电力电子 变频传动.docx

电力电子 变频传动.docx

《电力电子 变频传动.docx》由会员分享，可在线阅读，更多相关《电力电子 变频传动.docx（53页珍藏版）》请在冰豆网上搜索。

电力电子变频传动

ThomasM.Jahns

Chapter6

VariableFrequencyPermanentMagnetACMachineDrives

扫描:

林迪

识别:

核对:

李志强俞卫金雪峰薛梅

6.1Introduction

6.2PMACMachineControlFundamentals

6.3TrapezoidalPMACMachineControl

6.4SinusoidalPMACMachineControl

6.5AdvancedControlTechniques

6.6PmacDriveApplicationIssues

6.7Conclusion

References

6.1.INTRODUCTION

PermanentmagnetAC（PMAC）machinesprovideauniquesetofadvantagesandopportunitiestodesignersofmodernmotioncontrolsystems.PMACmachinescanbedesignedinmanydifferentgeometriesasdiscussedinChapter2,andafewcommonexamplesareillustratedinFigure6-1.TheuseofpermanentmagnetstogeneratesubstantialairgapmagneticfluxwithoutexternalexcitationmakesitpossibletodesignPMACmachineswithunsurpassedefficiencycharacteristics.Suchefficiencyadvantagesarebecomingincreasinglyvaluableinmanypartsoftheworldwheremarketforcesandgovernmentalmandatesarefocusingincreasedattentiononreducedenergyconsumptioninmanytypesofelectricalequipment.Forexample,minimumenergyefficiencyrequirementsaregraduallybeingimposedbytheU.S.governmentduringthe1990sonmajorclassesofresidentialappliancesaswellasheating,ventilating,andairconditioning（HVAC）equipment[1].

Alternatively,thelowlossesmadepossiblebytheappropriateapplicationofpermanentmagnetscanbeusedtoachievemachinedesignswithimpressivelyhighvaluesofpowerdensityandtorque-to-inertia（Te/J）ratios[2].ThesecharacteristicsmakePMACmachineshighlyattractiveformanyactuatorandservoapplicationsthatdemandthefastestpossibledynamicresponse.

Ontheotherhand,PMACmachinespresentspecialchallengestotheelectricalequipmentdesignersincetheyaresynchronousmachinesthat,intheabsenceofauxiliaryrotorwindings,absolutelyrequireaccompanyingpowerelectronicsforoperation.ThedriveelectronicsisnecessarytoperfectlysynchronizetheACexcitationfrequencywiththerotationalspeedasaprerequisiteforgeneratingusefulsteady-statetorque,incontrasttoaninductionmotorwhichtypicallyoperatesfromafixedfrequencyACsource（50or60Hz）.Asaresult,PMACmachinesareparticularlywellsuitedtomotioncontrolapplicationsthatcanjustifythecostofthepowerelectronicstotakeadvantageoftheuniquelyattractiveefficiencyanddynamicresponsecharacteristicsprovidedbythistypeofmachine.

Theobjectiveofthischapteristoreviewtheprincipalmotioncontroltechniquesthathavebeendevelopedsincethe1970sforPMACmachinedrives.TwomajorclassesofPMACmachines—trapezoidalandsinusoidal—wereintroducedinChapter2thathavesomenotabledifferencesintheirrespectivecontrolrequirementsandperformancecharacteristics.AmajorportionofthischapterwillbedevotedtoadiscussionofthecommonalitiesanddifferencesassociatedwiththecontrolofthesetwoimportantfamiliesofPMACmachines.ThespecialcontrolrequirementsofPMACmachinestoachieveextendedspeedoperatingrangesusingflux-weakeningtechniqueswillalsobeaddressed.

TheparticularrequirementsofPMACmachinesforsynchronizationoftheexcitationwaveformswithrotationalspeedhavegivenrisetoaconsiderablevarietyofcontroltechniquesforeliminatingtheshaft-mountedpositionsensorthatwillbereviewedlaterinthischapter.ThisdiscussionofadvanceddrivecontroltechniqueswillbefollowedbyacomparisonofthestrengthsandweaknessesofPMACmachinedrivescomparedtoothermajorcompetingmachinedrivetechnologies.ThechapterwillconcludewithsummarydescriptionsofseveralPMACmachinedrivesystemsthathavebeenselectedtoillustratethebreadthoffieldedapplications,leadingtoaclosingdiscussionofexpectedfuturetrends.

6.1.1.Background

PMACmachinedrivesrepresenttheconvergenceofatleasttwodistinctthreadsofpermanentmagnetmachinedevelopment.Oneofthesethreadsistheearlydevelopmentofline-startPMACmotorswithembeddedrotorsquirrelcagewindingsdesignedforoperationdirectlyfromutility-suppliedACpower.WorkonthisspecialclassofhybridPMACinductionmachinedatesbacktothe1950s[3,4]usingAlnicomagnets.Thesemachineswerewidelyappliedinsomeimportantindustrialapplicationssuchastextilemanufacturinglinesthatrequirelargenumbersofmachinesoperatingatidenticalspeeds[5].

