In this paper, a high-efficiency and low-cost lithium-ion battery pack active balance system is designed. It adopts a distributed structure and consists of three parts: auxiliary power module, one-way isolated DC/DC conversion module, and a battery group. The battery single cells in the battery pack are layered and divided into m battery groups in total, and each battery group is composed of n battery single cells. Each battery group is connected to an isolated DC/DC conversion module, and all the conversion modules are connected in parallel with the auxiliary power. Taking the SOC average value of the all-single cells in one battery group as the balancing variable, the auxiliary power is controlled to charge the battery group with the lower SOC average value, so that the difference of the SOC average value of all battery groups is within the set threshold range, so as to realize the active balance of each battery group. For the single cells in the same battery group, by controlling the closing and opening of the bypass switch, the charging and resting of each single cell is realized, and finally the balance of the SOC of the single cells in the same group is realized.
This design adopts a layered and modular active balance topology, which is beneficial to improve the stability of the balance system and simplify the system structure. Multi-channel charging through the auxiliary power can balance multiple battery groups at the same time, reducing the loss of energy transmission and speeding up the active balance speed. Compared with the existing active balance topology, this design improves both economy and balance efficiency.