SoC Balancing Strategy for Multiple Energy Storage Units With Different Capacities in Islanded Microgrids Based on Droop Control

Due to the differences of line impedance, initial state-of-charge (SoC), and capacities among distributed energy storage units (DESUs), the SoC of the DESUs with different capacities in an ac islanded microgrid will be unbalanced when using the conventional droop control. A droop control based on the SoC balancing scheme is introduced in this paper to eliminate the influence of capacity on SoC balancing and maintain a good power quality. The proposed control strategy does not require communications or central controller, and the scalability of system is greatly improved. The effectiveness of the proposed approach has been validated by simulation and experimental results.