Modular Equalization System Based on Double-Layer Voltage Multipliers for Series-Connected Ultra-Capacitors String

Using a multi-winding transformer to drive voltage multipliers (VMs) for balancing ultra-capacitors (UCs) string can improve the scalability of the equalizer. However, each winding of the multi-winding transformer differs in the ratio of turns, leakage inductance, and bypass resistance, resulting in an imbalance between UC modules. Therefore, a modular equalization system based on double-layer VMs for series-connected UCs string is proposed, which uses VMs to balance the UC cells and modules, respectively. The converter’s energy transfer inductor acts as the voltage equalizer’s driver. An experimental charging test for two UC modules was performed. Cell and module voltages gradually became consistent.