Research On Multilayer Active Equalization System And Strategy Of Power Lithium Battery

Pure electric vehicles have developed extremely rapidly in recent years,becoming a research hotspot in the automotive industry.The advantages of lithium batteries over other storage batteries are obvious.Their long service life,high energy density,low self-discharge rate,and no memory effect are all the best choices for electric vehicles.However,lithium batteries are inconsistent during use.Sex also restricts its safety and life span,limiting its development.Therefore,the lithium battery pack equalization technology is particularly important in the battery equalization management system,and has important significance for the development of electric vehicles.This article first introduces some application trends of lithium batteries in the current market,and then explains its development status and policy support and guidance.Based on the reasons why the battery pack needs to be balanced,the causes of inconsistencies between lithium batteries are analyzed in detail,and how to resolve the inconsistencies.Then,several types of common battery equivalent circuit models are compared in depth,and related parameters of the second-order RC equivalent circuit model are identified.Secondly,four types of balanced topological circuits are analyzed:passive equalization,single-layer active equalization,double-layer active equalization,and multi-layer active equalization.Passive equalization mainly uses resistors as energy dissipating devices.The high-energy battery power is consumed through resistance to achieve the purpose of balancing.Active equalization mainly uses energy storage devices such as capacitors,inductors and transformers to transfer energy between batteries to achieve equilibrium purpose.This article mainly discusses the circuit structure,equalization strategy,application occasions,advantages and disadvantages.And thirdly,Taking the series lithium battery pack for electric vehicles as the research object,taking the equalization speed and equalization efficiency of the equalization system as the investigation results,based on the widely used Buck-Boost equalization circuit,two kinds of optimized multi-layer active equalization are proposed.Topology based on Buck-Boost and Fit capacitive multi-layer equalization circuits,the highest level uses Fit capacitor modules to replace the inductors in traditional circuits,which can achieve energy transfer between any batteries and improve the balancing speed and efficiency.Buck-Boost and transformer type Based on the traditional equalization circuit,the multi-layer equalization circuit optimizes the defect that each equalization sub-circuit can only transfer energy to adjacent cells,reduces the number of energy transfer steps in the cell equalization process,increases the equalization current,and thereby improves the equalization speed.Finally,the design of a multi-layer active equalization system is completed and simulated in MATLAB/Simulink.The simulation compares the traditional equalization circuit with the optimized equalization circuit in this paper.The analysis of the simulation image and the comparison of the data prove that the design in this paper The superiority of the layer active equalization circuit in the equalization effect and the equalization control strategy.Figure[56]Table[9]References[64]...