电动汽车锂电池主动充电均衡节能研究

Study on Active Charge Balance and Energy Saving of Lithium Batteries for Electric Vehicles

电动汽车用动力电池组都是由多个单体电池串联而成,由于单体电池的性能不可能完全一致,串联使用过程中,初期的细微差异在每次充放电的放大作用下,一段时间后单体电池间的性能差异就会逐渐增大,从而导致电池组性能急剧下降和循环寿命缩短,其中要解决电池间不一致性的技术难点是均衡电路的设计以及均衡控制策略。针对上述问题提出了基于一种改进的锂电池主动充电均衡方案,以谐振电路为主,利用谐振软开关实现开关的零电流导通和截止,辅助二极管均衡模块来解决谐振电路均衡后期电流过小的问题,实现充电过程中的主动均衡,并依托MATLAB/Simulink软件建立均衡电路模型,通过仿真分析,均衡效率得到了显著改善,电池之间的不一致性得到了明显改善。另外通过对两节3. 7V/2Ah的三元锂电池组进行了充电模式下的均衡实验,实验结果也验证了上述主动均衡方案的有效性。

In electric vehicles, battery string with many ceils in series connection can provide higher voltage. But for each cell, any slight voltage difference can be amplified in charging and discharging cycles. Unbalanced cell voltage in battery string will give rise to serious over - charging or over - discharging, and decrease the total storage capacity and the battery cycle life. One of the technical difficulties to solve the inconsistency between the batteries is the design of balanced circuits and balanced control strategy. An improved charging scheme is proposed based on the analysis of various existing equalization methods. This scheme is mainly based on the quasi - resonant circuit, and supplemented by the diode equalization module to solve the problem that resonant circuit equalization of the late current is too small, which can realize the active equalization in the charging process of battery pack. A balanced circuit model was established with MATLAB/Simulink software and the equilibrium efficiency and inconsistency have been improved significantly through the simulation analysis. In addition, the equilibrium experiment of two - cell lithium battery with 3.7V / 2Ah was carried out. The experimental results also verify the effectiveness of the active equilibrium scheme.