State of Charge Estimation for Lithium-ion Battery Based on Cubature Kalman Filter with Fading Square-foot Factor

Abstract

Abstract The state of charge (SOC) is the key issue to ensure the safe operation of the battery, but the battery system’s state estimation often has low accuracy and robustness under complex conditions or uneven measurement problem. To solve this problem, this paper proposes an SOC estimation method based on the combination of cubature Kalman filtering, fading factor and square root filtering. In addition, the second-order equivalent model is adopted, and parameters are identified. To verify the success of the algorithm, various operation tests were conducted. The simulation results agree well with the experimental results, and the maximum error can reach 3%. Numerical analysis shows that the method has good convergence and robustness under the initial error disturbance.