DC 마이크로그리드에 연계된 ESS의 SoC 밸런싱을 위한 옵셋 전압 기반 드룹 제어 기법

This paper proposes a droop control based on offset voltage for SoC balancing of ESS in DC microgrid. When multiple energy storage systems are operated, SoC unbalance decrease the lifetime of ESS and excessive high or low SoC deteriorate charging/discharging performance of the ESS. Therefore, in this case, SoC balancing control considering the SoC operating range is required. The proposed method controls the charging/discharging current by adding an offset voltage to the voltage reference of the droop-controlled converter of energy storage systems so that the SoC of each system can be balanced without communication. Also the offset voltage considers the operating range of the SoC, so that the charging/discharging current is limited at the boundary of the SoC operating range to prevent overcharge and overdischarge. The proposed droop control method for energy storage systems in DC microgrid is verified by simulation and experiment results.