This paper proposes a hybrid modulation for a solid-state transformer (SST) with an input-series output-parallel (ISOP) connected cells. One of the cells on the high-voltage side for power factor correction (PFC) is driven using pulse width modulation (PWM) to compensate for the harmonic components of the input current, whereas the other cells are driven using square-wave operation. The square-wave operation cell enables the use of low-cost Si devices instead of expensive SiC devices, which reduces the cost of the SST. Moreover, this paper proposes the balancing control of the conduction loss in each square-wave cell. The experimental results demonstrate that the total harmonic distortion of the input current is 2.91%, and the conduction loss of each square-wave cell is well-balanced.

Permanent magnet synchronous motors (PMSM) are very popular in the industrial market. Recently, robots are installed to compensate for the shortage of labor. Due to the increase in motors, the number of power lines and position sensor cable wiring are increased; this increase in complicated wiring is a problem. As a method to solve these problems, power superimposition technology in the power line of a PMSM is expected to reduce the distribution cables. In this paper, the power superposition technology method, and circuit equations of mounting transformers in power lines are presented and are then verified by experiment, simulation, and linear analysis. The circuit equation is proposed as a three-phase circuit equation, which is transformed into a dq-circuit equation by a transformation matrix. The characteristics of the electric angular frequency versus the dq-axis voltage demonstrated satisfactory results, with errors within 1% in linear analysis and simulation. The linear analysis and experiment are shown to be similar, although there are some errors. The validity of the circuit equations could be demonstrated by the verification results.

A novel voltage boost system using DC-inputs direct electric-power converter (D-EPC) is proposed. D-EPC is an inverter that can control the distribution of power from two sources. In this study, a voltage boost system without boost chopper was developed using the power distribution control of D-EPC. The power distribution control can control the voltage of the smoothing capacitor in the D-EPC. The effectiveness of the proposed voltage boost system was verified using a prototype of the D-EPC circuit and controller.

This paper discusses a compressor drive system for a room air conditioner. The system uses a single shunt current detection and a position sensor-less vector control technique. In addition, a new adaptive flux observer that considers the fluctuation in current detection timing is also proposed. The proposed observer improves the accuracy of speed estimation in a high-speed rotational condition. The room air conditioner, including this compressor drive system, has been mass-produced in our company.

This paper proposes a zero-voltage switching (ZVS) scheme for a dual active bridge (DAB) converter in the full load range. The switching state of the DAB converter with a phase-shift control becomes a hard switching state under an input and output voltage imbalance or light load. Thus, the proposed method regulates the phase-shift angle, output voltage angle of full-bridge circuits, and switching frequency to achieve ZVS for the DAB converter. The DAB converter implementing the proposed ZVS scheme is applied to vehicle-to-home (V2H) systems. Experimental results reveal that a V2H unit using the DAB converter achieves an efficiency 97.2% with the proposed ZVS scheme.

In this study, the authors experimentally verify the AC-side inductor loss of the three-phase voltage-fed inverter by evaluating the core temperature. Two-phase pulse width modulation (PWM) is renowned for its low switching losses. However, the harmonics of the AC-side voltages and currents generated by a two-phase PWM are greater than those of a three-phase PWM. Therefore, the increase in power loss due to the harmonics in the inductor connected to the AC side of the inverter is concerning. To address this issue, the authors experimentally verify and evaluate the AC-side waveforms, total harmonic distortion (THD), power dissipation and inductor core temperature, and conversion efficiency for the three-phase voltage-fed inverters with the different PWM schemes. The results demonstrate that the two-phase PWM improves conversion efficiency compared to the three-phase PWM, assuming the same THD as for the three-phase PWM. Additionally, the two-phase PWM reduces the THD compared to the three-phase PWM and reduces the power dissipation and core temperature of the inductor to the same extent as the three-phase PWM method, assuming identical conversion efficiency.

Recently, vibration generators have attracted considerable attention. Generally, vibrations include not only the fundamental frequency but also any harmonics. We proposed an internal capacitor cancel control (ICCC) rectifier to improve the output power. The proposed rectifier nullifies the internal capacitor to improve and maximize the output power. Using numerical methods, our previous paper theoretically revealed that the proposed rectifier for the vibration generator improved the output power. This study experimentally analyzes the improvement of the output power from vibration generator by using the proposed rectifier for vibrations, including the third harmonics.

Increased penetration of photovoltaics may result in voltage violations in distribution power system. Reactive power is one method for measuring voltage violations in distribution lines. In this study, to reduce additional installation cost of reactive power control equipment, reactive power control using air conditioners with a built-in active filter was developed. The compatibility of harmonic suppression and line voltage controls of reactive power control using air conditioners with built-in active filters was experimentally confirmed.

Mizukoshi laboratory specializes in the field of power electronics and motor drive systems, with a particular focus on advancing dual inverter fed open-end winding motor drive technology. This document provides an overview of our laboratory's research and activities.