In this article, an isolated bidirectional dc-dc converter with an integrated cascade structure is proposed for a centralized charge equalization system. Compared with existing architectures, the proposed converter structure is equivalent to the integration of polarity switches and a bidirectional dc-dc converter. Equalization of cells with different voltage polarities can be realized by controlling the working state of the converter, which further improves the reliability and integration of the equalization system. The integrated cascade structure can not only increase the equalization current and make it work in a continuous state but also achieve a high voltage conversion ratio to improve the efficiency of the transformer. Theoretical derivations of the converter and the conditions of soft-switch implementation are analyzed in detail. Finally, equalization experiments on a 13-cell lithium-ion battery string are carried out, and a quantitative and comprehensive comparison of different centralized equalizer is conducted. The experimental and comparison results validate the superiorities of the proposed equalizer and demonstrate obvious performance enhancement over the conventional method.

This article presents a novel integrated cascade bidirectional dc–dc converter for optimizing a centralized charge equalization system. Through the integrated cascade structure, the polarity switches and the bidirectional dc–dc converter in the traditional centralized system are integrated, and the cells with different voltage polarities are equalized by controlling the operating state of the converter. Compared with the conventional methods, the number of active switches is significantly reduced, leading to a more compact size and a higher reliability. Moreover, with a phase-shifted pulsewidth modulation strategy, the peak value of the transformer current is reduced and the soft-switching operation is realized, thus greatly reducing the transformer and switching losses. Finally, the experimental results on 13 series-connected battery cells show that the proposed scheme exhibits the excellent performance in terms of equalizing efficiency and speed. The performance improvement of the proposed equalizer is further validated by a systematic comparison with the conventional centralized equalization methods.

This article presents a systematic topology derivation method for developing integrated cascaded bidirectional (ICB) converters, and the centralized charge equalization system can be optimized with the proposed family of converters. On the basis of the traditional centralized system, the proposed ICB converters are generated by integrating the polarity switches and different bidirectional dc–dc converters. Compared with existing methods, the ICB converter-based centralized equalization system obtains the advantages of high voltage gain, high efficiency, high reliability, and low cost, which is more attractive in engineering applications. Since different topology structures have various performances, a half-bridge-based ICB converter with a bidirectional switch is analyzed in detail as an example to validate the feasibility and effectiveness of the proposed topology family. The operation principles, design guidelines, and soft-switching conditions are discussed in more depth. Finally, the experimental results and comparative analysis are conducted to verify the advantages of the proposed ICB converter and prove the evident performance improvement compared with conventional methods.

Battery equalization management is a key technology to ensure the high-performance and safe operation of electrified transportation such as electric vehicles and electric aircraft. In this paper, an equalization current ripple cancellation (ECRC) converter for centralized equalization system is presented. Compared with traditional methods, the ECRC converter-based equalization system achieves a zero-ripple equalization current, so that the unfavorable influence of larger current pulsation on battery cells is eliminated. Meanwhile, under a phase-shifted PWM modulation strategy, the ECRC converter not only implements zero-voltage switching (ZVS) of all switches to reduce switching loss, but also decreases the peak current of the transformer to reduce transformer loss, so that the efficiency of the equalization system is significantly improved. Besides, the value of each power element in the converter is comparatively small, which is conducive to improving the power density of the centralized equalization system. To confirm the theory analysis, an experimental prototype based on a battery string containing 13 cells is built for experimental verification, and a systematic comparison is implemented with existing centralized equalization methods. The experimental and comparison results verify the design of the proposed equalization system and reflect the obvious performance improvement over traditional methods.

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.

Existing centralized equalization methods can only equalize one battery cell at a time, which is the main reason that limits the equalization speed and practicability of such methods. To overcome this limitation, this article proposes an integrated cascaded multiport converter (ICMPC) to optimize the structure and performance of the centralized equalization system. Through the proposed converter, the simultaneous and single-stage energy exchange between multiple unbalanced cells and the battery string can be achieved, so as to effectively improve the equalization speed. Meanwhile, the number of ports of the ICMPC is easy to expand, and the optimized system possesses the advantages of compact structure, high efficiency, and high cost effectiveness compared with conventional methods. As the basic and typical form of the ICMPC, the integrated cascade three-port converter is analyzed as an example in terms of operation principle, parameter design, and zero-voltage switching analysis. Finally, to confirm the theoretical analysis, a laboratory prototype is designed, and a comprehensive comparison is performed. The experimental and comparative results fully prove the practicality and superiority of the proposed ICMPC-based centralized equalization.