Modularized Delta Switched-Capacitor Voltage Balancing Circuit with Series-Parallel Configuration for Series-Connected Battery Systems

Voltage imbalances in series-connected batteries significantly degrade battery performance, reduce battery lifespan, and pose critical safety risks, presenting substantial challenges for effective battery management systems (BMS). Switched-capacitor (SC) based-voltage balancing methods have been extensively studied due to their compact design, straightforward control, and cost-effective implementation. However, these methods are often limited by slow balancing speeds. Various SC circuit structures have been proposed to address this issue, with the delta structure SC showing promise in enhancing balancing speed. Nevertheless, this structure requires a large number of capacitors in tiers, leading to increased circuit complexity, making it impractical for systems with a large number of series-connected battery cells. Conventional modularization approaches also fall short in effectively managing certain imbalance scenarios. In response, this research introduces a novel modularization of the delta structure SC aimed at improving balancing speed. Simulations on five imbalance cases were conducted on a system comprising five battery modules, each containing four series-connected cells. The results demonstrate that the proposed system can double the balancing speed compared to conventional modularization of the delta structure SC. Furthermore, the proposed modularization is straightforward in its practical implementation, making it particularly suitable for electric vehicle (EV) applications that require a large number of series-connected battery cells.