关键词: 锂电池, 二阶RC等效电路模型, 参数辨识, 最优化, 参数初始值

Abstract:

The establishment of an accurate battery model is critical for the estimation of SOC (state of charge) and SOH (state of health).The accuracy of model mainly depends on two aspects: the determination of the model kind and the identification of model parameters. The research shows that the second?order dynamic lithium?ion battery model can effectively simulate charging and discharging process. So this paper mainly focus on the second?order model of lithium battery. The problem of parameters identification of the model can be reduced to a nonlinear optimization problem. Firstly,a corresponding nonlinear least squares optimization model is established. Then the optimal identification results of the parameters are obtained by the Levenberg?Marquard algorithm. However the optimization problem is not only non?linear,but also non?convex. So the selection of the initial value of RC parameters is important to the outcome of the algorithm. At the same time,the variation of the discharge current will also affect the identification results. In order to solve these two problems,this paper first proposes a simple and effective method for selecting the initial value of RC parameters and a method for adjusting the objective function in the optimization model to ensure the algorithm can obtain correct solutions under different discharge current conditions. Parameters under different soc are identified by this method. The simulation results show that the algorithm can quickly and accurately obtain the RC parameter values in the model when a suitable initial value is selected.

Key words: lithium battery, second?order RC equivalent circuit model, parameter identification, optimization, initial parameter value