An Improved Distributed Cooperative Control Strategy for Multiple Energy Storages Parallel in Islanded DC Microgrid

Abstract

This article proposes an improved distributed cooperative control strategy for the energy storage system (ESS) in islanded dc microgrid. To meet the requirements of state of charge (SoC) balance, accurate current sharing, and voltage regulation, a hierarchical control structure is established. In the primary control layer, the droop coefficient is adaptively adjusted through the SoC dynamic changes in each energy storage unit (ESU) to achieve SoC balance, and two balance adjustment factors are introduced to improve SoC convergence speed and accuracy. In the secondary control layer, an information state factor <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\zeta $ </tex-math></inline-formula> is designed to eliminate the influence of the inconsistent line resistance on the SoC balance and realize the dc bus voltage recovery. In the communication layer, each ESU only exchanges information with neighboring nodes through a sparse communication network, in which a dynamic consensus algorithm is used to achieve stable convergence of global average information. Finally, a dc microgrid simulation model and StarSim HIL experimental platform are built. The results show that the proposed control strategy can achieve SoC balance and accurate load current sharing under a variety of complex operating conditions and have excellent plug-and-play performance.