直流无刷电机外文资料原文及译文.docx
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直流无刷电机外文资料原文及译文.docx
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直流无刷电机外文资料原文及译文
外文资料原文
CommutationTorqueRippleReductioninBLDCMotorUsingPWM_ON_PWMMode
GuangweiMeng,HaoXiong,HuaishuLiDepartmentofElectricalEngineering,NavalUniversityofEngineering,Wuhan,China.
Abstract--ThepaperanalyzesthesteadycommutationprocessoftheBLDCmotorusingPWMmode,confirmsthecommutationtimetokeepnoncommutationphasecurrentamplitudeconstantduringcommutationperiodbywayofPWMintheperiodtoimplementthecompensationcontroltoeliminatecommutationtorquerippleunderbothlowspeedandhighspeedoperation,investigatestheeffectbyPWMmodeonathree-phasesix-state120°turn-onBLDCmotor,andpresentstorqueripplecompensationcontrolinPWM_ON_PWMmode,whichcannotonlyentirelyeliminatetorquerippleresultedfromthecurrentemergingintheturn-offphaseduringnon-commutationperiodbutalsocompensatetorqueripplecausedbythecommutationcurrentduringcommutationperiod.
IndexTerms—BLDCmotor,commutation,PWM,torqueripple.
I.INTRODUCTION
TheBLDCmotorshavebeenwidelyusedduetoitsfeatures-asimplestructure,goodspeedadjustingperformance,highpowerdensity,lownoiseandsimplecontrol,etc.ItisahotspottosuppressthetorquerippleandimprovethecontrolperformanceofaBLDCmotorwiththetrapezoidalbackemf.
BLDCmotorsusuallyoperateinallkindsofPWMmodes,whichnotonlyaffectthedynamiclossofpowerswitchesandradiationuniformity,butalsoinfluencethetorqueripple.Itisaneffectivewaytosuppressthetorqueripplethroughchangingdcbuschoppercontroltoremainnon-commutationphasecurrentamplitudeconstant,butitresultsintoamorecomplextopology[1]-[3].Itisjustfitforlowspeedapplicationstocontrolnon-commutationphasecurrentamplitudetoregulatethecommutationtorqueripple[4].ItisanalyzedabouttheinfluenceresultedfromPWMONmodeonthetorqueripplein[5].Theideasin[1]-[3]aretoadoptdifferentsuppressionmethodsindifferentspeedinterval,buttheydon’ttaketheeffectbyPWMmodesonthesysteminaccount.Thepredictivecurrent,neuralnetworkcontrolandactivedisturbancerejectioncontroletcareintroducedtosuppressthetorqueripplein[9]-[12],butthecontrolalgorithmismorecomplicatedandharderforrealization.
DependingonthecommutationprocessofBLDCmotorsandtheeffectbyPWMmodesonthesystem,thepaperpresentsatorqueripplecom-pensationcontrolinPWM_ON_PWMmodeatdifferentspeedsbyseekingdifferentPWMmodulationratiosduringcommutationperiodasmotorrunsatlowspeedandhighspeed.Themethodretainstheoriginalto-pology,improvesthecontrolperformanceofthesystemdramatically,
andmoreoveriseasytorealize.
II.ELECTROMAGNETICTORQUEOFBLDCMOTOR
DURINGCOMMUTATIONPROCESS
AssumethattheBLDCmotoristhree-phasesymmetricalandY-connected,andneglecteddycurrentsandhysteresislosses,itsequivalentcircuitandmaincircuitareshowninFigure1.r,Laretheresistanceandinductanceofthestatorwindingsrespectively;
arethecounteremfsofthecorrespondingphasewindingsrespectively;
arethecorrespondingphasecurrentsrespectively.
(1)
Thecounteremfofeveryphasewindingisatrapezoidalwaveformwithaflat-topwidthgreaterthanorequalto1200electricaldegree,
anditsflat-topamplitudeisEm.Whenthemotorworksinthree-phasesix-state1200turn-onmode,thecurrentsdon’tcommutatesinstantaneouslyasaresultoftheinductanceofthearmaturewinding.Takethepowerswitch
and
’sturn-onto
and
’sturn-onforexample.Duringthecommutation,itisgainedasfollows
(2)
SupposethatthemechanicalangularvelocityoftherotorisΩ,thetoquecanbeobtainedasfollowsduringthecommutationprocess.
