An Improved SOC Equalization Control Strategy for Distributed Energy Storage in DC Microgrid

Distributed energy storage systems in DC microgrids are crucial for stabilizing bus voltage and maintaining system power balance. To address the issue whereby varied states of charge (SOC) of distributed energy storage units may lead to over-charging or over-discharging, thus affecting the stability of the system, this paper proposes an improved SOC equalization droop control strategy. This strategy introduces a variable acceleration factor based on the traditional exponential SOC droop control strategy, aimed at further accelerating the equalization speed in the presence of minor differences in SOC, and simultaneously limiting the maximum value of the storage unit's output power to improve the reliability of the system. Meanwhile, to address the issue of bus voltage deviation arising from the equalization process, a secondary voltage compensation control is introduced to restore the bus voltage to the rated value. Finally, a simulation model for the photovoltaic storage DC microgrid system was constructed using MATLAB/Simulink, which confirmed that the proposed control strategy effectively ensures the rapid equalization of the SOC of distributed energy storage units, while maintaining power balance and bus voltage stability of the microgrid.