SOC Balancing Control Strategy of Multiple Energy Storage Units in Photovoltaic-Storage DC Microgrid Based on Improved Adaptive Droop Control

In the stand-alone operation mode of DC microgrids, an energy storage system composed of Energy Storage Units (ESUs) are required to maintain system stability. However, when multiple ESUs operate in parallel, continuous operation under inconsistent State of Charge (SOC) conditions of multiple energy storage units may lead to over-discharge or overcharge of certain ESUs, affecting the service life of energy storage units and the stability of the microgrid. To address this issue, an improved droop control strategy is proposed. By nesting an exponential function within a power function, the sensitivity of the droop coefficient to SOC changes is enhanced, thereby improving the SOC balancing effect. Additionally, a SOC deviation response coefficient is introduced to enable rapid SOC balancing among ESUs. Finally, a simulation model is built based on MATLAB/Simulink, and the simulation results verify the effectiveness of the proposed strategy.