Optimal sizing and control strategy of isolated grid with wind power and energy storage system

•An energy storage sizing scheme for wind powered isolated grid is developed.•A bi-level control strategy for wind-battery isolated grid is proposed.•The energy storage type selection method for Nan’ao island grid is presented.•The sizing method and the control strategy are verified based on the Nan’ao island.•The wind-battery demonstration system has great benefit for remote areas. Integrating renewable energy and energy storage system provides a prospective way for power supply of remote areas. Focused on the isolated grids comprising renewable energy generation and energy storage, an energy storage sizing method for taking account of the reliability requirement and a bi-level control strategy of the isolated grids are presented in this paper. Based on comparative analysis of current energy storage characteristics and practicability, Sodium–sulfur battery is recommended for power balance control in the isolated grids. The optimal size of the energy storage system is determined by genetic algorithm and sequential simulation. The annualized cost considering the compensation cost of curtailed wind power and load is minimized when the reliability requirement can be satisfied. The sizing method emphasizes the tradeoff between energy storage size and reliability of power supply. The bi-level control strategy is designed as upper level wide area power balance control in dispatch timescale and lower level battery energy storage system V/f control in real-time range for isolated operation. The mixed timescale simulation results of Nan’ao Island grid verify the effectiveness of the proposed sizing method and control strategy.