Abstract Lithium batteries are widely used in the new energy sector due to their high energy density and low self-discharge rate. As the capacity of each battery unit is different, overcharging and over-discharging greatly affect the battery life. This paper focuses on the safety of series lithium batteries. Firstly, the existing series of lithium battery equalization circuits are summarized, and the advantages and disadvantages of different circuits are analyzed. Regarding the disadvantages of multi-winding transformer-type equalization circuits, this paper proposes a Lithium-ion battery equalization circuit based on a bidirectional half-bridge CLLLC resonant converter. Secondly, the working principle and mode of the bidirectional half-bridge CLLLC resonant converter are explained, and its resonance and gain characteristics are analyzed using fundamental analysis. In addition, a control method for synchronous rectification of the secondary side of the half-bridge CLLLC resonant converter is proposed. Then, for the proposed Lithium-ion battery equalization circuit, the operating principles of its four equalization paths are analyzed, and the equalization current expressions for each path are derived. The parameter design method of the equalization circuit is given according to the analysis of the bidirectional half-bridge CLLLC resonant converter. Based on the four equalization paths of the equalization circuit and the different purposes of dynamic and static equalization, two equalization strategies are proposed. Finally, the relevant hardware parameters of the equalization circuit are designed, and the device selection is carried out. The fabrication method of the magnetic components is also given. A set of equalization circuits for six battery cells is built. The equalization path and the soft circuit switching are verified by simulation and experiment. According to the proposed control strategy, static equalization and dynamic equalization are carried out for six battery cells. The experimental results show that the proposed equalization circuit has the advantages of a flexible equalization path, fast equalization speed, high equalization efficiency, and a half number of windings.
Cai Ruijia,Ma Yundong,Wang Pengfei等. Lithium-Ion Battery Equalization Circuit Based on Bidirectional Half-Bridge CLLLC Resonant Converter[J]. Transactions of China Electrotechnical Society, 2024, 39(15): 4868-4882.
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2024, Vol. 39 
