In the Shinkansen system, the voltage drop caused by the train load is compensated by ground equipment such as Static Var Compensator (SVC) in the conventional method. However, a previous study proposed a method of compensation by the trains that consume reactive power, in addition to the ground equipment. By applying this method, it is possible to improve the compensation compared with when the feeder voltage is compensated only by the ground equipment. Then, the capacity of the ground equipment can be reduced under the same train load condition. However, it is necessary to decide the capacity of the ground equipment by considering the compensation of both the trains and the ground equipment. This article conducts a quantitative study on the effect of onboard reactive power compensation on the reduction of the ground equipment capacity. As a result, the capacity of ground equipment can be reduced up to approximately 83% of the conventional capacity.

A multiphase DC-DC converter consisting of a coupled inductor and fast switching devices enables power electronics equipment to achieve a high power density. However, with such devices, the fast voltage transition generates substantial common mode (CM) noise. However, there are very few studies on CM noise reduction for multiphase converters using a coupled inductor. Therefore, in this paper, a CM noise reduction method is proposed for a multiphase DC-DC converter that hardly lowers the power density.

Herein, the loss reduction of a motor drive system is experimentally studied by means of the 5th harmonic superimposition in the reference signal of a sinusoidal PWM inverter from the perspective of nonlinear magnetic characteristics. The measured data of the motor drive system loss exhibits a reduction of 1.5% in the condition when the superimposition rate is -0.15. More specifically, the motor core, copper and inverter losses are reduced. The results confirm the feasibility and efficacy of the proposed method. According to the fundamental research of a ring test with the same electrical steel as the motor, the magnetic characteristics of the B-H curve changes in the case of the 5th harmonic superimposition, which decreases the fundamental component of the current. Accordingly, the loss is considered to be reduced due to the decline in the fundamental current component and carrier frequency components.

This paper presents a bidirectional non-isolated dc-dc converter based on three-level flying-capacitor converters. The converter uses multiple auxiliary converters, each of which is based on cascaded chopper cells and an inductor, which enables active control of the inductor current. This paper compares the following two current control methods: conventional sinusoidal-wave current control method and proposed trapezoidal-wave current control method, in terms of ac-current peak values, dc-current values, current root-mean-square (RMS) values, voltage ripples in dc-capacitor voltages, current ripples in dc currents, and converter efficiency. The validity of the comparison and trapezoidal-wave current control method is verified in a simulation using MATLAB and experimentally using a 2-kW downscaled model.

This paper proposes a losses-analysis model of a DC-output converter based on the approximated equations from measurements and a datasheet. Target verification circuit consists of a DC-voltage source, a smooth capacitor, two half bridge legs, and a load inductor connected to the midpoints of the half bridge legs, which controls the continuous average DC current of the load inductor. A use of self-measured data, compared with the use of datasheet values, enables expanding the ranges of the considerable target parameters. Hence, lesser order approximated equations can deal with more target parameters with less calculation period than that in a conventional time domain simulation. In this study, calculation flow of losses from losses of power devices and an inductor to circuit losses was developed. Subsequently, a semiconductor losses model and inductor losses model were developed via the linear least square method. Finally, a 400V experimental system was developed to verify the accuracy of the circuit losses at 16 specified operating conditions by varying three verification parameters, switching frequency, gate resistance, and inductance. The result shows that the losses calculated using the proposed model has good accuracy with an error of 1.9% to 10.6% to the measured result.

This paper proposes a magnetic equivalent circuit model for an interior permanent magnet synchronous motor (IPMSM) for the optimal design of the entire system. The computational speed of the proposed model is greater than that of the finite element method (FEM), and the model is suitable for large scale optimization problems. Unlike conventional magnetic circuit models, the proposed model can reflect the dq-axis saliency, which enables analysis under operating conditions using the reluctance torque, which is essential in IPMSMs. In the proposed model, rotor rotation is represented by an AC magnetomotive source, and the saliency characteristics are represented by a multi-phase-q-axis transducer that simulates a q-axis magnetic path connected in parallel to the magnets. The effectiveness of the proposed method is verified by comparisons with the FEM, and the results reveal good agreement under several conditions. Furthermore, the computation of the N-T characteristics and efficiency maps is verified, and consequently, the proposed method is deemed capable of obtaining these maps with sufficient accuracy for the initial design, and the required computation time is four orders of magnitude lower.

This paper presents a theoretical discussion on a combined-compensation control method and its stability on harmonic resonance for grid-connected converters. The interaction between the grid impedance and the grid-connected converter potentially creates harmonic resonance. The compensation control with a combination of a digital filter and a virtual impedance is an effective solution for this problem. The theoretical analysis developed in this study reveals that the proper use of the two control schemes enhances the availability of grid-connected converters. Simulated results obtained from a three-phase high-power converter system verify this analysis.

This study aims to verify the application of amorphous metals to high-speed drive motors. We propose a new high-speed motor that applies amorphous metal to ultra-high-speed motors used in home appliances. The proposed motor can reduce both the iron loss and copper loss compared to conventional vacuum cleaner motors. We performed characteristic analysis and prototype evaluation through magnetic field analysis of the proposed motor. The analysis results at the same operating point, confirm that the efficiency improvement effect was approximately 1% compared to the highest grade electrorical steel sheet machine. The prototype evaluation results of the new high-speed motor, confirm that various characteristics obtained by the analysis could be reproduced. As a result of evaluating prototypes composed of different materials, the effect of improving motor efficiency by applying amorphous metal is confirmed quantitatively.

A high Bs nanocrystal alloy has been used for the teeth portion of the stator core of distributed winding IPM motors to improve their efficiency by expanding the area. In an amorphous metal, the efficiency decreases in the high torque region therefore the aim is to improve the efficiency. Accordingly, analysis studies and prototype evaluations were conducted to quantitatively understand the effect of improving the efficiency. Based on the results of the analysis, the effect of the magnetic properties of the high Bs nanocrystal alloy on the torque characteristics of the motor and the effect on the iron loss is clarified. The results reveal that the prototype motor for verification can improve the efficiency in all operating areas compared to the electrical steel sheet machine.

By applying an unregulated LLC resonant converter to a multi-input modular DC-DC converter (MIMC), the LLC converter can be operated at an optimal frequency while achieving power source flexibility. However, the output characteristics of an LLC converter are easily affected by the resonance parameter, and when connected in parallel, the output current is unbalanced. In this paper, we propose a current sharing control method to solve the current imbalance problem, and automatically balance the output current of each module. The effectiveness of the proposed current sharing control method is verified by simulations and experiments.

This paper proposes two new generalized orthogonal matrices that can be used for orthogonal transformation in six-phase motors with double independent three-phase windings. The transformation that is also called VSD is essential for the control of six-phase currents contaminated by harmonics and/or high-speed mode component. Most importantly, the proposed generalized orthogonal matrices have the potential to enable new development in the current control of six-phase motors.