Research on Active Equalization System of Power Battery

Abstract

A hierarchical active equalization topology based on Cuk converter and flyback converter was proposed to solve the problem of the inconsistency of series battery packs used in electric vehicle power cells. Using state of charge (SOC) as equalization standard, two equalization control strategies were developed, the second-order equivalent circuit model of lithium ion battery and open circuit voltage (OCV) characteristic curve were established to identify parameters and estimate SOC. The equalization of single battery in series battery was realized, and the inconsistency of series battery was reduced. Finally, a balanced experimental platform was built for verification. The layered active equalization framework gives full play to the advantages of the two kinds of active equalization, and improves the problem of the inconsistencies of the series battery. According to the SOC distribution of all the single cells in the series battery, the balancing control strategy is selected, which can effectively shorten the balancing time.