Decentralised control method of battery energy storage systems for SoC balancing and reactive power sharing

Abstract

Battery energy storage systems (BESSs) are important for the operation and optimisation of the islanded microgrid (MG).However, the BESSs will have different dynamics due to the differences in characteristics and operating conditions, leading to unbalanced state-of-charges (SoCs). On the other hand, because of the unequal line impedances, the conventional reactive power-voltage (Q–V) droop control results in disproportional reactivepower-sharing. To deal with suchissues, a power -frequency (P–f) droop-based decentralised SoC balancing strategy is developed first to regulate the active power outputs of BESSs in terms of SoCs, thus ensuring SoC balancing among BESSs. Furthermore, the authors develop a Q–V droop-based decentralised reactive power-sharing strategy to dispatch the reactive power among BESSs in terms of their respective reactive power ratings. In this way, compared with the existing control strategies, the proposed control method is fully decentralised, which removes the necessity for both the central controller and communication links. Moreover, the proposed control method has a simpler control structure with the plug and play capability. Finally, the simulation results are presented in an islanded MG to demonstrate the effectiveness, plug and play capability of the proposed control method.