I. Introduction
In consideration of environmental issues, an introduction of renewable energy sources such as photovoltaic (PV) power generation is being actively promoted for electric power grid [1]. Also, battery energy storage (BES) is used to match the power balance and maintain an operation in power grids [2]–[4]. In addition, compare to conventional AC distribution system, DC microgrid, an independent DC distribution system becomes attractive since an increase of electric DC devices and an ease of control [5] [6].