| Nowadays due to the increase of global warming decreasing of oil,fossil fuels,the Electric vehicles（EV）have become more popular and the use of EVs receive massive need cause of their performances and efficiencies in last years.EVs have been already accepted in the automotive industries considering the most promising replacement in reducing CO2 emissions in a global environment.Usage of lithium-ion batteries has huge attention in EVs application due to their beneficial features such us lightweight,fast charge,high energy density and long life span.In this thesis,a lithium-ion battery cell is analyzed and modelled on Matlab.The electrical performance of lithium-ion battery is considered.Developing a model of performance which accounts for the current rating and state of charge（SOC）helps to analyze the behavior of the cell under load.Different approaches of modelling lithium-ion battery cells are proposed in many kinds of literatures,physics-based electrochemical model and electrical models are the most discussed topics.In this work electrical model is designed and simulated for various working conditions.The model has a variable voltage source which accounts the open-circuit voltage（OCV）as a function of state of charge,a series resistor to account the instantaneous voltage change,when the cell is under load or relaxed,and parallel resistor and capacitor（RC）branches to capture the dynamics of the cell during the operation.The battery cell is operated under different current rates and state of charge,and data is recorded for impedance parameters identification.Curve fitting techniques are applied to determine the values of RC branches.Two RC branches are chosen to the battery model and the Curve fitting tool on Simulink optimization toolbox is used to identify the parameters（resistor ad capacitor as a function of the current rate and SOC）.The estimated values are highly nonlinear and represented in the model by the 2D lookup tables with linear interpolation.Coulomb counting method is applied to determine the true SOC,which considers the maximum capacity of the cell.OCV is modelled in terms of 2D lookup table,as a function of SOC from measurement data parameters using the HPPC test result.The errors in the terminal voltage are estimated and counted in SMO and EKF algorithm for the estimation of SOC.Once the impedance parameters and errors are estimated,the model is validated by a constant current discharge test and UDDS tests. |
