Optimal Energy Management System for Isolated Micro Grids

Facing the recent growing concern about the environment and electric power crisis triggered by the Great East Japan Earthquake, efficient use of energy has become an important issue. A smart grid that is a next-generation electric power network is expected to be one of the solutions and to form an enormous market. Aiming to enter this new smart grid market, Sumitomo Electric Industries, Ltd. established a special R&D department in January 2010. This department has been actively developing equipment and systems for a smart grid. A smart grid controls the flow of electric power on both the supply and demand sides to ensure efficient use of energy. In particular, a small-scale electric power network comprising dispersed power sources and electrical loads is called a micro grid system. In June 2011, Sumitomo Electric built an isolated micro grid system(1),(2) in its Osaka Works. Separated from the commercial transmission grid of an electric power company, this system uses photovoltaic generators and a wind turbine generator to produce electricity, and a redox flow (RF) battery to store the electricity produced by these generators. Since this micro grid system is isolated and comprises generators that use only renewable energy, the electric power produced by these generators fluctuates sharply, making it difficult for the system to supply electric power with stable quality. This system’s electric power generation also depends on weather conditions, meaning that this system cannot always generate electric power in response to demand. In other words, this system faces two problems: (1) stabilizing the quality of electric power, and (2) supplying electric power in response to demand. To solve these problems, we developed an energy management system (EMS). This paper describes and discusses the verification results of the EMS.