Coordinated and stable control of a hybrid energy storage system for wave generation system

Abstract

When wave generation system works in the grid connected condition, the randomness and intermittence of wave energy at different time scales have a serious impact on power grid. In addition, the scheduling ability of system also needs to improve. In order to solve these problems, a type of hybrid energy storage system (HESS) based on flywheel-battery topology is proposed in this paper. According to the characteristics of flywheel energy storage system (FESS) and battery energy storage system (BESS), the different charge & discharge control strategies are adopted respectively. The hybrid energy storage controller (HESC) is designed to control the HESS, and it can make decisions timely. The redundant power will be distributed to FESS and BESS through low pass filter algorithm at the charging state. At discharging state, FESS and BESS will compensate the loss of power at different speed with the changes of coordinated coefficient k. Finally, the energy distribution of HESS is coordinated controlled to prevent the battery from overcharging or over-discharging. The simulation results not only prove that the HESS can effectively streamline the active power of the wave generation system in grid connected mode, but also lay a solid foundation for thorough research on larger capacity HESS and more complex microgrid operation conditions.