Research on Optimization of Control Strategy for Energy Storage Systems Considering Battery State of Charge

ObjectivesDistributed energy storage systems exhibit slow state of charge (SOC) equalization and low current distribution accuracy due to inconsistency in the SOC and capacity among battery cells. To address these issues, a control strategy for energy storage systems that considers SOC for energy storage units with different capacities is proposed.MethodsThe strategy improves droop control by integrating the SOC difference with the droop coefficient using an inverse tangent nested power function. The variable acceleration factor in the droop coefficient is dynamically adjusted according to the SOC difference to achieve better equalization. Additionally, virtual voltage and DC bus voltage compensation are incorporated to achieve accurate output current distribution while ensuring bus voltage stability.ResultsThe optimized variable acceleration factor reduces the SOC equalization time by approximately 50% compared to the fixed acceleration factor. The output current remains consistent with the capacity ratio without compromising SOC equalization performance.ConclusionsThis control strategy improves SOC equalization speed and output current distribution accuracy among energy storage units with different capacities.