外文翻译电动汽车外转子定子PM无刷电机驱动器的比较.docx

外文翻译电动汽车外转子定子PM无刷电机驱动器的比较.docx

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外文翻译电动汽车外转子定子PM无刷电机驱动器的比较

外文原文

ComparisonofOuter-RotorStator-Permanent-MagnetBrushlessMotorDrivesforElectricVehicles

K.T.Chau1,SeniormemberIEEE,ChunhuaLiu1,andJ.Z.Jiang21DepartmentofElectricalandElectronicEngineering,TheUniversityofHongKong,HongKong,China

2DepartmentofAutomation,ShanghaiUniversity,Shanghai,200072,China

Abstract—Inthispaper,twoemergingouter-rotorstator-permanent-magnet（PM）brushlessmotordrives,namelythedoubly-salientPMmotordriveandthePMhybridbrushlessmotordrive,arefirstlyquantitativelycompared,whichareparticularlyattractiveforservingasin-wheelmotordrivesforelectricvehicles.Inordertoenableafaircomparison,thesetwomotordrivesaredesignedwiththesameperipheraldimensionsandbasedonthesameouter-rotor36/24-poletopology.Byutilizingthecircuit-field-torquetime-steppingfiniteelementmethodforanalysis,theirsteady-stateandtransientperformancesarecriticallycompared.Moreover,thecostanalysisofthesetwomachinesisconductedtoevaluatetheircosteffectiveness.

IndexTerms—Electricvehicle,Finiteelementmethod,Machinedesign,Permanent-magnetmotordrive.

I.INTRODUCTION

Inrecentyears,permanent-magnet（PM）brushlessmotordriveshavebeenwidelyusedinelectricvehicles（EVs）[1-2].Thedoubly-salientPM（DSPM）motordriveandPMhybridbrushless（PMHB）motordrivearetwoemergingstator-PMbrushlessmotordriveswhichofferhighmechanicalintegrityandhighpowerdensity,hencesuitableforEVapplications[3].Theirouter-rotormotorstructuresareparticularlyattractivefordirectdrivingofEVs,especiallyforservingasin-wheelmotordrivesforEVs[4].However,aquantitativecomparisonofthesewomotordrivesisabsentinliterature.

Thepurposeofthispaperistonewlycomparetwoemergingouter-rotorstator-PMbrushlessmotordrives,namelytheDSPMandPMHBtypes.Basedonthesameperipheraldimensions,bothmotordrivesaredesignedwiththeidenticalouter-rotor36/24-poletopology.Byusingthecircuit-field-torquetime-steppingfiniteelementmethod（CFT-TS-FEM）[5],thesteady-stateandtransientperformancesofbothmotordrivesarecomparedandanalyzed.Moreover,thecorrespondingcosteffectivenesswillberevealedanddiscussed.

SectionIIwillintroducethemotordrivesystemsandtheirconfigurations.InSectionIII,thedesignandcosteffectivenessoftwomotordriveswillbecompared.SectionIVwilldiscusstheanalysisapproachofthesetwomotordrives.ThecomparisonoftheirperformanceswillbegiveninSectionV.Finally,aconclusionwillbedrawninSectionVI.

II.SYSTEMCONFIGURATIONANDOPERATIONMODESFig.1showstheschemesofthesetwoouter-rotorstator-PMmotordriveswhentheyserveasthein-wheelmotordrivesforEVs,especiallyformotorcycles.Itcanbeseenthatthesein-wheelmotordriveseffectivelyutilizetheouter-rotornatureanddirectlycouplewiththetirerims.So,thesetopologiescanfullyutilizethespaceandmaterialsofthemotordrives,hencegreatlyreducingthesizeandweightforEVapplications.

Fig.1.Topologiesofproposedin-wheelmotordrives.（a）DSPM.（b）PMHB

ThetwomotordrivesconfigurationsareshowninFigs.2and3.Itcanbefoundthattheyhavethesimilarthree-phasefullbridgedriverforthearmaturewindings;whilethedifferenceistheH-bridgedriverfortheDCfieldwindingsofthePMHBmotordrive.Hence,theiroperationprinciplesareverysimilar,exceptthatthecontrollablefieldcurrentofthePMHBmotordrive.Forbothmotordrives,whentheair-gapfluxlinkageincreaseswiththerotorangle,apositivecurrentisappliedtothearmaturewindings,resultinginapositivetorque.Whenthefluxlinkagedecreases,anegativecurrentisapplied,alsoresultinginapositivetorque.ForthePMHBmotordrive,itcanaccomplishonlinefluxregulationbytuningthebidirectionalDCfieldcurrent.

Whenthesetwomotordrivesactasin-wheelmotordrivesandareinstalledintheEVs,theyoperateatthreemodeswithinthespeedrangeof0~1000rpm,namelythestarting,thecruising,andthecharging.

•WhentheEVoperatesatthestartingmode,itneedsahightorqueforlaunchingoracceleratingwithinashorttime.FortheDSPMmotordrive,sinceitsPMvolumeismuchmorethanthatofPMHBmotorone,itcanprovideasufficientlyhightorquefortheEVstarting.ForthePMHBmotordrive,thepositiveDCfieldcurrentwillbeaddedtoproducethemagneticfieldtogetherwiththePMexcitedfield,henceitalsoabletoofferthehightorquefortheEVtoovercomethestartingresistanceandthefrictionforceontheroad.

