基于SOC的锂离子电池组主动均衡系统的研究

Research on Active Balance System of Li-ion Battery Pack Based on SOC

电动汽车锂离子电池组各单体电池间存在的差异性会影响电池的使用寿命,会降低电池容量的利用率,故需要对锂离子电池组进行均衡。本文设计了一种以电池荷电状态(state of charge,SOC)作为均衡策略的一致性准则,且选取电感式均衡电路实现锂离子电池组的主动均衡。同时,采用带遗忘因子的递推最小二乘法(Recursive Least Squares with Forgetting Factor,FRLS)对锂离子电池带有温度补偿的Thevenin等效电路模型参数进行辨识和更新,与无迹卡尔曼滤波算法(Unscented Kalman Filter,UKF)实现电池SOC在线估计,估算误差控制在2%以内。最后对设计的主动均衡策略进行仿真验证,结果表明,该均衡系统改善了电池组中各单体电池间的差异性,提升了电池容量的利用效率,促进电动汽车行业的发展。

The differences between the individual cells of the lithium-ion battery pack of electric vehicles will affect the service life of the battery and reduce the utilization rate of the battery capacity.Therefore,the lith-ium-ion battery pack needs to be balanced.This paper designs a consistency criterion based on the state of charge(SOC)of the battery as a balancing strategy,and selects an inductive balancing circuit to achieve active balancing of lithium-ion battery packs.At the same time,the Recursive Least Squares with Forgetting Factor(FRLS)method is used to identify and update the parameters of the Thevenin equivalent circuit model of the lithium-ion battery with temperature compensation,and the Unscented Kalman Filter algorithm(UKF)realizes online estimation of battery SOC,and the estimation error is controlled within 2%.Finally,the designed active balancing strategy is simulated and verified.The results show that the balancing system improves the differ-ence between the individual cells in the battery pack,improves the utilization efficiency of battery capacity,and promotes the development of the electric vehicle industry.