Research On Modeling And Equalization Management Of Power Lithium Battery Under The Influence Of Temperature

With the global energy crisis and environmental issues highlighted,the new energy technology revolution represented by electric vehicles has gradually become the commanding heights that all countries in the world compete for.As a complex electrochemical system,the highly non-linear and post-group consistency problems in the use of power batteries are the main factors that restrict the development of electric vehicles.Focusing on the frontier and hot issues in the field of battery management,this paper studies the two aspects of battery modeling and equilibrium management.By combining theory and experiment,the equivalent circuit model of lithium battery and the equilibrium simulation model of battery pack is built with the aid of modern computer simulation and data processing technology,aiming at improving the precision of the lithium battery model and optimizing the equilibrium strategy.In this paper,A123 lithium battery is taken as an example to analyze the relationship between temperature,open circuit voltage,capacity,coulomb efficiency,and internal resistance through the characteristic tests under different temperatures.The changes of the above parameters at different temperatures are summarized to guide the battery modeling.In view of the influence of hysteresis on the estimation of SOC,the hysteresis error in different intervals is analyzed.It is pointed out that the modeling of lithium battery can't ignore the effect of hysteresis.By comparing the hysteresis voltage distribution at different temperatures,the law of exponential decay with increasing temperature and the decay speed is affected by the SOC is summarized.The equivalent hysteresis model of lithium battery is further proposed.The open circuit voltage and internal resistance of the model are analyzed using the constant current with a small rate and the standard city cycle conditions respectively.Finally,a battery model considering the thermal effect is build using Simulink and it is verified that the battery model error can be reduced by half if the hysteresis is considered.Focusing on the issue of battery balance management,research is conducted from the following three aspects: analysis of consistency differences,design of balance circuits,and formulation of balanced strategies.First of all,the causes of the unbalance of battery pack is analyzed from the point of manufacturing and later usage.Secondly,a point to point equilibrium circuit based on the power inductance is proposed by the comparative analysis on common equilibrium topology.Then the parameters of the circuit are verified by the Pspice.Finally,the research on the equalization strategy starts from the selection of equilibrium basis,the design of equalization algorithm and the control of equalization sequence.In this paper,the SOC is taken as the equilibrium basis and the fuzzy logical algorithm is used to control the equilibrium current.Efficiency based on maximum-minimum and group-based equilibrium time series is verified in the static,constant current charging and DST conditions respectively.