Dynamic SOC Balance Strategy for Modular Energy Storage System Based on Adaptive Droop Control

This paper proposes a dynamic state-of-charge (SOC) balance control strategy for the modular super capacitor energy storage system (ESS). The strategy takes SOC information as the droop variable and introduces the SOC of each module into its independent current closed loop by inverse droop control, so that the system can adjust the average operating current of each sub-module according to its SOC in the system dynamic charging and discharging process. Moreover, a concise unified current compensation method is proposed to minimize system current deviation caused by the balance algorithm. Compared with the traditional control strategies, the proposed strategy does not need to exchange SOC information between sub-modules, thus effectively reduces system communication data. In addition, the proposed strategy not only has favorable voltage control ability and stability, but also has a concise control structure. The proposed balance control strategy can further improve the modularity and reliability of the modular ESS, which is helpful to promote the application of the system in medium and high voltage applications.