车载动力电池液体冷却非线性优化方法研究

Nonlinear Optimization Method for Liquid Cooling of Vehicle Power Battery

电动汽车动力电池散热需求会受到外部环境温度、风速和负载电流变化等因素的影响,如果不及时散热,动力电池的温度会迅速攀升,进而影响电动汽车的驾驶性和安全性。基于此提出一种锂离子电池非线性冷却优化方法。首先,通过对锂离子电池生热、散热机理分析,建立考虑传热系数随冷却液流速变化的锂离子电池集中热模型,通过电池特性测试试验确定电池内阻和熵热系数等热物性参数,并与AMESim模型对比,验证模型的有效性。然后,基于电池冷却系统非线性和易受负载电流变化影响的特征,提出一种考虑电池冷却系统的稳态特性以及参考变量前馈功能和闭环反馈消除静态误差机制的非线性冷却优化方法,并对其稳定性和鲁棒性进行研究。仿真结果表明:在NEDC-HWFET-US06组合工况下,非线性冷却优化方法调节下的电池温度与目标温度的最大偏差较PID方法减小了0.8 K,并且冷却过程的能耗降低了6.3%,具有更好的调节效果。

The heat dissipation requirements of electric vehicle power batteries are affected by factors such as external ambient temperature,wind speed,and load current changes.Untimely heat dissipation causes the temperature of the power battery to increase rapidly,thus affecting the driving performance and safety of electric vehicles.Therefore,a nonlinear cooling optimization method for lithium-ion batteries is proposed herein.First,by analyzing the heat generation and heat dissipation mechanisms of lithium-ion batteries,a lumped thermal model of lithium-ion batteries accounting for the change in the heat transfer coefficient with the coolant flow rate was established,and the thermal physical parameters,such as the battery internal resistance and entropy heat coefficient,were determined via battery characteristic test experiments.Additionally,the model was validated by comparing it with the AMESim model.Second,based on the nonlinear characteristics and susceptibility to load current changes of the battery cooling system,a nonlinear cooling optimization method considering the steady-state characteristics of the battery cooling system,which contains a reference variable feedforward function and a closed-loop feedback mechanism to eliminate static errors,was proposed.Its stability and robustness was investigated.Simulation results show that under the NEDC-HWFET-US06 combined condition,the maximum deviation between the battery and target temperatures regulated by the nonlinear cooling optimization method is reduced by 0.8 K as compared with the PID method,and the energy consumed during the cooling process is reduced by 6.3%,which offers a better regulation effect.