Research on active balancing scheme of lithium battery pack based on coupled winding

Aiming at the problem of energy inconsistency in the charging and discharging process of lithium battery packs, the traditional Buck-Boost equalization circuit and Flyback equalization circuit are used to balance the method. An active equalization circuit based on coupled windings, which can reduce circuit size, improve equalization speed and equalization efficiency, is proposed. By selectively charging and discharging the coupled windings, three different working modes realized energy transfer between the cells, and adjusted the duty cycle of the PWM drive signal to improve the working efficiency of the equalizer. In terms of the balance control strategy, according to the one-to-one correspondence between the open circuit voltage (OCV) of the lithium battery and the state of charge (SOC), a balance control strategy based on voltage and SOC dual variables was proposed, mainly through the rapid voltage balance and correction. The equalization and SOC equalization phases achieved both voltage equalization and SOC equalization, which ensures consistent dynamic performance of the battery pack. Experimental results show that the solution can reduce the equalization time of the battery pack, reduce energy loss, improve the equalization efficiency, and make the overall performance of the battery pack reach the optimal state. © 2021, Harbin University of Science and Technology Publication. All right reserved.