A Fully Filter-Based Decentralized Control With State of Charge Balancing Strategy for Battery Energy Storage Systems in Autonomous DC Microgrid Applications

State of charge (SoC) imbalance and dc bus voltage deviations are significant issues for distributed battery energy storage systems in autonomous dc microgrid applications. Accordingly, a high-pass filter (HPF) based SoC balancing method is proposed to achieve SoC balance by considering different SoCs and capacities; A band-pass filter (BPF) based power droop control is used to accomplish power-sharing and voltage compensation. Through this approach, battery storage units (BSUs) with higher SoC and capacity deliver more power during discharging mode than those with lower SoC and capacity. During charging mode, those BSUs with higher SoC and lower capacity are controlled to absorb less power than those with higher capacity and lower SoC. Therefore, SoC balance can be achieved between distributed BSUs. Further, the dc bus voltage is maintained within the desired range by adopting the proposed method. In addition, the control method employed also considers the impact of line resistance. The proposed control strategy is implemented in a fully decentralized way which does not require any communication link, while maintaining system stability. MATLAB/Simulink and processor-in-the loop (PIL) simulation results verify that the proposed control strategy is effective and feasible.