A Novel Modularization Method for Voltage Equalization of Ultracapacitor Bank Using Coupled Inductor

The voltage equalization of ultracapacitors (UCs) in a UC bank using coupled inductors is superior due to their advantages of simple control, fast energy transfer capabilities, etc. However, as the number of UCs connected in series or parallel in a UC bank increases, the number of windings on a single core required for balancing also increases. This causes severe mismatches between the inductance of the multiple winding in a single core, making the implementation more complex. Therefore, in this article, a novel modularization method is proposed for a matrix-connected UC bank. The proposed method achieves cell balancing, module balancing, and demagnetization with less number of components. Moreover, the proposed method uses a single pair of complementary pulsewidth modulation signals with a 50% duty ratio for all switches. The energy is transferred from the higher voltage cell to the lower voltage cell simultaneously through the coupled inductors, which increases the balancing speed. The balancing performance of the proposed modularization is validated experimentally.