A Family of Integrated Cascade Multiport Converters for Centralized Equalization Systems: Derivation, Analysis, and Verification

Abstract

To achieve simultaneous balancing of multiple battery cells, existing centralized equalization methods need to configure multiple converters, which results in large size and high cost that limit the application of such methods. In this article, a systematic approach for deriving integrated cascade multi-port converters (ICMPC) is proposed, and the limitations of existing centralized methods are addressed by the derived family of converters. In the ICMPC-based method, the energy exchange between multiple unbalanced cells and battery string can be realized by configuring only one converter, which greatly improves the power density and cost benefit. Besides, the ICMPC features high voltage gain, high efficiency and easily expandable ports, which further enhances its application potential. In order to better understand the derived converters, the half-bridge based ICMPC with voltage dividing capacitors is thoroughly studied, covering its operation principle, control strategy, parameter selection and soft-switching analysis. Finally, a test prototype for equalizing a battery string consisting of two 7-cell modules is built to validate the theoretical analysis. Also, an in-depth comparative evaluation is carried out to confirm the superiority of the ICMPC-based equalization system.