Abstract：With the global energy transition and rapid growth of the electric vehicle (EV) market, the second-life utilization of retired power batteries has become a critical pathway for constructing new energy storage systems. However, retired batteries often face issues such as significant capacity degradation, increased internal resistance, and low capacity utilization in battery packs during their second-life application. These issues are particularly challenging in idle (non-charging/discharging) conditions, where conventional balancing methods exhibit technical limitations. Thus, this paper proposes a hierarchical balancing method based on a novel reconfigurable topology. Traditional reconfigurable topologies suffer from excessive switch numbers, reliance on DC-DC converters, and inadequate balancing under idle conditions. A new reconfigurable topology is introduced, adopting a hierarchical design featuring series/bypass connections between modules and split/parallel configurations within modules. Compared to conventional four-switch topologies, the proposed structure reduces the switch count by 12.5% and limits output voltage fluctuations to within 3% without additional DC-DC converters. Subsequently, a hierarchical coordinated balancing strategy is proposed. This approach synergistically couples asymmetric PWM energy scheduling among outer modules with intra-module cell-level management techniques, i.e., splitting, recombining, and bypassing—within inner modules. Specifically, asymmetric PWM is used to redistribute energy between outer modules, reducing SOC differences and preventing circulating currents during charging and discharging. Within the inner modules, a capacity gradient splitting and cell bypassing method is applied to optimize the SOC differences, ensuring balance across the entire battery pack. An RC circuit-based rapid balancing method is proposed for inner module balancing to overcome the limitations in balancing during idle periods of an energy storage system (ESS). The integration of the RC circuit with dynamic topology reconfiguration markedly amplified the inter-module voltage gradient, thereby expediting energy transfer between inner modules. Finally, a reconfigurable battery experimental platform is built. In discharge scenarios, experimental results show that the proposed strategy reduces the SOC difference from 6.65% to within 0.5% in approximately 1 000 seconds, with output voltage remaining stable and voltage fluctuations below 3%. Under ESS idle conditions, the RC circuit-based balancing strategy quickly reduces SOC differences between inner modules to below 0.5%, and peak currents are strictly controlled within safe limits. The proposed topology and balancing strategy are verified.
周娟, 郭泽赟, 杜世民, 张永磊, 庞宇凡. 基于新型可重构拓扑的电池分层均衡方法[J]. 电工技术学报, 2026, 41(6): 2132-2145.
Zhou Juan, Guo Zeyun, Du Shimin, Zhang Yonglei, Pang Yufan. A Hierarchical Balancing Method for Batteries Based on a Novel Reconfigurable Topology. Transactions of China Electrotechnical Society, 2026, 41(6): 2132-2145.
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