This study proposes a control method for a dual active bridge (DAB) converter for battery systems to improve loss of light load. The proposed method reduces the circuit gain nonlinearity caused by phase shift control focused on the transformer losses. Therefore, based on calculations through the model of the proposed method and experimental results from load switching, the proposed method is shown to have lower light load loss and better controllability than conventional methods.

This paper presents a circuit analysis model to predict spike surges at mechanical contacts of a DC brush motor. Measured spike surge waveforms are classified into four types depending on the existence of a steady arc and a showering arc. The directly open without arcs condition is clarified to be the maximum spike surge voltage condition. Additionally, an equivalent circuit model is developed to simulate spike surges. This model considers complex high-frequency characteristics and rotation angle dependence of impedances. A full-slot equivalent circuit model is represented by a combination of single-slot models. The spike surge simulation model considers induced voltage and variable resistors representing mechanical contact switching in addition to impedance characteristics. The simulated spike surges show good quantitative agreement with the measured values.

The isolated class-Φ₂ DC-DC converter has attracted attention as a circuit topology that achieves high efficiency. However, there are no reported analysis methods and design techniques for isolated class-Φ₂ DC-DC converters. In this study, the harmonic analysis technique is applied to the isolated class-Φ₂ DC-DC converter, which enables circuit analysis with arbitrary duty ratio. In addition, design curves are obtained using this harmonic analysis, and design examples are presented. The loss analysis of the manufactured isolated class-Φ₂ DC-DC converter was performed to clarify the ratio of copper losses generated by the magnetic components.

This paper proposes a multi-port DC-AC converter with high efficiency and high-power density. The proposed circuit consists of a full bridge converter, a series active filter, and an unfolder circuit. The proposed circuit reduces the low switching losses owing to the square waveform operation with low switching frequency. In addition, the proposed converter improves the power density because the number of inductors is significantly reduced compared to the conventional multi-port converter. As the experimental result, the maximum efficiency of the proposed circuit reached 99.3%. Finally, the power density of the proposed converter is evaluated by the Pareto front curve. As the result, the power density of the proposed circuit was increased by 1.6 times in comparison with the conventional circuit.

This paper proposes a low vibration stopping method by switching between the free-run and short-circuit braking modes of a compressor. Vibrations are generated by the bouncing of the rotor caused by load torque fluctuations. The proposed method suppresses the bouncing by stopping the motor during the suction process, thereby preventing the generation of a large torque. In order to stop the motor during the suction process, the proposed method switches from the free-run to short-circuit braking mode at the top dead center, which is the starting point of the suction process. Furthermore, the inrush current during the short-circuit braking mode is suppressed using a hysteresis current controller. The vibrations are evaluated under four pressure conditions using the conventional and proposed methods. The results show that, the proposed method achieves more than 50% reduction in the amplitudes of the vibrations at all four pressure conditions. Notably, the proposed method reduces the amplitude of the vibration by 71% under the high-pressure condition.

A diode-clamped linear amplifier (DCLA) is proposed to realize low electromagnetic interference (EMI) caused by switching operations. A new concept of the DCLA, namely the higher efficiency unequally divided voltage power supply DCLA (DCLA-UeDV), is proposed. In previous studies, the optimal voltage ratio was derived, and a 1.7 percentage points improvement in efficiency was realized for a rated unity power factor load. However, it has not been examined whether the conversion efficiency can be improved, except during the rated operation. In this study, operation of the DCLA is analyzed for changes in the amplitude of the output voltage and load power factor. Then, the advantageous operating region of the DCLA-UeDV against DCLA-eDV is clarified.

The high-thrust linear motor with a lightweight and high-strength mover was developed for operating circuit breakers. The linear motor is composed of a lightweight mover that has permanent magnets sandwiched between magnetic poles and an armature with a three-dimensional magnetic circuit. The specifications and performance of the linear motor were determined to cut off current soundly. Then, a prototype of a fully electrically operated breaker using linear motor was investigated. The linear-motor-based operating mechanism designed for the circuit breaker reached the open-pole position in 13.2ms from the start of movement. However, the time from opening to 0.5 cycle was 9.0ms. In addition, the variation in breaking operation time was within 1ms, which was expected that stable controlled operation.

A high-voltage DC feeding system, which consists of higher-voltage feeders and DC-DC converters in addition to the existing feeding circuit, can be used to supply vehicles power with a conventional feeding voltage. In this system, it is important to consider the control method of the converter to maximize the energy savings. Here, we propose a converter control method to make the voltage ratio between the overhead contact line and the higher-voltage feeder constant and named the DC-AT control method. Furthermore, we devised a load sharing control that reduces cases where a specific converter momentarily becomes a high load, by sharing the power transfer between multiple converters, and reduced the rated power of the converter. In addition, we confirmed the effectiveness of the proposed control method via simulations, demonstrating that excellent energy savings by promoting the interchange of regenerative power and the suppression of the high load of the converter could be achieved simultaneously.

The resistance torques around the ankle joint differ between plantar flexion and dorsiflexion during passive movements at the same angle. Some conventional methods that have modeled the relationships between the joint angles and resistance torques using time-invariant elastic coefficients, which cannot account for the hysteresis property. Here, we propose a new modeling method using a time-varying elastic coefficient to represent the hysteresis of the ankle joint. In the present study, we used a custom-made motorized device to rotate the ankle joint passively and measured the joint angles and resistance torques from five healthy participants. By comparing the measured torques with the estimated values, we show that the proposed method can estimate the torque with less error than the conventional methods.

This paper presents an induction heating system using a matrix converter. The proposed circuit consists of a three-phase AC to high-frequency single-phase AC converter, two high-frequency transformers, and a heating coil. Because the power conversion number of the proposed system is one and SiC MOSFETs are used for switching, a downsized and highly efficient system is achieved. In an induction heating device, it is inevitable that the heating coil be replaced according to the heating object. However, this specification causes power supply current distortion. By controlling the matrix converter, both the downsizing and high efficiency of the system, as well as the specifications of the heating device are realized. Therefore, in this study, the authors propose a circuit configuration and its control method at the rated output frequency or less for an induction heating system using a matrix converter. In addition, the authors propose the derivation method of the duty cycle to suppress the source current harmonics. The effectiveness of the proposed system is verified by experiments.

This paper proposes a method for suppressing the fundamental and 6th-order oscillations in the estimated position of the position sensorless control of concentrated winding permanent magnet synchronous motors (PMSMs) with all-pass filters. In general, the DC offset in the current or voltage sensor causes the fundamental oscillation in the estimated position. In addition, the 6th-order oscillation in the estimated position is emphasized partically for the stator winding with the concentrated structure for PMSMs. To address these issues, this paper proposes the reduction of these oscillations with the assistance of the flucuation of the estimated flux amplitude and its delayed utilization. Finally, some experimental results show the feasibility and effectiveness of the proposed method.

This paper proposes a new and general construction method for orthogonal matrices used in orthogonal transformations that allow the decomposition and independent control of the fundamental and harmonic components with the phase sequences contained in multiphase signals of multiphase AC motors.