Test Bench Establishing And Nonlinear Modeling Of Lithium-ion Battery And Supercapacitor

With the implementation of energy conservation and emission reduction policies,the development and application of electric vehicles(EVs)have attracted wide attention.In order to meet the performance requirements of EVs' power system for the specific energy and specific power during driving,the power batteries and the supercapacitors form an improved hybrid system.In the design and state estimation of the energy management strategy of model-based hybrid power system,both battery models and supercapacitor models are of great importance.However,the classical model has a simple structure with its model parameters not updated in real time.Therefore,these models fail to describe the dynamic characteristics of lithium-ion batteries and supercapacitors,resulting in large errors in practical applications.To solve the above problems,this paper establishes a new type of lithium-ion battery model and supercapacitor model,and conducts in-depth research on the online parameter identification algorithm.The main research work is as follows:A battery test bench based on the ITS5300 has been designed.In order to ensure the accurate measurement results of the test bench,two basic parameters of voltage and current are accurately calibrated.Combined with the capacity requirements of lithiumion batteries and supercapacitors in the electric vehicle power system,the research object of this paper is determined as lithium-ion battery packs and supercapacitor modules;Research on the performance test of on lithium-ion battery packs and supercapacitor modules,provides a theoretical basis for the analysis of the features of energy storage components.Both lithium-ion battery packs and supercapacitor modules model are established.The working principle and charge-discharge characteristics of a single lithium-ion battery and a single supercapacitor are analyzed.These two models are analyzed,and a new type of equivalent circuit model that accurately reflects internal features of lithium-ion battery and supercapacitor is established.In addition,the relationship between a monolithic model and a group model is given a derived equation,and the group model for both lithium-ion batteries and supercapacitors are put in place.An online parameter identification algorithm based on extended Kalman filter is proposed.In the dynamic process of lithium-ion battery packs and supercapacitor modules,the online parameter identification algorithm is used to update and calibrate the model parameters in real time to maintain the model accuracy.The model parameters of the offline identification as the parameter initial value of the online parameter identification can reduce the parameter convergence time.With stimulation,the advantage of popularizing Kalman filter algorithm is verified.A test bench for a hybrid power system that hosts lithium-ion batteries and supercapacitors is built.The identification algorithm is embedded into the software of upper computer placed on the bench,and the online simulation experiment is performed on the identification algorithm.At the same time,the experiment on the actual working condition the electric vehicle is carried out on the test bench.The simulation data of the lithium-ion battery packs and supercapacitor modules model designed in this paper are compared with the test data of the test bench.The experimental results show that under UDDS conditions,the average relative error of both the lithium-ion battery packs model and supercapacitor modules model is within 1.61% and 2.14% respectively.This verifies the accuracy and effectiveness of the models and algorithm proposed in this paper.