Hiroshi Mochikawa

A voltage ratio-based efficiency control method for 3 kW wireless power transmission

This paper presents a novel control method for wireless power transmission (WPT). The proposed method can maximize the power efficiency only by controlling the voltage ratio between the primary and the secondary side. Experimental measurement results of the prototype system with 3 kW power transmission show the efficiency difference between the proposed control method and the available maximum value is less than 0.3 % even with a large variation of coil-to-coil distance and load voltage. The automatic controller for the proposed method provides the load-following operation, maintaining both constant power and high efficiency, using a WLAN connection.

EMI prediction method for SiC inverter by the modeling of structure and the accurate model of power device

In recent years, the switching speed is increased accelerately. And, the increase of EMI by high dv/dt is a problem. In this paper, the Tri-phase 400 Vrms inverter for system interconnections which used SiC-JFET is analyzed. And, it is shown that noise terminal voltage is analyzable with an error of ±15 dB by highly precise modeling.

System fault test of SiC device applied 6.6kV transformerless D-STATCOM

This paper reports the investigation results for transformerless Distribution-Static Synchronous Compensator (D-STATCOM) with Modular Multilevel Converter (MMC) topology. The D-STATCOM has cascaded Silicon-Insulated Gate Bipolar Transistor (Si-IGBT) inverter cells and Silicon Carbide-Junction Field Effect Transistor (SiC-JFET) inverter cells. SiC-JFET inverter cells are operated with Pulse Width Modulation (PWM) since the low switching losses. The Si-IGBT inverter cells have higher DC voltage than the SiC-JFET inverter cells, and they are operated with one-pulse operation that output one positive and one negative pulses during a cycle. MMC topology and high voltage Si-IGBT inverter cells realized connecting the D-STATCOM to 6.6 kV distribution system without transformer. A prototype model of the D-STATCOM rated at 6.6 kV, 100 kVA was built and its field test was executed. The experimental results prove the stable rated operation and Fault-Ride-Through performance.

A Transformerless 6.6-kV STATCOM Based on a Hybrid Cascade Multilevel Converter Using SiC Devices

We have developed a full-scale prototype of transformerless static synchronous compensator (STATCOM), rated at 6.6 kV and 100 kVA, based on a hybrid cascade multilevel converter using SiC devices. The topology employs multivoltage converter cells, Si and SiC semiconductor devices, and hybrid modulations in the converters. One phase of the STATCOM has two Si insulated-gate bipolar transistor converter cells and two SiC-JFET converter cells connected in series. The SiC cells are operated with high-frequency pulse width modulation. The Si cells carry higher dc voltage, resulting in smaller converter volume by reducing the number of cascaded cells. To minimize the loss, the Si cells are operated with one-pulse. The balance control of dc voltage of the hybrid cells is also discussed. We tested the developed STATCOM in a full-scale 6.6-kV distribution grid. The experimental results show a stable rated operation and fault-ride-through performances. Moreover, we analyzed its loss and volume and discussed them based on the developed STATCOM. The estimated loss was approximately 0.3% at rated power, which is comparable to an all-SiC configuration. It also has an advantage in its small volume compared with other configurations. These analyses revealed that the hybrid configuration is a suitable topology for low-loss and small-size distribution STATCOM.

A proposal for a single stage isolated AC-DC converter with zero voltage switching

In this paper, we propose new isolated AC-DC converters which have only one conversion stage; in addition it can operate zero voltage switching in all switching devices. Moreover, we propose control strategy for these converters, and also confirmed it by experimentation or simulation using 100W prototype.