Research on Energy Equalization of Series Li-Ion Battery Pack Based on Multimodal Converter

Li-ion batteries are widely used in new energy vehicles and energy internet because of their superior charge/discharge performance and energy storage characteristics. In order to improve the energy difference of a single battery in a battery pack and enhance the chargeable and dischargeable capacity of the battery pack, a multimodal energy equalization circuit for series-connected battery packs is proposed in this paper. The circuit can achieve energy equalization between some battery packs as well as transfer energy from one overcharged battery to the rest of the batteries in the pack. In addition, a matrix equalization strategy is designed to be able to synchronize the two modes for equalization, and the performance of the equalization system is systematically considered. Finally, the system and the equalization time are compared through simulation and experimental verification. The experimental results show that the proposed multimodal equalization circuit and its control method can achieve fast equalization and the structure is easily scalable, which is expected to be applied to large-scale energy storage systems.