Double-layer balance system of voltage source series energy storage battery pack for electric vehicles

Inconsistent material properties or structural composition of batteries may occur in the process of battery manufacturing, storage, and operation. The resulting inconsistency in the battery cells will make the series battery packs in electric vehicles have the hidden danger of accidents. This paper designs a two-layer combination balance system with fast speed and simple structure based on the analysis of graph theory. On the one hand, the system is based on a distributed topology to provide a direct energy transmission path for non-adjacent battery cells in the battery pack to fully improve the balancing speed. On the other hand, it takes full advantage of the fast speed of centralized topology to avoid the increase in control complexity caused by too many balancing paths. Finally, a suitable switching frequency and a balancing capacitor were selected based on the simulation experiment. The prototype of the double-layer combined balance system was designed and built to verify its faster speed and good effect.