Research On Internal Temperature Estimation Of Power Lithium Battery

In recent years,with the country's strong support for the electric vehicle industry,the electric vehicle industry has developed vigorously.As the main energy storage carrier of electric vehicles,power lithium batteries have been widely concerned.The safety problems caused by the thermal runaway of lithium batteries have gradually been paid more and more attention.The main reason for the risk of thermal runaway of lithium batteries is that the internal temperature and the external surface temperature show a high degree of inconsistency.As the discharge continues,this temperature difference is caused by the accumulation of larger and larger,and the battery pack is damaged and cannot work normally.In addition,there is a danger of explosion,which brings great safety risks to the user.In order to avoid the risk of thermal runaway of the lithium battery,the internal temperature of the lithium battery needs to be monitored and controlled in real time.When the lithium battery is in normal use,the external surface temperature can be directly measured by the sensor,and the internal temperature cannot be reasonably measured,Therefore,accurate estimation of the internal temperature of the lithium battery is the key to achieving safe and reliable thermal management of the battery.In view of the above issues,in this dissertation,the research on the internal temperature estimation of lithium batteries is carried out.Firstly,the temperature characteristics of the lithium battery are analyzed,and experiments related to the internal temperature change of the lithium battery are arranged,and the internal temperature and surface temperature changes of the battery are analyzed at different ambient temperatures,from the internal temperature and the surface temperature of the lithium battery.Starting from the difference,we will focus on the reasons for this difference,which will provide a reasonable basis for the following thermal modeling of lithium batteries.In order to accurately estimate the internal temperature of the lithium battery,it is particularly important to establish a more accurate lithium battery thermal model.In the establishment of the thermal model,the dissertation comprehensively considers various thermal factors and related theoretical knowledge bases.At the same time,the experimental data is used to optimize the existing lithium battery thermal model.Secondly,the identification error of each thermoelectric parameter in the battery thermalmodel is based on the influence of internal temperature estimation accuracy,a simplified variable parameter thermal model for lithium batteries was established.In addition,by identifying the internal heat capacity and external thermal resistance of the lithium battery at different ambient temperatures,a variable internal heat capacity and external thermal resistance estimation model is established to describe the influence of the external environment on the internal heat capacity and external thermal resistance,and through experiments verify the reliability of the model.The state space model is used to describe the lithium battery thermal model system,and a reasonable system dynamic equation and measurement equation are established.Considering the nonlinearity and complexity of the lithium battery thermal model system,combined with Extended Kalman Filter(EKF)algorithm,an internal temperature estimation method based on EKF is proposed.After establishing the internal temperature estimation algorithm,Further verified by experiments and simulations,the experimental results are proved to be applicable to the thermal model of lithium battery under different environmental temperatures,not only the internal temperature estimation is realized,but also the internal temperature estimation accuracy is improved.Finally,the previous article is summarized and the future research on the internal temperature of lithium batteries is directed.