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Study On State-of-Charge Estimation Method Of Lithium-ion Battery For Battery Electric Vehicles

Posted on:2016-09-03Degree:MasterType:Thesis
Country:ChinaCandidate:J X ZhangFull Text:PDF
GTID:2272330467498657Subject:Control theory and control engineering
Abstract/Summary:PDF Full Text Request
With the rapid development of electric vehicles, people pay more and moreattention to the battery technology, in which, State of Charge (short for SOC) as a coreparameter of battery whose accurate estimation has become a hotspot and also a nodusof the research. In this paper, an accurate estimation of SOC for Lithium-ion battery(LIB) is the core research, and the main work of this paper is organized as follows:First of all, this paper introduces the development background of electric vehicles,and raises the significance of accurately estimating the SOC by introducing the mainfunction of battery management system (BMS). Paper summarizes the research statusof BMS, analyzes advantages and disadvantages of various common SOC estimationmethods, points out that for the lithium iron phosphate (LiFePO4) battery, theaccuracy of both battery model and algorithm performance is need to improved toimprove the accuracy and stability of the SOC estimation.By analyzing the classification and application of battery models, and combinewith the charge, discharge and rest characteristics of target battery, the second-orderThevenin equivalent circuit model (ECM) with hysteresis and variable parameters isselected as SOC estimation model. The relationship between SOC and open circuitvoltage (OCV), hysteresis voltage and model parameters for different currents isrespectively identified according to the experimental data. Finally, the higheraccuracy battery model is obtained.Subsequently, introduces the theory of Input-to-state stable (ISS) of system,proposes a LIB SOC estimation method based on ISS theory in order to overcome theproblem of estimation error divergence. By using LMI toolbox of Matlab solve the constant observer gain that maks system meets the ISS. Than build a nonlinearobserver in Simulink for the SOC estimation of the nonlinear battery model tosimulation experiment. The simulation results show that the nonlinear observer basedon the ISS framework can not only has faster convergence speed, but also guaranteethe accuracy of SOC estimation.Finally, matching parameters of battery module for AMESim electric vehicledemo, and executing co-simulation with Simulink. The further simulation resultsshow that the designed nonlinear observer is still able to accurately estimate the SOCof the battery pack in complex real operating conditions, and prove the stability andaccuracy of the observer.
Keywords/Search Tags:Li-ion battery, Equivalent Circuit Model, SOC Estimation, ISS, AMESim
PDF Full Text Request
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