A Series Resonant Energy Storage Cell Voltage Balancing Circuit

A novel cell voltage equalizer using a series LC resonant converter is proposed for series-connected energy storage devices, namely, battery or super (or ultra)-capacitor cells. The proposed circuit is an active voltage equalization circuit for energy storage devices that is low cost, small in size, and equalizes the voltages quickly. Compared to the state-of-the-art solutions, the proposed series LC resonant circuit eliminates the complexity of multiwinding transformers, and it can balance series-connected energy storage devices in a short time by transporting energy successively between the cells having highest voltage difference. The detailed circuit operation and theoretical analysis are provided. Simulation and experimental results are presented to demonstrate the voltage equalization process from an initial voltage difference of 527 mV to a final difference of 10 mV in 900 s for three series-connected supercapacitor cells.