电气专业毕设英文文献(格式已修改)Word下载.docx
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DirectTorqueControlofInductionMotorsUtilizingThree-LevelVoltageSourceInverters
文献作者:
XavierdelToroGarcia,AntoniArias,MarcelG.JayneandPhilA.Witting
文献来源:
IEEETrans.Ind.Electron,vol.51,No.4,pp.744–757
发表日期:
2004年8月
班级:
姓名:
学号:
指导教师:
翻译日期:
英文原文:
DirectTorqueControlofInductionMotorsUtilizingThree-LevelVoltageSourceInverters
XavierdelToroGarcia,AntoniArias,MarcelG.Jayne,
andPhilA.Witting
Abstract—Anewcontrolstrategyforinductionmotorsbasedondirecttorquecontrolispresentedwhichemploysathree-levelinverterinsteadofthestandardtwo-levelinverter.Thecontrollerisdesignedtoachieveatorqueripplereductionbytakingadvantageoftheincreaseinthenumberofinverterstatesavailableinathree-levelinverter.Theharmonicdistortioninthestatorcurrentsandtheswitchingfrequencyofthesemi-conductordevicesarealsoreducedinthenewcontrolsystempresented.
IndexTerms—Inductionmotordrives,three-levelconverter,torquecontrol.
I.INTRODUCTION
Thestandardvoltagesourceinverter(VSI)traditionallyusedinelectricaldrivesystemsisthetwo-levelVSI,whichunfortunatelyhasanumberofinherentlimitations.Forexample,themaximumvoltagethatcanbesupportedbythesemiconductorswitchingdevicesintheVSIlimitsthemaximumvalueofdc-linkvoltage.Furthermore,theoutputvoltagesandcurrentsfromtheVSIcancontainhighharmonicdistortion.TheoutputvoltagewaveformscanalsocontainlargevaluesofdV/dt,whichcontributetothedegradationofthemachinewindingsinsulationandbearings,andalsoproduceconsiderableelectromag-neticinterferenceduringoperation.NewmultilevelVSItopologies,however,canconsiderablyreducemanyoftheselimitations[1].
Themostcommonlyusedmultileveltopologyisthethree-levelneutralpointclamped(NPC)VSI[2].ThistypeofVSIhasadvantagesoverthestandardtwo-levelVSI,suchasagreaternumberoflevelsintheoutputvoltagewaveforms,lessharmonicdistortion,andlowerswitchingfrequencies.
Directtorquecontrol(DTC)hasemergedtobecomeapossiblealternativetothewell-knownvectorcontrolstrategiesforinductionmotorcontrolsystems[3],[4].Althoughconsiderableresearchhasbeenmadeintothetwo-leveltopologiesassociatedwiththismethodofcontrol,theamountofresearchcarriedouttodateintoDTCsystemsemployingmultileveltopologiesisstillratherlimited.Themajoradvantageofthethree-levelVSItopologywhenappliedtoDTCistheincreaseinthenumberofvoltagevectorsavailable.Thismeansthenumberofpossibilitiesinthevectorselectionprocessisgreatlyincreasedandleadstoamoreaccuratecontrolsystem,whichcanresultinareductionofthetorqueandfluxripples.Thisisofcourseachievedattheexpenseofanincreaseinthecomplexityofthevectorselectionprocess.AlthoughseveralauthorshaverecentlyproposedtheimplementationofDTCutilizingthishigher-leveltopology,theirapproachesarebasedontheuseofmorecomplexvectorselectiontablescombinedwithmodulationtechniquesbasedonanalyticalmethodswhichhavemachineparameterdependency[5][6].Adifferentapproachisaselectiontablebasedontheconceptofvirtualvectors[7].ThesenewmethodsconsiderablyincreasethecomplexityofthecontrolstrategywhencomparedtotheclassicalDTCsystem[3],andtheycannotbeextendedtodifferentmultileveltopologieswithahighernumberoflevelsbecauseofthetableselectionmethodadopted.
Fig.1.Schematicdiagramofthenewcontroller.
ThispaperdescribesacontrollerbasedonDTCthatcanbeappliedtodifferentmultilevelVSItopologies.Itavoidstheuseofhysteresiscomparatorsandlook-uptables,anditdoesnotrequiretheknowledgeofthemotormodelinthecontrolsystemexceptfortheinherentestimatorasintheclassicalDTCsystem.
II.NEWCONTROLLER
ThegeneralstructureofthenewcontrollerisshowninFig.1.Thisnovelcontrollergeneratesareferencestatorvoltagevector(u∗s)inα–βcoordinates(usα,usβ)accordingtotheDTCbasicprinciple,ratherthanusingtheVSIstatelook-uptableasusedinclassicalDTC.ThisapproachadoptedisclosetotheDTCwithspacevectormodulationschemewithclosed-loopfluxandtorquecontrol,andstatorfluxorientedcontrol[4].Morerecently,othersimilarmethodsbasedonthepredictivetorquecontrolconcepthaveappeared[8][9].
Theinputstothecontrollerarethestatorfluxerror(eψs),thetorqueerror(eΓe)and,additionally,thestatorfluxangularspeed(ωB),whichisobtainedtoincorporatethebackelectromotiveforce(BEMF)termtoimprovethetorqueresponseatdifferentoperatingpoints.Thereferencevoltagevectorcalculatedbythecontrollercanbesynthesizedusingdifferenttechniqueswithdifferentdegreesofcomplexity,suchaschoosingthenearestvectoravailableorusingmodulationtechniques[9]–[11].ThiscontrollercanbeappliedtoanytopologybecausethetypeofVSIonlyaffectsthewaythereferencevoltagevectorhastobesynthesized.
