Abstract:In the islanded AC low-voltage micro-grid,the accurate sharing of active power cannot be realized by droop gain of the traditional droop control,which is caused by the unmatched line impedance.Differences of state-of-charge (SOC) will exist inevitably in each distributed energy storage unit (DESU),which leads to overcharge or overdischarge and shorter service life of battery.Therefore,a hierarchical control strategy for distributed energy storage system (DESS) in AC low-voltage microgrids is proposed.The virtual impedance is obtained by the power balancing stage,which eliminates the influence of accurate sharing of active power caused by unmatched impedance.In the stage of SOC balancing,each DESU dynamically adjusts the output active power according to SOC,and SOC deviation decreases with e-index curve,ultimately achieveing SOC balancing of the DESUs during discharging process.The dynamic consensus algorithm is applied for information sharing between the DESUs.It can provide higher system reliability,expandability,and flexibility due to its distributed control architecture.The stability of proposed strategy is analyzed based on small signal theory and the influence of acceleration factor is discussed.The simulation comparison results verify the effectiveness and feasibility of the proposed control strategy.