Study On Thermal Analysis And Temperature Control Of Electric Vehicle Battery Pack

In the new development period,energy issues and environmental protection issues have received extensive attention.With the advent of the era of electrification,the development of electric vehicles is experiencing a rapid rise.The advantages of environmental protection,energy saving and high energy utilization rate of electric vehicles themselves make them well adapted to the needs of sustainable development and environmental protection,but their safety performance needs to be improved.Lithium-ion batteries have higher energy density and lower self-discharge ratio,and have been widely used in electric vehicles.Lithium-ion batteries can only perform their performance if they work within a suitable temperature range(generally 15 °C to 38 ° C),otherwise their capacity and life will be reduced.Excessive heat generated by the battery will make it out of control,and in severe cases,it may cause dangerous accidents such as spontaneous combustion or even explosion.Therefore,it is of great significance to conduct thermal analysis and temperature optimization control research.Based on the above situation,the main research contents of this article are as follows:Make a brief introduction to the background and significance of the research of this topic,summarize and compare the current thermal analysis models commonly used in batteries,and introduce and analyze the current research status of temperature optimization control.The composition and working principle of the lithium ion battery,as well as the heat generation mechanism during the charge and discharge of the lithium ion battery and the heat transfer characteristics between the battery and the outside air are analyzed.By comparing and analyzing several equivalent circuit models that the heat production process relies on,a second-order RC model was selected to calculate the heat production of the battery pack.Through charging and discharging experiments,the parameters of the second-order RC model were identified and applied to the Simulink model built subsequently.According to the Bernardi heat generation rate model and Newton's cooling law,a thermal analysis model can be built in MATLAB / Simulink that can provide real-time feedback on temperature and SOC(state of charge).The genetic algorithm is used to optimize the thermal physical parameters.The standard deviation of the simulated temperature and the experimental temperature under the NEDC operating conditions is less than 0.5 ?,which ensures the accuracy of the thermal analysis model.The influence of different factors on thetemperature of the battery pack is analyzed and verified,and it is verified that the convection heat dissipation coefficient,the ambient temperature and the charge and discharge rate have a relatively obvious influence on the battery temperature.On the basis of the established thermal analysis model,a temperature optimization control module based on PID was further added to Simulink,so that the temperature could reach the target temperature value,and a reasonable optimization process for the temperature was realized.In order to solve the difficulty of PID parameter setting under different conditions and needs,the PID parameters are obtained through genetic algorithm optimization to achieve optimal control of the temperature of the battery pack under different working conditions and needs.It has certain reference significance for the design of the actual thermal management system of the electric vehicle battery pack.