Robustness Evaluation of Unscented Kalman Filter for State of Charge Estimation Based on Battery Capacity Degradation Model

In this paper, a robustness evaluation of Unscented Kalman Filter (UKF) in comparison with the Extended Kalman Filter (EKF) for State of Charge (SOC) estimation of a lithium-ion battery based on capacity degradation model is investigated. To more comprehensively evaluate the performance of EKF and UKF, A first-order RC equivalent circuit model was used to characterize the dynamic behavior of a 30Ah lithium-ion battery. Based on the relationship between the Arrhenius formula, battery capacity, temperature and charge-discharge current accelerated stress, a fitting formula is obtained to predict the battery capacity degradation rate. The simulation results show that UKF outperforms EKF in terms of estimation accuracy and convergence rate against temperature effects, current and voltage noises.