An Enhanced Coupled Inductor Based Voltage Equalizer for Matrix Connected Ultracapacitor Bank

This article proposes an automatic any-cell-to-any-cell voltage equalization of matrix-connected ultracapacitor (UC) strings with a coupled inductor as a medium to transfer energy. The proposed equalizer reduces the number of switches and inductor winding in the balancing circuit and significantly speeds up the equalization process due to the matrix arrangement. The proposed balancing circuit requires a single pair of complementary pulsewidth modulation (PWM) signals with a 50% duty ratio to balance the whole UC bank. As a result, control complexities are greatly reduced compared to conventional active voltage balancing approaches, ensuring improved reliability and easier implementation. The proposed method is validated experimentally using 1 and 360 F UC strings.