Power battery SOC estimation with combination method based on UKF and open circuit voltage

The state of charge (SOC) is an important parameter in the battery management system. The SOC is usually estimated with the battery voltage and other state. Owing to the initial value problem of SOC, the estimation error may increase greatly. In order to solve this problem, the combination method based on unscented Kalman filter (UKF) and open circuit voltage is proposed in this paper. First, the PNGV model is used, and its parameters are identified with HPPC test data. Then, the estimation process is proposed. In order to verify the method, the PNGV battery model is established in the Simulink Toolbox. With the battery model, the SOC combination estimation method was simulated and compared with Ah counting and extended Kalman filter (EKF) methods. The simulation results show that the combination method gives smaller estimation error and calculation amount, so the combination estimation method is promising and useful for estimating the battery SOC.