Research On Active Equalization System Of Ternary Lithium Battery

With the vigorous development of the electric vehicle industry,the technological innovation and breakthrough of the power battery industry have been promoted.High-energy-density power batteries have emerged one after another,the high energy density advantage of the ternary lithium battery makes it a leader in the power battery market.However,the high energy density advantage of the ternary lithium battery is limited by the consistency between the cells in the battery pack,the inconsistencies in the voltage and capacity of the cells in the group which cause the cells in the group to be unfilled or not fully discharged when the charge and discharge are cut off,the available capacity of the battery pack is weakened.The inconsistency in the group will further deteriorate with the charging and discharging cycle,which will seriously cause early damage of the battery pack.This paper focuses on improving the consistency of the series battery pack,started from the sources of inconsistency in the group,expounded the research status of battery equalization technology,and determined that the consistency of the series battery pack is improved by the active equalization technology.Based on the analysis of the three elements of the equalization system,the SOC is used as the equilibrium index and the SOC acquisition method of this paper is established,the topology structure of any single-cell energy transfer-type equalization circuit based on the booster circuit is designed,the most valued equalization control strategy that takes rapid equilibrium and equilibrium temperature rise into account is designed.According to the equalization circuit topology,the sampling circuit and the equalization energy transfer circuit are designed.According to the equalization control strategy,The software design of the equalization system is completed.Finally,under the laboratory conditions,the parameter identification test of the first-order RC equivalent model of ternary lithium battery and SOC estimation accuracy calculation test were carried out.The 6-series ternary lithium battery pack was taken as the research object,Verification tests for the equalization effect of the static working condition and the discharging working condition were carried out.The test results show that the designed active equalization system can achieve rapid equalization in the series battery pack.