Research on Hierarchical Active Equalization Control of Series Lithium-ion Battery Pack Based on Model

Aiming at the inconsistency of series lithium-ion battery pack, a model-based hierarchical active equalization control method is proposed by taking the state of charge (SOC) of the battery cell as the equalization object. The battery pack model is established with Modelica language, and the battery equalization topology is established based on the hierarchical active Buck-Boost circuit. The model of SOC estimation algorithm is carried out by unscented Kalman filter (UKF) with Simulink, and the equalization judgment criterion is based on the SOC deviation threshold between cells. The FMI (Functional Mock-up Interface) standard is applied to realize the co-simulation experiment between the battery pack model of Modelica and the equalization control model of Simulink. Simulation results reveal that under two different current conditions, the proposed method can effectively improve the SOC inconsistency of the series battery pack, and the maximum SOC deviation between cells is reduced from 13.2% to 0.5%.