Dynamic Correction Strategy for SOC Based on Discrete Sliding Mode Observer

Battery state estimation is one of the most important decision parameters for lithium battery energy management. It plays an important role in improving battery energy utilization, ensuring battery safety and enhancing system reliability. This paper is proposed to provide a dynamic correction of SOC in the full working condition, including static condition and dynamic condition. Based on the Coulomb-counting method, the current SOC value of the battery is calculated. Under the static conditions, the open circuit voltage of the battery is used to directly collect the initial SOC. Under the dynamic working conditions, the open circuit voltage of the battery is estimated by the sliding mode observer. Based on the deviation between the calculated and estimated values of the open circuit voltage, the current coefficient of the Coulomb-counting method is dynamically corrected by PI strategy. The research shows that the proposed strategy can effectively correct the deviation of SOC in the initial process and the discharge process, and avoid the problem that the existing “open circuit voltage + Coulomb-counting” method cannot dynamically correct the SOC deviation. When an upward deviation or a downward deviation occurs, the proposed method can quickly eliminate the deviations.