A novel voltage equalizer using series/parallel switching capacitors

Electric Double Layer Capacitor (EDLC) is used as an electric energy storage device because it has large capacity. In the energy storage system composed of series-connected EDLCs, each cell has a different voltage because of the individual characteristic and of repeating charge and discharge. This difference of voltages deteriorates the performance of the whole storage system. In this paper, a novel voltage equalizer for series-connected EDLCs is proposed. By the circuit state which transfers the charge without EDLC, and by determining appropriate duty rate, the proposed circuit is able to equalize cell voltages faster than the conventional equalizer using Cockcroft/Walton circuit. The operation is analyzed with MATLAB/Simulink simulation.