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Energies 2016,9, 563
6.BatteryModelsValidation
6.1. Evaluating theOpenCircuitVoltageModels (VOC)
Wijewardanaetal. [1]haveemployedacommonmodel forVOCthat iswidelyusedandfoundin
literature. LamandBauer [20]haveredefinedthemodelequation tosuit theLiFeMgPO4 cathodetype
batteries. Theyconcludedthat theOCVis temperature independent. They justifiedthisconclusion
basedonsmall changesof theOCVmeasurementsdueto temperaturevariations,whichwere in the
range2–8mV[20].Anabsoluteerrorof30mVforLiFeMgPO4batterycellwill leadtoanuncertaintyof
13%intheSOCestimationat1Cdischargeand25˝C,accordingtoBlanketal. [31]. Thebatteryofour
vehicle isLiFeMgPO4-cathodetype. ItsOCVcurvesarepresentedearlier inFigure6.Accordingtoour
measurements, theOCVtemperaturealterationisfrom15to90mV,whichisabout10timeshigherthan
theresultpresented inReference [20]. Inourstudy,weuseabatterymodule thatcontains6cellblocks
in series, with 50 cells in parallel for each. Moreover, the vehicle’s battery pack has 19modules.
With thiscombinationofbatterycells, therangeofvoltagealterationbecomes1.71–10.26V,which is
aconsiderablechange in thebatterypackoutputvoltage.
WevalidatedbothVOCmodels inReferences [1,20]bycomparing thesimulationresultswithour
ownmeasurements,asshowninFigure7.Weselectedthecharge-dischargecurvesatT=20˝Ctobe
thereferencesforvalidation. TheVOCmodelutilizedinbatterymodel3doesnotfitourmeasurements.
TheVOCofbatterymodel2betterfits theexperimentaldata. Thedeviation inanSOCrangespanning
from10%to90%isabout0.03V.Thisdeviation increasesat lowtemperature.
The influenceof the temperaturevariationontheOCVcurves isdefinedasdVOC{dT. Fromthe
measurementsshowninFigure6, thevalueof this termwasfoundtobe1.25mVincaseofdischarge
and0.69mVforcharging. TheVOCmodel2model ismodifiedforbetterfittingoftheOCVcurvealong
theSOCrangeandthe temperature influence is considered. ThenewVOC ismodeledbyEquations (8)
and(9)andtheconstantsvaluesof thenewVOCarepresentedinTable3. Thevalidationresultsare
showninFigure8andinTable4.
VOC,dischargepSOC,Tq“ a1 e´a2SOC`a3`a4 SOC`a5 e´ a6
1´SOC `TdVOC,d{dT (8)
VOC,chargepSOC,Tq“ b1 e´b2SOC`b3`b4 SOC`b5 e´ b6
1´SOC `TdVOC,c{dT (9)
Table3.VOCparametervalues.
Constant Value Constant Value
a1 ´1.166 b1 ´0.9135
a2 ´35 b2 ´35
a3 3.344 b3 3.484
a4 0.1102 b4 0.1102
a5 ´0.1718 b5 ´0.1718
a6 ´2ˆ10´3 b6 ´8ˆ10´3
dVOC,d/dT 0.00125 dVOC,c/dT 0.00069
6.2. Evaluating theBatteryModelsOutputVoltage
Theaccuracyof eachmodel isyet tobeproved. Forobjective comparison, the thermalmodel
elaborated inSection4 isemployedforallmodels. Thebatterycurrents inFigure6a,caredesignated
as the inputs forallmodelsandtheoutputvoltageofeachmodel is investigatedagainst thevoltage
response signal, shown inFigure6b,d. TheVOC ofmodel 3 [1] showeda largedeviation fromthe
actualcurve,asshowninFigure7. Therefore, theVOCderivedfrommodel2 [20]willbealsoutilized
inmodel 3. Figures 9 and10demonstrate the responses of the threemodels for bothdriving test.
Thesimulationresultsgainedfrommodel1 reveal thehighestaccuracy for thefirst test. Themean
133
Emerging Technologies for Electric and Hybrid Vehicles
- Titel
- Emerging Technologies for Electric and Hybrid Vehicles
- Herausgeber
- MDPI
- Ort
- Basel
- Datum
- 2017
- Sprache
- englisch
- Lizenz
- CC BY-NC-ND 4.0
- ISBN
- 978-3-03897-191-7
- Abmessungen
- 17.0 x 24.4 cm
- Seiten
- 376
- Schlagwörter
- electric vehicle, plug-in hybrid electric vehicle (PHEV), energy sources, energy management strategy, energy-storage system, charging technologies, control algorithms, battery, operating scenario, wireless power transfer (WPT)
- Kategorie
- Technik