paper describes a hybrid approach of the finite element method and the boundary type solutions, i.e. the Trefftz method and the boundary element method, for analyzing the magnetic field in rotating machines. This approach has the advantage of obtaining continuous physical quantities precisely without the singularities in calculating boundary integrals. Its application to a concrete model is also presented. © 1997 IEEE.

A novel approach to the three-dimensional optimal design of magnetic shields is presented, in which both shape optimization and topology optimization are achieved with the aid of numerical magnetic-field analysis. These numerical procedures are implemented by means of the hybrid finite element and boundary element method combined with the genetic algorithm. This results in an overall increase in the optimization speed with acceptable computational accuracy. Finally, some numerical results that demonstrate the validity of the proposed approach are presented. (C) 1997 American Institute of Physics.

This paper describes the method that makes it easy to simulate the magnetic levitation system by using the Boundary Element Method (BEM) or the hybrid Finite Element(FE)-Boundary Element(BE) Method. The proposed approach enables us to simulate a nonlinear control system in consideration of both the motion equation and the voltage equation. And the voltage equation contains the term of the leakage inductance that we have to consider in the actual model.

This paper describes a hybrid approach of the finite element method and the boundary type solutions, i.e. the Trefftz method and the boundary element method, for analyzing the magnetic field in rotating machines. This approach has the advantage of obtaining continuous physical quantities precisely without the singularities in calculating boundary integrals. Its application to a concrete model is also presented.

An analytical approach for calculating magnetic fields and potentials of massive current coils is presented. The proposed approach enables accurate, fast, and systematic evaluation of magnetic field intensity, vector potential, and scalar potential due to massive currents by means of simple and similar algorithms.

This paper describes the hybrid finite element (FE) and boundary element (BE) method for the eddy current problem including moving conductors. Electromagnetic phenomena due to the three-dimensional movement of conductors can be computed easily and naturally by the presented formulation. Its application to a simple model which has only one conductor is also given.

An analytical approach for calculating magnetic fields and potentials of massive current coils is presented. The proposed approach enables accurate, fast, and systematic evaluation of magnetic field intensity, vector potential, and scalar potential due to massive currents by means of simple and similar algorithms. © 1995 IEEE.

This paper describes the hybrid finite element (FE) and boundary element (BE) method for the eddy current problem including moving conductors. Electromagnetic phenomena due to the three-dimensional movement of conductors can be computed easily and naturally by the presented formulation. Its application to a simple model which has only one conductor is also given. © 1995 IEEE.

The finite element method (FEM) and the boundary element method (BEM) have entirely different characteristics. The FEM suits the analysis of a complicated region which includes nonlinear materials, and the BEM is useful for analyzing very large linear fields. This paper describes the hybrid finite and boundary element method which has the advantages of both methods. Here, we adopt the hybrid method to a 2D nonlinear magnetic problem with the moving boundary and make its advantages clear.

This paper proposes a smoothing method using the boundary element method(BEM) for the finite element(FE) analysis of the electromagnetic fields. This method has the advantage of obtaining the physical quantities continuously with good precision. This approach is also easily applied to a complicated region which could include non-linear materials or eddy currents. To verify this approach, the numerical results obtained by the proposed method are compared with the theoretical values.

This paper proposes a smoothing method using the boundary element method(BEM) for the finite element(FE) analysis of the electromagnetic fields. This method has the advantage of obtaining the physical quantities continuously with good precision. This approach is also easily applied to a complicated region which could include non-linear materials or eddy currents. To verify this approach, the numerical results obtained by the proposed method are compared with the theoretical values. © 1994 IEEE

The finite element method (FEM) and the boundary element method (BEM) are very useful for the numerical analysis of electromagnetic phenomena. Although the FEM suits the analysis of a complicated region which could include non-linear materials or eddy currents, the physical quantities such as the magnetic flux densities B are obtained discretely. Therefore we have to make fine meshes for accurate estimation of the electromagnetic force by the Maxwell stress method. On the other hand the BEM makes it possible to derive continuous physical quantities at inner points by using analytical expressions, not by relying numerical derivation as in case of the FEM. In this paper we first use the FEM for analyzing the electromagnetic fields of the concrete model in terms of the magnetic vector potential A and the electric scalar potental φ. Next we locate the temporary boundary enclosing the region where we desire the values of B, and apply the BEM (using the H method or the φ method) to this region in order to obtain B continuously. Then we can calculate the electromagnetic force accurately by the Maxwell stress method. To verify this approach, the numerical results obtained by the proposed method are compared with the theoretical values. © 1994, The Institute of Electrical Engineers of Japan. All rights reserved.

As the analysis methods of the electromagnetic field, the finite element method (FEM) and the boundary element method (BEM) are well-known. In this paper, we propose the following method. Firstly, we analyze the investigated region only by the FEM, after that locate the hypothetical boundary properly surrounding the points where we desire the values of B in the homogeneous region. Finally, we calculate B at inner points by the BEM with the values by the FEM as the boundary conditions. Analyzing by the FEM at first, this method is easily applied to the complicated multi-material problems. We adopt several kinds of physical quantities to this method as unknowns, and also show the propriety and advantage of this method by analyzing the simple model.

