Error analysis of SOC estimation based on PI observer

The PI observer model for SOC estimation of battery is established based on the first order Thevenin model. On the basis of this model, we analyze the factors influencing the model parameters of battery and the trend of parameters. Based on state equations of SOC, steady state error of SOC estimation is deduced theoretically, and a practical example is provided. From the example can we see, SOC estimation based on PI observer is affected by the accuracy of the parameters such as the internal resistance, the open circuit voltage and the capacity of the battery model, and these factors have different extent of influence. The simulation results show that this model can accurately estimate the SOC of the battery with exact parameters.