A novel centralized equalization topology is proposed in this paper to achieve the balancing of series-connected battery packs. The proposed converter topology integrates the polarity switches in the traditional centralized battery equalization system, which can also be regarded as a cascade structure composed of a bidirectional buck-boost converter and a bidirectional flyback converter. This integrated cascade structure enables the proposed topology to have a high voltage conversion ratio when the turns ratio is small, which can significantly reduce the leakage inductance and improve the efficiency of the transformer. Moreover, compared with the conventional equalizers, the proposed method has higher reliability and fewer components count, and is more suitable for the equalization of large-capacity battery packs. The operating principles and design considerations are presented in detail. Finally, an experimental prototype based on a 13-cell battery string is built to verify the excellent performance of the proposed equalization topology.

Battery equalizer,active equalization,lithium-ion batteries,bidirectional dc-dc converter