An any-unit-to-any-unit method for hybrid-structured voltage equalizer in series-connected battery/super-capacitor strings

The slow balancing speed of switched-capacitor (SC)-based equalizers makes this structure difficult to apply in series-connected battery strings. In order to reduce the number of energy conversion processes and achieve leapfrog transmission of energy, a hybrid-structured voltage equalizer (HSVE) is developed in this work for battery strings to achieve high-speed any-unit-to-any-unit (AU2AU) equalization, in which each unit can also achieve internal balance in any arbitrary imbalance status. Compared to the conventional equalizers using complex monitoring and control strategy, the proposed equalizer does not need any cell monitoring circuits—all MOSFETs are triggered by a pair of complementary pulse signals with a fixed switching frequency and constant duty ratio, and electricity can automatically and directly exchange among all battery cells. Hardware experiments on super-capacitors and Li-ion batteries are conducted in this study, which prove the feasibility of the proposed voltage equalizer. The proposed battery management strategy will have wide applications in modern battery-related industries such as electric vehicles (EVs).