Design of an Active Equalization Scheme with a Modified Circuit and SOC Estimation-Based EKPF

In this paper, an active equalization scheme is proposed to realize the balance of series connected lithium-ion cells. First, a modified dual-layer inductor active equalization circuit is designed, which connects the first cell and the last cell in the group with a new equalization module, and improves the equalization speed. Then, to upsurge the efficacy of balancing control, state of charge (SOC) is estimated by extended Kalman particle filter (EKPF) algorithm and used as equalization variable. Finally, the simulation results show that the modified dual-layer inductor active equalization circuit can shorten the equalization time by 18% at least, effectively reducing the inconsistency of multi-cell lithium-ion battery pack.