Electrochemical Model based State of Charge Estimation for Lithium Batteries with Backstepping Techniques

In this paper, state of charge (SOC) estimation based on the lithium-ion battery electrochemical model is considered. The battery electrochemical model, which is given by partial differential equations (PDE), can describe the variation process of lithium-ion concentration during charging and discharging very well. And with the charging and discharging cycle number increasing, the electrochemical model parameters will change, such as the diffusion coefficient in the battery. In order to estimate the SOC well, passive identifier method is applied to identify the diffusion coefficient in the electrochemical model. Then a PDE observer based on backstepping technique is proposed to estimate the SOC in the battery, and Crank-Nicolson-Method is used to solve PDE. The simulation results indicate that proposed estimation method based on backstepping for SOC estimation in lithium-ion battery has good performance.