SOC Oriented Electrochemical-thermal Coupled Modeling For Lithium-ion Battery

With the deepening of the energy crisis and the serious pollution problems,electric vehicles have become a new star in the automotive industry due to their energy-saving and high efficiency.The power performance,stability and safety of electric vehicles depend on the performance of the power battery.Among the power batteries,the best performance and the most potential are the lithium-ion batteries.Therefore,it is very important to monitor the lithium-ion power battery in real time.This requires the internal state quantities of the battery,such as SOC and SOH.If you want real-time,colleges and universities to accurately obtain these quantities,you must have an accurate battery model.Therefore,establishing a precise battery model for a lithium ion battery and designing a corresponding internal state quantity estimation algorithm is crucial for the safe and stable operation of an electric vehicle.The main research contents of this article are as follows:The working mechanism of lithium-ion batteries was analyzed.Firstly,the commonly used electrochemical model-quasi-two-dimensional model of the battery was introduced,and two numerical problems of the quasi-two-dimensional model were analyzed: too many states due to dimensions,and hyperbolic sine The nonlinearity leads to high computational complexity.Furthermore,the problems that the two-dimensional model focuses on in this paper are solved separately.First,the two-dimensional model is reduced in dimension,a one-dimensional model is built,and the Padé approximation is further used for simplification.Finally,a simplified one-dimensional model is proposed..Then based on Matlab / Simulink simulation and Fortran program,the accuracy of the model was verified,and the cause of the error was also analyzed,namely the neglect of the change of lithium ion concentration in the liquid phase and the parameter error.Based on the simplified one-dimensional model,considering the influence of temperature,an electrochemical-thermal coupling model was established to first analyze the principle of heat generation of the battery and the principle of heat exchange of the battery.Based on this,the equation based on Bernardi was built.The lumped-mass thermal model ofthe battery with Newtonian cooling principle was then introduced into the internal parameters of the battery following the relationship of Arrhenius equations,and the electrochemical-thermal coupling model of the lithium ion battery was finally established,using the improved Fortran language program.The two-dimensional model-considering the quasi-two-dimensional model of temperature as a reference value,verified the accuracy of the constructed electrochemical-thermal coupling model from both terminal voltage and temperature.Finally,based on the electrochemical-thermal coupling model,the SOC estimator was designed.Firstly,the characteristics of the electrochemical-thermal coupling model were analyzed.Then the estimation problem based on the coupling model was analyzed,and the self-adaptation based on the electrochemical-thermal coupling model was designed.The SOC observer then performs Lyapunov analysis on the asymptotic convergence of each estimator,and then gives a general method for selecting the observer gain.Finally,using the Fortran program as a battery,the proposed adaptive observer is verified.The result shows that the observer has higher estimation accuracy.The main contributions of this paper are: First,two numerical problems of the quasi-two-dimensional model are solved,and a simplified one-dimensional model with high accuracy and high computation efficiency is proposed.Second,on the basis of simplification of the one-dimensional model,an electrochemical system is constructed.-Thermal coupling model,taking into account temperature factors,and improved simulation of Fortran language programs.Third,based on the electrochemical-thermal coupling model,an SOC adaptive estimator was designed.