This paper proposes an extended method of zero-voltage switching (ZVS) range for a dual active bridge (DAB) matrix converter with a discontinuous current mode (DCM). In the traditional DAB converter, ZVS cannot be achieved at a light load condition. The duty ratio calculation to achieve power factor correction and ZVS is explained using a circulating current. From the experimental results using a 5-kW prototype, the ZVS operation with zero transmission power is achieved by increasing the circulating current. In addition, the grid current distortion is lower than 5.0% at the rated power regardless of the DC voltage variation of plus or minus 20%.

This paper proposes a local path planning method considering blind spots based on the cost map for a wheeled mobile robot. In this research, a laser range finder (LRF) is utilized to recognize environmental information in real time. Blind spots occur when corners or obstacles are present in the environment. If humans or objects move from the blind spots toward the robot, collisions might occur. To avoid this collision, this paper describes the path planning that takes into account the blind spots. The position of a human in the blind spots is estimated from environment information measured by LRF. It is assumed that a human can move in all directions from these estimated positions. Therefore, in the cost map, the cost of the estimated positions of the human is represented as a circle. This cost is used for the calculation of path planning by dynamic window approach. Using the proposed method, the path plan of the robot is achieved by considering its blind spots. The effectiveness of the proposed method is further demonstrated through simulations and experiments.

For the switched reluctance motor (SRM), it is difficult to derive optimum control parameters to suppress vibration and noise. In previous studies, to suppress the torque ripple, which is one of the causes of vibration, it was necessary to derive control parameters by trial and error, for example, by using finite element analysis. Thus, vector control specialized for the SRM has been proposed to simplify the construction of the control system. This paper proposes torque ripple suppression control of the vector-controlled SRM. In the proposed control method, the torque ripple is suppressed by feeding back the estimated torque to the reference torque by considering its harmonic components; the torque ripple can then be suppressed with a simple controller configuration. It was experimentally observed that the sixth harmonic component of the torque is suppressed by a maximum of 74.0% compared with that obtained in the conventional control method.

An N-phase interleaved converter was analyzed here to improve the current control performance of a welding power supply. Consequently, it was found that the collective current control method of the N-phase interleaved circuit has a current control response closing to that of a single-phase converter circuit with N times carrier frequency and 1/N output inductance. This method reduces the accumulated energy of inductance to 1/N and lowers the heat generation of the device, which can contribute to the miniaturization and higher performance of the welding power supply.

Many techniques have been proposed as power supply methods for high-side gate drivers. However, most techniques that do not depend on the topology of the main circuit have drawbacks related to the size and cost. This paper proposes a novel floating power supply based on capacitive isolation. The proposed circuit is designed to operate independently of the main circuit, and it is cheaper and smaller than conventional circuits. The proposed method is applied to a diode-clamped multilevel topology and is validated by experiments.

In this study, we examined a closed type linear motor with a continuous thrust of 10kN. First, the loss at the rated operation was calculated through a magnetic field analysis, and the dominant loss component was clarified. When the application was small with a low speed and large thrust, copper loss was dominant. Next, a heat transfer analysis was conducted by using a heat conductor that avoids the magnetic path, to confirm the structure that can reduce the winding temperature. The result shows that the winding temperature can be reduced under the target temperature (150°C) by placing the heat conductive material where the formation of an eddy current is difficult.

Short cruise range is a major issues in electric vehicles, and dynamic wireless power transfer has been proposed to solve this problem. In this study, a new dynamic power transfer system is introduced, called the hird generation wireless in-wheel motor, that integrates the drive circuit and motor. Additionally, a methodology of the transmitter and receiver coil design that can calculate inductance and resistance of the rectangular spiral coils in a fast manner is proposed. It considers the theoretical efficiency of coils, current of coils, and voltage of resonance capacitor as constraints. Inductance calculation models only use coordinates of coil edge and the distance between coil and ferrite core. The coils designed by the proposed method were manufactured and evaluated using an LCR meter. The calculation error of the self-inductance and mutual inductance was found to be ±9%. With the transmitter coil and receiver coil, an output and DC to DC efficiency of is 18kW and 95.2%, respectively, were obtained by actual wireless power transfer test.

High voltage (HV) DC power suppliers are widely studied to improve the efficiency and reduce the size. Cockcroft-Walton (CW) voltage multiplier is generally used in conventional HV power supply owing to its high step-up ratio, low voltage stress on components, and compactness. HV DC power supply can be miniaturized by driving the system at high frequency (HF). In this study, an HV SiC schottky barrier diode (SBD) module was developed for HF HV CW circuits, which consist of multiple SiC SBDs directly connected in series and molded in a module package. The switching behavior of the developed SiC SBD module is discussed from the viewpoint of voltage distribution among SBDs.

This paper proposes series compensation circuit for traction energy storage systems. The proposed circuit has three advantages: high efficiency, downsizing, and low weight because the circuit converts only a part of the power. Four-mode operation of the proposed circuit was confirmed by simulation. The traction energy storage system, which is composed of the proposed circuit, battery, and high-speed circuit breaker, has strong characteristic for short circuit of feeder system by fitting of short circuit test and simulation. In the field test, it is evaluated to operate as a peak-cut and emergency power supply source using the traction energy storage system.

Dual active bridge (DAB) converters suffer from DC-bias caused due to the phase-shift control. This paper proposes a novel DC-bias suppression method that has a fast transient response and is easy to implement. In this method, the transient state can be completely removed by considering the phase of the inductor current. The validity of the proposed method was verified through a simulation.

This research group focuses on the application of power electronics and motor drive to the traction and industrial systems.