车用并联电池组不均衡电流建模与仿真分析

Study on Modelling and Analysis of Imbalanced Current inside Parallel-connected Lithium-ion Batteries for Electric Vehicle

车用锂离子电池在实际使用过程中通常需要进行串并联以满足功率输出和能量存储的需求。然而电池间不一致带来的并联电池组内不均衡电流会影响电池组寿命和安全。建立一种N节单体电池并联的电池组等效电路模型。试验结果表明,此等效电路模型在稳态和动态工况均有较好的精度。此等效电路模型可以用于预测并联电池组内部的不均衡电流,分析不均衡电流的分配原理。仿真分析结果表明,容量和内阻的不一致性增加会带来并联电池组内部不均衡相对量IRe和SOCRe的增加。容量增加20%,IRe增加17.0%,SOCRe增加3.7%;内阻增加100%,IRe增加18.2%,SOCRe增加5.7%。

Lithium-ion batteries are always connected in series and parallel in order to fulfill its functional usage.However,imbalanced current caused by cell variations has significant impact on the life and safety of battery pack.An equivalent circuit model for battery pack composing of cells connected in parallel is introduces.Experimental results show that the model has good accuracy under both steady and dynamic working loads.The proposed method simulates current distribution among parallel-connected cells and can help analyze the behaviors of current distribution.Simulation results show that the increase of the relative quantity IRe and SOCRe representing imbalanced current and state of charge(SOC)variation can be caused by the increase of battery capacity and resistance variation.20%increase in capacity leads to IRe increasing by 17.0%and SOCRe increasing by 3.7%,while 100%increase in resistance leads to IRe increasing by 18.2%and SOCRe increasing by 5.7%.