The finite element method (FEM) and the boundary element method (BEM) have entirely different characteristics. The FEM suits the analysis of a complicated region which includes nonlinear materials, and the BEM is useful for analyzing very large linear fields. This paper describes the hybrid finite and boundary element method which has the advantages of both methods. Here, we adopt the hybrid method to a 2D nonlinear magnetic problem with the moving boundary and make its advantages clear. © 1994 IEEE

There are several ways to define the gauge condition in the A - phi method for the 3-D eddy current analysis: e.g. the Coulomb gauge, the Lorentz gauge, etc. Unlike the Coulomb gauge, the physical meaning of the potentials in the Lorentz gauge is not obvious. Therefore this paper introduces a novel physical meaning of the Lorentz gauge, and describes the relationship between these gauge conditions in the A - phi method systematically from a physical viewpoint.

This paper presents the hybrid finite element and boundary element method using edge elements for a 3-D electromagnetic problem with open boundary. In this method we adopt the modified magnetic vector potential A* and the magnetic field intensity H as the physical quantities. The appropriate boundary element discretization described in this paper makes it easy to couple the BE region with the FE region through the transformation of unknown variables.
To verify this approach some numerical results obtained by the proposed method are compared with measured ones.

This paper presents the hybrid finite element and boundary element method using edge elements for a 3-D electromagnetic problem with open boundary. In this method we adopt the modified magnetic vector potential A* and the magnetic field intensity H as the physical quantities. The appropriate boundary element discretization described in this paper makes it easy to couple the BE region with the FE region through the transformation of unknown variables. To verify this approach some numerical results obtained by the proposed method are compared with measured ones. © 1993 IEEE

There are several ways to define the gauge condition in the A-ϕ method for the 3-D eddy current analysis: e.g. the Coulomb gauge, the Lorentz gauge, etc. Unlike the Coulomb gauge, the physical meaning of the potentials in the Lorentz gauge is not obvious. Therefore this paper introduces a novel physical meaning of the Lorentz gauge, and describes the relationship between these gauge conditions in the A - ϕ method systematically from a physical view-point. © 1993 IEEE

This paper deals with a boundary element method using edge elements for 3-D eddy current problems. In this method the eddy current region is formulated only by means of the electric field intensity E, while the free space only by the magnetic field intensity H. In each region, both unknown variables are independently expressed from each other. By both physical consideration and the appropriate boundary element discretization, these physical quantities can be connected on the interface with ease. To verify this approach some numerical results obtained by the proposed method are compared with measured ones. © 1993 IEEE

This paper describes the hybrid finite element and boundary element method for the electromagnetic problems. To attain good accuracy, we adopt the magnetic field intensity H as much as possible as the physical quantity in the hybrid method. We also propose a new boundary element discretization in the H formulation, which makes it easy to couple the BE region with the FE region by introducing the edge boundary element.
Some numerical results obtained by the proposed method are compared with measured ones.

This paper proposes a novel boundary element formulation using the scalar potential in the hybrid finite element (FE) and boundary element (BE) method for the electromagnetic problems. We adopt the analytical integration as much as possible in this method. This approach has the advantage of reducing the number of unknown variables and makes it easy to couple the BE region with the FE region. Some numerical results obtained by the proposed method are compared with measured ones.

The linear induction motor (LIM) is structurally divided into the flat and the tubular-type. In this paper, we study one kind of tubular linear induction motor which has the primary configuration composed of four pieces of flat-type core. We call this type of motor "the square tubular LIM". The tubular LIM has such a feature that its primary winding is a kind of ring winding, so we can independently supply the primary currents in each slot and hence easily obtain the various winding schemes. Though the square tubular LIM has various merits as stated above, the number of slots is usually limited in conventional applications. In this paper, therefore, we investigate the exciting current scheme with a view to improving primary magneto-motive forces. Firstly we determine the exciting current scheme in unloaded system by using polyphase alternating currents. Secondly we determine another exciting current scheme in loaded system by the hybrid finite element and boundary element method, and the augmented Lagrange multiplier method. Finally we confirm the proposed method by experiment. © 1992, The Institute of Electrical Engineers of Japan. All rights reserved.

This peper describes the hybrid finite element and boundary element method for the electromagnetic problems. To attain good accuracy, we adopt the magnetic field intensity H as much as possible as the physical quantity in the hybrid method. We also propose a new boundary element discretization in the H formulation which makes it easy to couple the BE region with the FE region by introducing the edge boundary element. Some numerical results obtained by the proposed. method are compared with measured ones. © 1992 IEEE

This paper proposes a novel boundary element formulation using the scalar potential in the hybrid finite element (FE) and boundary element (BE) method for the electromagnetic problems. We adopt the analytical integration as much as possible in this method. This approach has the advantage of reducing the number of unknown variables and makes it easy to couple the BE region with the FE region. Some numerical results obtained by the proposed method are compared with measured ones. © 1992 IEEE