Dual-Layer Inductor Active Equalization Control for Series-Connected Lithium-Ion Batteries Based on SOC Estimation
Xiaofei Liu, Hui Pang, Yuanfei Geng
Abstract
In order to reduce the time and improve the balancing speed of traditional single-layer inductive equalization circuits, this paper proposes an active equalization control strategy with double-layer inductors for series-connected battery packs, based on an accurate state-of-charge (SOC) estimation. By selecting the inductor as the intermediate energy storage element, the SOC of the single lithium-ion battery (LIB) cell is calculated by using a particle filter (PF) algorithm. Meanwhile, according to the deviation in SOC among the batteries, stop parameters are introduced to achieve the design and optimization of the equalization strategy. Finally, the relationship between the equalization current and the control signal period is derived to fulfill the equalization. The experimental results show that, compared with the traditional single-layer inductive equalization topology, the proposed equalization control topology can shorten the equalization time by at least 15.6%. More importantly, this equalization scheme overcomes the disadvantage of the long energy transfer path of traditional inductive equalization, which helps to improve the equalization speed and the inconsistency of the battery pack.