DC Micro-grid for Super High Quality Distribution — System Configuration and Control of Distributed Generations and Energy Storage Devices —

"DC micro-grid" is the novel power system using dc distribution in order to provide super high quality power. The dc distribution system is suitable for dc output type distributed generations such as photovoltaic and fuel cells, and energy storages such as secondary batteries and electric double layer capacitors. Moreover, dc distributed power is converted to required ac or dc voltages by load side converters, and these converters do not require transformers by choosing proper dc voltage. This distributed scheme of load side converters also contributes to provide supplying high quality power. For instance, even if a short circuit occurs at one load side, it does not effect other loads. In this paper, we suppose one system configuration of DC micro-grid, and propose control methods of converters for generations and energy storages. Computer simulation results demonstrated seamless turn-on and turn-off operation of a distributed generation, a transient of connecting and disconnecting operation with a bulk power system, and the stability for sudden large load variation.