This study proposes a capacitive wireless power transfer system using immittance converters. In this system, two immittance converters were set in the front and back stages of the coupler, enabling the suppression of the effects of lateral misalignment. Four kinds of immittance converters were integrated into the system in numerical analysis and were compared with one another. Additionally, Monte Carlo Tree Search was used to miniaturize the system while maintaining efficiency. The experiments employing optimized system confirmed that the system can perform with high efficiency even at significant misalignments.

It is important to drive an IPM motor system stably. However, unstable oscillation at the DC input has been reported. According to the impedance method, the stability is assured when the input admittance of the drive system is passive or resistive. In this paper, we propose a passive admittance control method utilizing a Lyapunov-based method. The control principle is first described and then a design example is detailed. It is shown that the proposed method achieves passive frequency characteristics for the input admittance. Its stable operation behaviors were investigated both by simulation and experimentally.

Inductors used in power converter circuits are subjected to various currents when rectangular voltage waveforms are applied. Under these conditions, instead of forming a hysteresis loop, the magnetic material in the inductor forms minor loops on the BH plane corresponding to the current flow. The area of these minor loops represents the iron loss per unit volume. The shape and area of the minor loops vary depending on the values of the rectangular voltage waveform and DC current, as well as the position of the loop on the BH plane. This paper proposes a measurement procedure to accurately measure and analyze the position and shape of minor loops by controlling the current flowing through the inductor in a half-bridge inverter.

This paper presents a PWM control method for three-phase to single-phase matrix converters based on the fundamental component of the high-frequency output voltage. Power converters used in resonant circuit configurations, such as wireless power transfer systems, are required to output the high-frequency AC voltage with the desired fundamental component. A matrix converter can output the high-frequency AC from the commercial AC in a single power conversion stage. Although the input three-phase AC voltage of a three-phase to single-phase matrix converter takes non-constant values, the authors propose a control method that always outputs the high-frequency AC voltage with the desired fundamental component. Real-time control is enabled by making the complicated theoretical equations simple. Furthermore, the control method is standardized to be independent of the input and output voltage values, current values, and frequencies. The usefulness of the proposed control method is experimentally verified.

This paper proposes a novel permanent-magnet synchronous motor (PMSM) mathematical model based on the premise that only armature reaction flux causes iron loss. It insists that the total loss in the case of zero torque is minimized by only zero stator current, which is consistent with experiences of engineers. The model consists of three basic equations that are self-consistent with others, and consequently have no mathematical contradiction. In addition to the model, this paper proposes a PMSM vector simulator based on the model. Moreover, the vector simulator is validated by numerical experiments.

This paper studies electromagnetic interference (EMI) noise mitigation for large-current SiC power modules with integrated DC-link capacitors. Symmetrically-placed DC-link capacitors in a power module most effectively reduce conducted-EMI in the MHz-band. The challenge is to reduce the several hundred kHz band differential-mode noises caused by the parallel connection of the smoothing- and DC-link capacitors.

This paper proposes a new generalized zero-phase-correction method for the linear signal comparison PWM. The proposed method has the following features: (a) It is simple. (b) By using the method, it can easily generate various switching signals similar to the conventional space vector PWM. (c) It can also generate switching signals similar to a random space vector PWM.

This article introduces Power Electronics research group at National Institute of Technology, Yonago College. Our research focuses on the power electronics circuits, rotating machines, and renewable energy.