Hybrid equalization scheme for a lithium-ion battery pack based on a three-winding transformer

In order to solve the problem of inconsistency between cells in lithium-ion battery packs, a hybrid equalization topology based on a three-winding transformer and a group adaptive interleaved control strategy are proposed. The scheme not only has two equalization types, pack to cell (P2C) and cell to pack (C2P), but also adaptively adjusts the equalization type according to the state of the battery pack, so that the equalization circuit always works in the best state and realizes the fast equalization of the battery pack. Through the analysis of speed, efficiency, and cost, it is concluded that the scheme has the characteristics of fast balancing speed, high balancing efficiency, and low cost. Then the experimental analysis was carried out under three working conditions of charging, shelving, and discharging to verify the feasibility of the novel scheme in practical applications.