Modular Equalization System Based on Star-Connected Phase-Shift Switched Capacitor Converters With Inherent Constant Current Characteristics for Electric Double-Layer Capacitor Modules

This article presents a modular equalization system integrating module- and cell-level voltage equalizers for energy storage systems consisting of series-connected modules, each comprising multiple cells connected in series. Star-connected phase-shift switched capacitor converters (PS-SCCs) and tapped-inductor-based resonant voltage multiplier (TI-RVM) are employed as a module- and cell-level equalizers, respectively. The module- and cell-level equalizers are integrated with sharing active switches, hence halving the total switch count and achieving reduced system cost and complexity in comparison with conventional systems. In addition, equalization currents in both the PS-SCC and TI-RVM can be inherently constant regardless of voltage imbalance conditions, offering intrinsic current limitation capability at both the module and cell levels. An experimental equalization test was performed using the prototype for five electric double-layer capacitor modules, each containing six cells connected in series. Module and cell voltages were equalized at different rates, and voltage imbalance was eventually eliminated even during cycling, demonstrating the equalization performance of the proposed modular equalization system.