A Novel Lithium-ion Battery Active Equalization Structure and its Control Strategy Based on Bidirectional Converter Unit

In order to improve equilibrium speed and scalability, a novel type of active battery equalization structure based on bidirectional converter is proposed in this paper. A three-level hierarchical equalization control strategy for this active battery equalization structure is also developed. The balance principles and technologies of battery string, battery equalization module and battery equalization unit are firstly introduced in detail. Subsequently, a small capacity lithium-ion battery equalization system is built up and tested. Experimental results show that this new active equalization system operates normally and realizes the equalization function of the battery SOC fast.