并联锂离子电池组建模及不均衡电流分析

Modeling and Unbalanced Current Analysis of Parallel Lithium-ion Battery Packs

近年来电池储能以其响应速度快、能量密度高等优点,在电力系统中发挥重要作用。为满足实际应用的要求,电池储能系统需要将电池或电池组并联从而达到较高的可用容量,但并联电池在实际中受内阻、容量、荷电状态(SOC)等影响将出现电流不平衡现象,一定程度上制约了电池充放电电流和使用条件,影响了电池性能。针对并联电池组支路电流采集过程繁琐且状态估计复杂的情况,以电池的二阶等效电路为基础,结合回路电流法建立了并联电池组的仿真模型。模型能够根据锂电池的性能参数及状态方程实现并联支路电流的计算,进而估计并联电池组的状态,省去了对并联支路电流的检测环节。同时重点研究了并联电池组的支路不均衡电流现象,以磷酸铁锂电池为例,分析了并联电池组的充电特性。针对并联电池组的支路不均衡电流影响因素较为复杂、难以解耦的特性,采用控制变量法,通过模型详细分析了内阻、容量、初始SOC等因素对支路电流点的影响,为并联电池组的设计、成组优化及性能分析提供了参考。

In recent years,battery energy storage has played an important role in power systems due to its fast response speed and high energy density.In order to meet the requirements of practical applications,battery energy storage systems need to connect batteries or battery packs in parallel to achieve a higher usable capacity,but in practice,parallel batteries will have current imbalance due to internal resistance,capacity,SOC,etc.,to a certain extent.The above factors restrict the battery charging and discharging current and usage conditions,and affects the battery performance.Aiming at the cumbersome process of collecting the branch current of the parallel battery pack and the complicated state estimation,a simulation model of the parallel battery pack is established based on the second-order equivalent circuit of the battery and the loop current method.The model can calculate the current of the parallel branch according to the performance parameters of the lithium-ion battery and the state equation,and then estimate the state of the parallel battery pack,eliminating the need for the detection of the current of the parallel branch.At the same time,it focuses on the phenomenon of unbalanced current in the branches of parallel battery packs.Taking lithium iron phosphate batteries as an example,the charging characteristics of parallel battery packs are analyzed.In view of the complicated and difficult-to-decouple characteristics of the unbalanced current in the branch circuit of parallel battery packs,the control variable method is adopted to analyze the influence of the internal resistance,capacity,initial SOC and other factors on the branch current point in detail through the model.The results to provide a referencedesign,group optimization and performance analysis of the battery pack.