SoC Balancing Strategy of Multi Energy Storage System in Islanded Microgrids Considering Acceleration Factor Setting

In accordance with the issue of unbalanced state of charge (SoC) of battery energy storage system (BESS) in islanded AC microgrid, an improved droop control strategy is presented. Based on conventional P-f droop control, the scheme introduces the equalization factor in the form of exponential function to change the droop coefficient, consequently SoC equalization of BESS with different capacity is achieved by regulating the output power of the inverter. Furthermore, the small signal model of multi-inverter parallel system is established to explore the effect of acceleration factor on system stability, then the design basis of acceleration factor is discussed. In the end, the simulation example under various conditions demonstrates the availability of the improved control scheme and the correctness of the acceleration factor setting.