Dynamic allocation method of DC side power based on improved ratio control for STATCOM/BESS

The degradation of power quality induced by the intermittence of renewable energy generation in microgrids can be solved by using parallel battery energy storage system (BESS) at the DC side. Consequently, when multiple BESSs are simultaneously connected at the DC side of static synchronous compensator (STATCOM), a DC side dynamic power sharing method based on improved proportional control is proposed in order to balance the power of each BESS. The state-of-charge (SoC) of each BESS is selected as the control objective in the proposed method, and proportional control with variable coefficients is employed to determine the power dispatch among multiple BESSs. It is achieved that the module with higher SoC delivers more power, while the one with lower SoC absorbs more power. Meanwhile, when the system only generates reactive power, the module with higher SoC can charge the one with lower SoC. With on-line dynamic adjustment of the proportional term, fast dynamic power dispatch can be achieved, which can further enhance the utilization rate of the module. The correctness of the proposed control method is verified by using simulation and experimental tests.