Hiroaki Miyata

Harmonic current reduction control for grid-connected PV generation systems

Integration of renewable energy sources (RES) with significant capacity, including photovoltaic (PV) generation systems, into the grid is expected within ten years. Such RESs bring to the grid not only their benefits but also some technical problems, as increase of harmonic currents. Compliance with the technical requirements for harmonic current is necessary for successful increase of RES capacity. A scheme to reduce harmonic current for grid-connected PV generation systems was developed. This control scheme effectively reduced harmonic current in the grid current of the PV generation system caused by voltage distortions at the grid. Experiments using a prototype of the power conditioning system (PCS) showed its validity. 400-kW PCSs with the control scheme have been installed and have been in service since the end of 2009.

Five-year's verification test results in Hokuto mega-solar system

The New Energy and Industrial Technology Development Organization (NEDO) advertised for consignment research business called “Verification of Grid Stabilization with Large-scale Photovoltaic Power Generation Systems” in 2006. Two sites were selected for the verification tests, which were Hokuto City in Yamanashi Prefecture and Wakkanai City in Hokkaido. Mega-solar system (Large-scale photovoltaic system) of about 2MW and about 5MW was constructed each. Five-years verification test results of grid stabilization and PV characteristics evaluation in Hokuto mega-solar system are discussed in this paper.

Verification test of grid stabilization and evaluation of PV module characteristics for large-scale PV generation system

About 2MW PV system was constructed in Hokuto city of Yamanashi Prefecture in Japan for verifying grid-stabilization control methods and evaluation of various kinds of PV module characteristics for construction of future large-scale PV systems. Five-year tests were finished in March last year. The test results are summarized in this paper and discussed.

The alternative pulse reduction algorithm for three-phase voltage-source inverter

Our purpose is to reduce the power loss in three-phase voltage-source inverters. We describe a switching algorithm that uses the conventional PWM method in the low modulation range and alternative discontinuous PWM (ADPWM) in the high modulation range to reduce the switching loss in three-phase inverters. The algorithm reduces the switching loss to 40% that of the conventional PWM method. The experimental and simulated results of a prototype are presented. A way of controlling the shapes of voltage applied ADPWM is provided.