Research On Distributed Control Strategy Based On Cascaded H-Bridge Battery Energy Storage System

Cascaded H-bridge topology has been used in grid-tied converter for battery energy storage system due to its modular structure.To fully utilize the converter's modularity,we propose a hierarchical distributed control architecture that consists of primary control and secondary control.Primary control guarantees a good current tracking performance and is a decentralized control strategy without the need of any communication.Meanwhile,a carrier phase shift control is implemented to deal with the synchronization issue between module controllers and obtain multilevel output voltage and lower ripple output current.However,the converter operates in an undesired unbalanced state with only primary control,where each module outputs non-uniformed active and reactive power.A secondary control scheme based on distributed consensus algorithm is proposed to generate equal voltage and power output among modules.The proposed secondary control scheme only requires a low bandwidth communication network to share information.The analysis presented in this paper shows that both output current regulation and equal power sharing can be achieved by the proposed hierarchical distributed control architecture.Additionally,a battery SOC balancing control scheme is proposed to obtain higher energy utilization efficiency.Based on the secondary control scheme,a power proportional distribution control scheme is proposed.The active power distribution ratio among modules is regulated by the inconsistency of the battery SOC,and then SOC balancing is realized by controlling the battery charge and discharge current.Achieve SOC equalization between battery modules.Finally,an experimental platform for cascaded H-bridge battery energy storage system was built.The effectiveness of the presented control strategy is verified through experiments.