State-of-charge estimation of lithium-ion batteries based on improved H infinity filter algorithm and its novel equalization method.

The state of charge (SOC) estimation and battery equalization method are essential in battery management system (BMS). In this paper, an improved H infinity filter algorithm based on the reverse recursion of historical data which could update the inner parameters of algorithm online is proposed. The battery life decay experiment result shows that open circuit voltage (OCV)–SOC relationship and the actual capacity of battery have a great impact on the SOC estimation accuracy based on H infinity, and the max SOC estimation error can exceed 15%. The improved H infinity algorithm proposed in this paper can keep the SOC error within 3% and its convergence to the true SOC is faster than the sliding mode observer algorithm. On this basis, a novel equalization strategy based on shunting is proposed. The equalization strategy model is simulated in SIMULINK, and as compared with the general cell bypass methods, the proposed method utilizes a redundant cell to achieve a high efficiency beyond 99%. The analysis results show that the 6Ah redundant cell could decrease the inconsistence of SOCs to 2%. • The SOC estimation based on H infinity filter algorithm is introduced for equalization strategy. • An improved H infinity filter algorithm based on reverse recursion of historical data is proposed. • The equilibrium efficiency higher than 99% is achieved using the proposed balancing method. • A 6Ah redundant cell could improve the in consistence of SOCs to 1.5%. [ABSTRACT FROM AUTHOR]