Research On Active Balance Technology Of Power Battery Pack Based On Multi-Transformer Method

Stacked lithium-ion battery packs are widely used in the field of electric vehicles and energy storage as energy storage and power output devices.However,due to various reasons,the problem of inconsistency among cells after the battery is grouped is outstanding.If not controlled,the inconsistency will continue to expand,which greatly affects the safety and performance of the battery.At present,the passive equalization technology of the battery pack is widely used,which has the disadvantages of small balance current,low efficiency,high energy consumption and the like,and can not achieve satisfactory effect on the power battery pack.In the field of power battery management system,active balancing technology of large current is urgently needed to complete the balancing of power battery.In order to solve these problems,the active balance technology of power battery is studied as follows:1)Lithium-ion battery characteristics and battery pack inconsistency analysis.Complex electrochemical reaction occurs inside the Batteries at work,the analysis of factors that affect the battery characteristics and battery inconsistency evaluation criteria,can better support the development of a balanced strategy.2)The overall scheme of active equalization module.The equalizer needs to select a topology that is easy to implement and suitable for active battery balancing.The design of the equalization module not only needs to match the corresponding peripheral circuits according to the equalization strategy,but also ensures that the distributed battery monitoring and control needs to be met.3)Research on the method to improve the estimation accuracy of State of Charge.State of Charge as an important equilibrium variable,the improvement of its estimation accuracy can improve the balance effect.Choosing a kind of estimation algorithm which is easy to implement on the embedded processor,how to further improve its estimation accuracy is also the content of this research.4)Research and implementation of active equalization control strategy.The traditional potential difference control scheme basically satisfies the use requirement for the passive equilibrium scheme of small current and the voltage fluctuation is obvious when multiple cells are balanced in active balancing.Simply using potential difference control can not guarantee the equalization effect.Therefore,an online equalization control strategy suitable for active balancing needs to be proposed to ensure equalization accuracy and convergence speed.In this paper,the equilibrium mode of power battery under different operating conditions is analyzed to further guide the formulation and implementation of the equalization control strategy.Finally,the battery balancing experiment is carried out on the basis of the active equalization module and the equalization control strategy.The balancing effect under different equalization control strategies is reproduced and compared.The balancing process and the balancing effect of the balancing strategy proposed in this paper are analyzed emphatically.Experiments show that the equalization module and equalization control strategy designed in this paper can work stably under different operating conditions to achieve a large current balance of power battery and ensure the consistency of the power battery.