Research on dynamic voltage equalization circuit for series connected ultracapacitors

This paper presents a novel circuit for equalizing a series ultracapacitor stack based on DC-DC converter. The proposed voltage equalization circuit derives energy from the series ultracapacitor stack and transfers them to the weakest ultracapacitor cell. The equalizer balances the whole stack by compensating the weak ultracapacitor cells sequentially. Unlike previous methods, which include complex circuit detecting and comparing the voltages of capacitor cells, the novel equalizer can realize autonomic voltage equalization without voltage detection and comparison.