Thecontrollerisbasedontheprinciplethatthedesireddecoupledcontrolofthestatorfluxmodulusandtorqueisachievedbythecontrolleractingontherespectiveradialandtangentialcomponentsofthestatorfluxvector(ψB).Thevariationofthestatorfluxvectorisapproximatelyproportionaltothevoltagevectorappliedtothemotor.Therefore,whencalculatingthereferencevoltagevector(inx–ycoordinatesfixedtothestatorfluxvector),thetangentialcomponent(u∗sy)willdependonthetorqueerror(eΓe),whereastheradialcomponent(u∗sx)willdependonthestatorfluxerror(eψB).AscanbeseeninFig.1,twoclosed-loopproportionalcontrollersareemployedtogeneratethecomponentsofthereferencevoltagevector.KψsandKΓearetheproportionalgainsofthesecontrollersandhavebeentunedexperimentallytoachieveaminimumtorqueandfluxripple.TheirinitialvaluescanbesettoapproximatelytheratiobetweennominalstatorvoltageandnominalstatorfluxmodulusforKψs,andtheratiobetweennominalstatorvoltageandnominalstatorflux
Fig.2.TorqueresponsecharacteristicsforclassicalDTCwithatwo-level
VSI.Operatingpoint:
Γ=7.4Nm.ωm=200r/min.
modulusforKψs,andtheratiobetweennominalstatorvoltageandnominaltorqueforKΓe.
ItcanbeseeninFig.1thatafeedforwardactionthatcompensatestheBEMFtermisaddedtotheoutputofthetorquecontrollertocalculatethetangentialcomponentofthereferencevoltagevector.TheBEMFtermisobtainedbymultiplyingthenominalstatorfluxmodulus(ψsn)andthestatorfluxangularspeed(ωs),whichispreviouslyfilteredbymeansofalow-passfilter.
Thereferencevectorinx–ycoordinatesisthentransformedtoα–βfixedcoordinates.ThenovelcontrollerdevelopedsynthesizesthereferencevoltagebychoosingthenearestVSIvectortothereferencevoltagevector.ThenearestvectorisfoundbymeansofcalculatingtheminimumdistanceofthevoltagevectorsthatcanbedeliveredbytheVSItothereferencevoltagevector.Thiscalculationinvolvesevaluatingthemodulusofthedifferencebetweenvectors.ThecomplexityofthesystempresentedisincreasedwhencomparedtoclassicalDTCduetotheuseofproportionalcontrollersinsteadofhysteresiscomparators,thex–ytoα–βcoordinatetransformationandthemethodtofindthenearestvector.Finally,itshouldbenotedthatthebalanceoftheneutralpointvoltageisoneofthemainissuesassociatedwiththecontrolofthethree-levelNPCVSI[11].InthenovelcontrollerthebalanceisachievedbyselectingtheappropriateconfigurationamongtheredundantpossibilitiesthatexistforsomeofthevectorsdeliveredbytheVSI.
III.EXPERIMENTALRESULTS
ThepracticalimplementationofthenewcontrollerisbasedonadSpaceDS1103boardthatperformsthecontroltasks.ThisboardcontainsaPowerPCandaDSP.Athree-levelNPCVSIutilizingIGBTdevicesisusedtosupplya380/220-Vfour-pole1.1-kWcage-rotorinductionmotor.Thedc-linkvoltageemployedis200V.Figs.2and3showthesteady-statetorqueresponsesat200r/minandnominaltorqueconditions(7.4Nm)fortheclassicalDTCstrategywithatwo-levelVSIandthenewcontrolsystememployingathree-levelVSIdescribedinthispaper,respectively.Thesampletimeusedwas100µ
sinbothsystems.
Toassesstheperformanceofbothsystems,thetorquestandarddeviation(σΓe)iscalculatedforthetorqueripple.Additionally,thefluxstandarddeviation(σψs),thetotalharmonicdistortion(THD)ofthestatorcurrentTHD_iS,andthemeanswitchingfrequencyinthesemiconductordevices(FSw)arecalculatedforbothsystems.FromtheexperimentalresultsshowninFigs.2and3,itisapparentthatthetorquerippleforthenewsystemutilizingathree-levelVSIisconsiderablyreduced.Theresult
Fig.3.Torqueresponsecharacteristicsforthenewcontrollerwithathree-levelVSI.Operatingpoint:
oftheVSIswitchesintheproposedsystemarebothreducedbymorethan50%.Theswitchingfrequencyisreducedduetotheutilizationofathree-levelVSI.InthistypeofVSI,sometransitionsbetweenthethreepossiblestatesofalegdonotinvolvethecommutationofalltheswitches.
IV.CONCLUSION
AnewcontrollerbasedontheDTCprincipleispresented,anditisshownthatthecontrollercanbeeasilyimplementedinathree-levelVSIdrivesystem.Thenewcontrollerdoesnotinvolvetheuseofanymotormodelparameters,asinclassicalDTC,andtherefore,thecontrolsystemismorerobustcomparedtoothermethodsthatincorporatemotorparameters.Theexperimentalresultsobt
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