•WhentheEVrunsdownhillorworksinbrakingcondition,itworksinthechargingmode.Inthismode,thesetwomachinescanplaytheroleofelectromechanicalenergyconversion,whichrecoverorregeneratethebrakingenergytorechargethebatterymodule.Furthermore,forthePMHBmachinedrive,itcanfullyutilizeitsfluxcontrollableabilitytomaintaintheconstantoutputvoltagefordirectlychargingthebattery,whichismoreflexiblethantheDSPMmachinedrive.

•WhentheEVrunsinthecruisingmodeorinthesteadyspeed,thesestator-PMmotordriveswillentertheconstant-powerregion.Thisspeedrangeusuallycovers400rpm~1000rpmfortheDSPMin-wheelmotordrive.ButforthePMHBmotordrive,itnotonlycaneffectivelyextenditsoperatingspeedrangeupto4000rpmwhichisenoughtocovertheconventionalspeedrangerequirement,butalsocanregulateitsmagneticfieldsituationwhichcanmakethepowermoduleworkingattheoptimaloperationpoint.

Fig.2.ConfigurationofDSPMmotordrives.

Fig.3.ConfigurationofPMHBmotordrive.

III.COMPARISONOFMOTORDRIVESSTRUCTURESANDFEATURES

Thetwostator-PMmotordrivesstructuresareshowninFigs.2and3.Itcanbeseenthattheyhavethesameperipheraldimensionsandtheidenticalouterrotor,aswellasthesame36/24poleandarmaturewindings.Themajordifferenceistheirstatorsandfieldexcitations.TheDSPMmotordriveissimplyexcitedbyPMs,whichislocatedinthestator.ButforthePMHBmotordrive,ithasdouble-layerstatoranddoubleexcitations.Itsouter-layerstatoraccommodatesthearmaturewindings,whereasitsinner-layerstatorcontainsPMsandDCfieldwindingstogethertoproducethemagneticfield[6].Theirsimilarstructuresachievemanyadvantageswhentheyserveasthein-wheelmotordrivesforEVs.

•Theouter-rotornaturecanmakethemachinedirectlyconnectwiththetirerim,whichtotallyeliminatesthemechanicalgeartransmissionandprocesseshighmechanicalintegrity.Hence,itreducesthepowerloss,thesystemcomplication,andthetotalcost.

•Thesemotordrivesfullyutilizethewholespace,whichmakesthemcompactandeffective.Theyarrangethestatortolocatethewindingsandexcitations,henceresultingintherobustouterrotor.

•Theconcentratedarmaturewindingswith36/24fractional-slotstructurecanshortenthemagneticfluxpathandthespanofend-windings,whichleadtoreducebothironandcoppermaterials.Moreover,thisarrangementofwindingscansignificantlyreducethecoggingtorquewhichusuallyoccursatconventionalPMmotordrives.Theirdifferentconstructionsalsomakethemhavedistinctfeatures.

•FortheDSPMmotordrive,ithassimplerstructurethanthePMHBone.Alsoitscontrolstrategyissimpler.Butthissimplestructurelimitsitsflexibilityduetoitsuncontrollableairgapflux.

•ForthePMHBmotordrive,sinceitfullytakesadvantageofdoubleexcitations（bothPMsandDCfieldwindings）,itcanofferflexibleairgapfluxcontrol,includingfluxstrengtheningorweakening.Inaddition,theair-bridgeispresenttoshuntwitheachPM,henceamplifyingtheflux

weakeningability.Thecorrespondingfieldexcitationinevitablycausesadditionalpowerloss.Nevertheless,thisreductionofefficiencycanbepartiallycompensatedbytheefficiencyimprovementduetoairgapfluxcontrol.Byproperlytuningtheairgapfluxdensity,theefficiencycanbeonlineoptimizedatdifferentspeedsandloads.

Fig.4.Controlstrategies.（a）DSPM.（b）PMHB.

Fig.4showsthecontrolstrategiesofthesetwostator-PMmotordrives,indicatingthatthePMHBmotordrivehasanadditionalfluxcontrollertoregulatetheairgapflux.

ThepoleselectionoftheDSPMmotordriveisgovernedbythefollowingequations:

Ns=2mkandNr=Ns-2k

（1）

wheremisthenumberofphases,ktheinteger,Nsthenumberofstatorpoles,andNr

thenumberofrotorpoles.ThepoleselectionofthePMHBmotordriveisgivenby:

＝4mpand

＝2Ns/m

（2）

wherepisthenumberofpolepairsoftheDCfieldwindings.Therefore,whenthesuitableparametersareselected,namelym=3,p=3,andk=6,thepolesofthesestator-PMmotor

drivesleadtobe

＝36，and

＝24.Itcanbefoundthatfor

three-phasearmaturewindingsofthePMHBmotordrive,alltheotherparameterscanbeobtainedaccordingtothevalueofp.Hence,theaforementionedequation

（2）canbeusedtosimplydeterminetheotherpossibleslot-toothcombinationforthePMHBmotordrive.

IV.ANALYSISAPPROACH

TheCFT-TS-FEMcanbeusedtoanalyzethesteady-stateandransientperformancesofbothmachinedrives.Foreachmachinedrive,themathematicmodelconsistsofthreesetsofequations:

theelectromagneticfieldequationofthemachine,thecircuitequationofthearmaturewindings,andthemotionequationofthemotordrive.Theelectromagneticfieldequationofbothmachinedrivesisgivenby[7]:

whereΩisthefieldsolutionregion,vthereluctivity,σtheelectricalconductivity,Jthecurrentdensity,Athemagneticvectorpotentialcomponentalongthezaxis,and

and

thePMremanentfluxdensitycom