A modular equalization method for series-connected battery packs based on inductors

Abstract

When lithium batteries are used in energy storage systems, due to the low voltage of cells, it is necessary to connect multiple cells in series to form a battery pack that meets the application requirements. There is an unavoidable consistency difference between cells of the same type, and after the cells are formed into a group, the consistency difference will have a serious impact on the cycle life, and jeopardize the safety of the battery pack. To improve the consistency difference of series-connected battery packs, a modular hierarchical active equalization method based on inductors is proposed. First, the topology is proposed in combination with the high accuracy of inductor-based equalization, and its working principle and parameter design are analyzed. Second, based on the equalization principle, a matching adaptive equalization control strategy is designed. Again, the equalization performance of the proposed equalization method is analyzed, which shows that the proposed method has the advantages of fast equalization speed, low topological cost and simple control. Finally, an experimental platform for the equalization of a 9-cell series-connected battery pack is established to verify the effectiveness of the proposed equalization method. The proposed method can significantly improve the consistency difference of the series-connected battery pack, and then improve its energy utilization and cycle life.