By social and technical reasons, the amount of the distribution generation will considerably increase in the future power supply system. For the secure supply and the safe operation of the distributed generation (DG) power, the harmonized grouping of DG plants and the careful interconnection of the DG micro grid to the existing power grid are required. This paper discusses the DG grouping in order to harmonize the investment of assets, the quality of power supply and the cooperation with the existing power grid. Model analysis shows there are several schemes of the DG plants and the storage device related to the combination of economical parameters. Recently, the demonstration research projects of DG grouping have been performed in Japan. Brief description of these projects is also included.