Development of the mutual energy exchanging system between areas by the direct-current system which utilized renewable energy

This paper reports on an experimental study for the development of an energy exchanging system between areas based on direct current (DC) using renewable energy. It includes demonstrations that are being held at two sites in Japan: Obihiro City in Hokkaido and Yamagata City in Yamagata prefecture. The demonstration at the Obihiro site involves the development of elemental technologies needed for implementing a practical DC power feed, such as DC conversion equipment, DC peripheral devices, and a DC energy management system, and the construction of a DC microgrid based on photovoltaic (PV) power generation and storage batteries. The DC equipment developed here showed a 3-5% improvement in efficiency compared to existing alternating current (AC) equipment having the same functions. The demonstration at the Yamagata site involves the construction of a microgrid in each of three areas within the site and the development of an energy-exchanging system using both DC and AC interfaces. It includes energy-exchanging simulations using actual operational data and testing of facility-capacity reduction with a 40% reduction in storage battery capacity set as a target.