Laterduringthe1970s,considerableresearchattentionwasfocusedonimproveddesignsforline-startPMACmachinesasameansofachievingsignificantenergysavingsinindustrialapplications.Integralhorsepowerversionsoftheseline-startPMACmotorshavebeendevelopedwithimpressiveefficiencycharacteristicsusingbothferriteandrare-earthmagnets[6],buttheirresultingmanufacturingcostpremiumsoverconventionalinductionmachinespreventedwidemarketacceptance.Nevertheless,significanttechnicalprogresshasbeendemonstratedinthedevelopmentofthesehigh-powerPMACmachines,andworkinthisareacontinuestoday[7].

Representingthesecondthreadofdevelopment,permanentmagnetDC（PMDC）servomotorsbegantodisplaceconventionalwound-fieldDCmotorsinhigh-performancemachinetoolservoapplicationsinthe1960swhensolid-stateDCchoppercircuitsreachedmarketmaturity[8].Theavailabilityofhigh-strengthrareearthpermanentmagnetsmadeitpossibletodevelopcompactfast-responsePMDCservomotors[9]withoutthesteady-statelossesandadditionalcircuitcomplicationsassociatedwithtraditionalwound-fieldDCmachines.

Finally,inthe1970s,thesetwodevelopmentpathsconvergedasPMACmachines（withoutrotorcages）werecombinedwithadjustablefrequencyinverterstoachievehigh-performancemotioncontrol[10].ThisapproachhadthedesirableeffectofeliminatingthedualdisadvantagesofhighrotorinertiaandbrushwearassociatedwithPMDCmotorcommutators.Theclassof"brushlessDCmotors"usingtrapezoidalPMACmotorswasdevelopedfirst[11]inordertotakeadvantageofthecontrolsimplificationsthatareachievablewiththisconfiguration,asdiscussedinmoredetailinSection6.3.Thishasbeenfollowedbytheevolutionofhigh-performancesinusoidalPMACmachinedrivesduringthelate1970sand1980swhichhavebeenmadepossiblebytherapidadvancesindigitalreal-timecontrolhardwareandvectorcontroltechnologyfirstappliedtoinductionmotors[12].

6.1.2.MotionControlPerformanceRequirements

AlthoughseveralofthebasicissuesassociatedwithmachinedrivespecificationswereintroducedinChapter2,afewkeypointswillbebrieflyreviewedhereinordertosetthestageforthefollowingdiscussionofPMACmachinecontroltechniques.Torque-speedenveloperequirementsforPMACmachinedrivestypicallyfallintooneoftwoclassesillustratedinFigure6-2."Constanttorque"applicationsarecharacterizedbythesquaretorque-speedenvelopeshowninFigure6-2awhichrequiresthatmaximumtorque

beavailableatallspeedsuptothemaximumrotorspeed

.Actuatorsandservosystemsaretypicalexamplesofconstanttorqueapplicationswhichrelyonmaximumtorqueavailabilityatallspeedstoensuremaximumdynamicresponse.PMACmachinesarenaturallywellsuitedforconstanttorqueapplicationsbecauseoftheconstantlevelofmagneticfluxdeliveredbytherotorpermanentmagnetstothemachine'sairgap.

Incontrast,"constanthorsepower"applicationsarecharacterizedbyatorque-speedenvelopewhichfollowsahyperbolicconstantpowertrajectory（Te-ωr=P0=constant）overawidespeedrangeabovebasespeedωbasillustratedinFigure6-2b.Oneofthemostfamiliarexamplesofaconstanthorsepowerapplicationiselectricvehicletractionthatrequireshightorqueforlow-speedaccelerationandreducedtorqueforhigh-speedcruising.ConstanthorsepoweroperationposesspecialchallengesforPMACmachinessincethereisnofieldwindingwhichcanbedirectlyweakenedasinaconventionalseparatelyexcitedDCmotor.However,"flux-weakening"controltechniquesareavailableforPMACmachinesthatcanachievethesameeffect,asdescribedlaterinthischapter.

Althoughtheprecedingdiscussionhasbeenframedintermsofsingle-quadrantmotoringoperationwithpositivetorqueandpositivespeed,manyapplicationsrequirethatthePMACmachinedevelopbrakingtorqueforcontrolleddecelerationandthatthemachinebeabletorotateinbothdirections.Suchrequirementsgiverisetotwo-andfour-quadranttorque-speedoperatingenvelopesasdiscussedpreviouslyinChapter2.ThePMACmachineiswellsuitedforsuchapplicationssinceitcanoperateequallywellasamotororgenerator,anddirectionofrotationhasnoimpactonthemachine'sperformancecharacteristics.

PMACmachinedriveapplicationscanbefurthercharacterizedfromacontrolstandpointbythenatureoftheprimarycontrolvariable.Thethreeprincipaltypesofdrivecontrolconfigurationsaretorquecontrol,speedcontrol,andpositioncontrol.Torquecontrolrepresentsthemostbasiccontrolrequirements,typifiedbytheacceleratorandbrakepedalsofanelectricvehicledrive.Manyotherindustrialandcommercialapplicationssuchaspumpsandprocesslinesrequirespeedcontrol,representinganintermediatelevelofcontrolperformancerequirements.Finally,positioncontrolsystemsgiverisetosomeofthemostdemandingmotioncontrolrequirementsforhigh-performanceapplicationssuchasmachinetoolservos.Motioncontrolperformancerequirementsarealsoreflectedindynamicresponsespecifications.Forexample,dynamicresponserequirementsforaPMACspeed-orposition-controlledservosystemaretypicallyexpressedintermsofbandwidthspecificationswhichdefinetheabilityofthedrive'soutputshafttofaithfullytracksinuso