Research On Equivalent Circuit Modeling And State Of Charge Estimation Of Lithium-ion Battery

As the world energy crisis and environmental pollution problems have become increasingly serious,governments have paid more and more attention to the research of electric vehicles which is zero emission and energy saving,making the new energy vehicles have become a hot topic of current research.Battery Management System as an important part of electric vehicles,through the effective control and management of vehicle power batteries,thereby ensuring the safe and reliable operation of electric vehicles.The accurate estimation of battery State Of Charge is one of the key technologies of the Battery Management System,and has been the focus and difficulty of the research all the time.For this reason,this paper had taken the lithium-ion battery as the research object,the battery model which influences the SOC estimation accuracy and SOC online estimation methods were studied in depth.This paper first introduced the background and significance of SOC estimation of lithium ion battery,The research status of SOC estimation at home and abroad was expounded,The internal structure and working principle of lithium ion battery were studied.The main factors influencing the performance of the battery were analyzed.The battery test platform was Built.A series of specific tests such as charge and discharge,open circuit voltage and Hybrid Pulse Power Characterization(HPPC)were carried out.The experimental data were analyzed and processed.Based on the experimental data,considering the accuracy of the model and the complexity of the algorithm,a two order RC equivalent circuit model was proposed to simulate the performance of the lithium-ion battery,Exponential fitting method was used to identify the dynamic parameters of the model.The validity of the model parameters was verified under the constant current and custom cycle current conditions.Based on the equivalent circuit model,the state space equation of the battery system was established,On the platform of Matlab/Simulink,The recursive estimation of SOC was realized using the Gauss-Hermite Quadrature Filter algorithm.The results show that the SOC estimation method proposed in this paper has high accuracy,Whether it is under the constant current,the periodic current,or the variable current working conditions,SOC can track the change of real value in real time.At the same time,the Gauss-Hermite Quadrature Filter(GHQF)algorithm has good robustness to SOC initial value,The speed of its convergence to the true value is fast.And SOC maximum error is not more than 3.7% in the whole estimation process,Withing high accuracy.