A-modified-direct-torque-control-for-induction-mot

122IEEETRANSACTIONSONINDUSTRYAPPLICATIONS,VOL.36,NO.1,JANUARY/FEBRUARY2000AModifiedDirectTorqueControlforInductionMotorSensorlessDriveCristianLascu,IonBoldea,Fellow,IEEE,andFredeBlaabjerg,SeniorMember,IEEEAbstract—Directtorquecontrol(DTC)isknowntoproducequickandrobustresponseinacdrives.However,duringsteadystate,notabletorque,flux,andcurrentpulsationsoccur.Theyarereflectedinspeedestimation,speedresponse,andalsoinincreasedacousticalnoise.Thispaperintroducesanewdirecttorqueandfluxcontrolbasedonspace-vectormodulation(DTC-SVM)forinductionmotorsensorlessdrives.Itisabletoreducetheacous-ticalnoise,thetorque,flux,current,andspeedpulsationsduringsteadystate.TheDTCtransientmeritsarepreserved,whilebetterqualitysteady-stateperformanceisproducedinsensorlessimplementationforawidespeedrange.Thefluxandtorqueestimatorispresentedandanimprovedvoltage–currentmodelspeedobserverisintroduced.Theproposedcontroltopologies,simulations,implementationdata,andtestresultswithDTCandDTC-SVMaregivenanddiscussed.Itisconcludedthattheproposedcontroltopologyproducesbetterresultsforsteady-stateoperationthantheclassicalDTC.IndexTerms—Directtorquecontrol,estimators,sensorless.I.INTRODUCTIONRESEARCHinterestininductionmotor(IM)sensorlessdriveshasgrownsignificantlyoverthepastfewyearsduetosomeoftheiradvantages,suchasmechanicalrobustness,simpleconstruction,andmaintenance.Presenteffortsarede-votedtoimprovethesensorlessoperation,especiallyforlowspeedandtodeveloprobustcontrolstrategies.Sinceitsintroductionin1985,thedirecttorquecontrol(DTC)[1](ordirectselfcontrol(DSC)[2])principlewaswidelyusedforIMdriveswithfastdynamics.Despiteitssim-plicity,DTCisabletoproduceveryfasttorqueandfluxcontroland,ifthetorqueandfluxarecorrectlyestimated,isrobustwithrespecttomotorparametersandperturbations.However,duringsteady-stateoperation,notabletorque,flux,andcurrentpulsationsoccur.Theyarereflectedinspeedestimationandinincreasedacousticalnoise.PaperIPCSD99–46,presentedatthe1998IndustryApplicationsSocietyAn-nualMeeting,St.Louis,MO,October12–16,andapprovedforpublicationintheIEEETRANSACTIONSONINDUSTRYAPPLICATIONSbytheIndustrialDrivesCommitteeoftheIEEEIndustryApplicationsSociety.ThisworkwassupportedbytheDanfossProfessorProgrammeandtheInstituteofEnergyTechnology,AalborgUniversity,AalborgEast,Denmark.ManuscriptsubmittedforreviewOctober15,1998andreleasedforpublicationAugust23,1999.C.LascuiswiththeDepartmentofElectricalMachinesandDrives,UniversityPolitehnicaofTimisoara,RO-1900Timisoara,Romania(e-mail:[e-mail]).I.BoldeaiswiththeDepartmentofElectricalMachinesandDrives,UniversityPolitehnicaofTimisoara,RO-1900Timisoara,Romania(e-mail:[e-mail]).F.BlaabjergiswiththeInstituteofEnergyTechnology,AalborgUniversity,DK-9220AalborgEast,Denmark(e-mail:[e-mail]).PublisherItemIdentifierS0093-9994(00)00036-0.SeveralsolutionswithmodifiedDTCarepresentedinthelit-erature.Duetoitssimplestructure,DTCcanbeeasilyintegratedwithanartificialintelligencecontrolstrategy.Thefuzzylogicsolutionforfluxandtorquecontrolisshownin[3].Adifferentapproachistocombinethevoltagevectorselec-tionwithanadequatepulsewidthmodulation(PWM)strategyinordertoobtainasmoothoperation.Theclosed-loopstatorfluxpredictivecontrol,open-looptorquecontrolusingspace-vectormodulation(SVM)implementationisshownin[4].TheSVMisaperformantopen-loopvectormodulationstrategy[5].ThispaperintroducesanewdirecttorqueandfluxcontrolbasedonSVM(DTC-SVM)forIMsensorlessdrives.Itimple-mentsclosed-loopdigitalcontrolforbothfluxandtorqueinasimilarmannerasDTC,butthevoltageisproducedbyanSVMunit.Thisway,theDTCtransientperformanceandrobustnessarepreservedandthesteady-statetorquerippleisreduced.Ad-ditionally,theswitchingfrequencyisconstantandtotallycon-trollable.Anotherimportantissueforasensorlessdriveistheflux,torque,andspeedestimation.Bothopen-loopandclosed-loopspeedandpositionestimatorsarewidelyanalyzedinthelitera-ture.Themostpromisingspeedobserversseemtobetheadap-tiveones,eitherwithlinearornonlinearstructures[6],[7].How-ever,thelow-speedrangeestimationstillremainsanunsolvedproblem.Thisisnotthecaseforfluxandtorqueobserverswhichareabletogenerateaccurateestimationforthewholespeedrange[8]–[10].Animprovedvoltage–currentmodelspeedob-serverbasedonamodelreferenceadaptivecontroller(MRAC)structureisproposedherewith.ThepaperpresentsthecompletesensorlesssolutionbasedonaDTC-SVMstrategy.Theproposedcontroltopologies,digitalsimulations,implementationdata,andtestresultswithDTCandDTC-SVMaregivenanddiscussed.II.PROPOSEDSENSORLESSIMDRIVETheproposedsensorlessIMdriveblockdiagramisshowninFig.1.Itoperateswithconstantrotorflux,directstatorflux,andtorquecontrol.Thespeedcontrollerisaclassicalpropor-tional-integral-derivative(PID)regulator,whichproducesthereferencetorque.Onlythedc-linkvoltageandtwolinecurrentsaremeasured.TheIMmodelis(1)(2)0093–9994/00$10.00©2000IEEELASCUetal.:MODIFIEDDTCFORIMSENSORLESSDRIVE123Fig.1.TheDTC-SVMsensorlessacdrive.(3)(4)whereisthestatorvoltage,,arethestatorandrotorcur-rents,resepctively,arethestatorandrotorflux,respec-tively,arethemotorparameter