(3)
Itisobviousfrom(3)thatthetoqueisproportionaltothenon-commutationphasecurrentduringcommutation,i.e.thecommutationtorqueripplecanbeeliminatedsolongasnon-commutationphasecurrentremainsconstantduringcommutation.
III.COMMUTATIONPROCESSWITHOUTCONSIDERING
EFFECTBYPWMANDARMATUREWINDINGRESISTANT
AssumethatthecircuitstatuschangesfromphaseAandC’sturn-ontophaseBandC’sturn-on,phaseAcurrentflows
anddecaystozerogradually,whilephaseBcurrentincreasestothemaximumgraduallyandreachesitssteady-statevalue.ThecircuitequationduringcommutationwithoutconsideringtheeffectbyPWMcanbewrittenasfollows.
(4)
Comparedwiththewindingtimeconstant
ofaBLDCmotor,PWMperiodcanbethoughtsmallenough,andthen
.
Sotheeffectofthearmaturewindingresistantcanbeneglected.Moreovertheinitialandfinalvaluesofeveryphasecurrentequaleveryphasesteady-statecurrentvalue
beforeandafterthecommutation.Allphasecurrentsduringthecommutationcanbeobtainedfrom
(1),
(2)and(4).
(5)
Thenthetoqueduringthecommutationcanbewritten
(6)
From(5),theturn-offtimeofft∼ofphaseAandtheturn-ontimeont∼ofphaseBduringthecommutationprocessare
(7)
(8)
From(5)~(8),thecommutationbetweentwophasescan’tbecompletedinthesametimeas
i.e.themotorspeedislessthanacertainvalue,andasaresult
hasreacheditssteady-statevaluebefore
fallsto0,showninFig.2(I).What’smore,thecommutationleadstoanincreaseintheamplitudeoftorque.Thetorqueripplecanbeobtained
(9)
Thecommutationbetweentwophasescanbecompletedinthesametimeas
i.e.Themotorrunsatacertainspeed,andasaresult
hasexactlyreacheditssteady-statevaluejustas
fallsto0,showninFig.2(II).Inthiscase,thetorqueremainsconstantduringthecommutationanditsvalueequalsthetorqueduringthenon-commutationprocess
(10)
As
i.e.themotorspeedisgreaterthanacertainvalue,thecommutationbetweentwophasescan’tbecompletedinthesametime,andasaresult
doesn’treacheditssteady-statevaluewhen
fallsto0,showninFig.2(III).Thecommutationleadstoadecreaseintheamplitudeoftorque.Thetorqueripplecanbeobtained
(11)
IV.COMMUTATIONTORQUERIPPLECOMPENSATION
CONTROLINPWMMODE
Itisknownbasedonthepreviousanalysisthatthetorqueripplecausedbycommutationcanbefinallyeliminatedbytwoways-reducingcurrentrateofincreaseintheturn-onphasetosuppressthecurrentpulsationinthenon-commutationphaseasthemotorspeedislessthanacertainvalue;commutationoverlappingtokeeptheturn-onphaseconstantlyonandusePWMmodeinthepowerswitchesoftheturnoffphasestodecreasecurrentrateofdescendtosuppressthecurrentpulsationinthenon-commutationphaseasthemotorspeedisgreaterthanacertainvalue.
Assumethat
istheelectriclevelstatevariables
representsturn-onofpowerswitchordiodeintheupperarmofthecorrespondingphasewhie
representsturn-onofpowerswitchordiodeinthelowerarmofthecorrespondingphase.Asthemotorrunsatalowspeed,PWMisimplementedontheturn-onphase,i.e.turnoffphaseAwhilePWMonphaseB,inordertoreducecurrentrateofincreaseintheturn-onphaseduringcommutation.Thecircuitequationduringcommutationis
(12)
Itcanbeobtainedfrom
(1),
(2)and(12)
(13)
Sonon-commutationphasecurrentcanbegot
(14)
Where
iscontrolpulsedutycycleoftheturn-onphaseduringthecommutation.From(12)and(13),wecanget
(15)
So
(16)
Theturn-offtimeoftheturn-offphasetoffis
(17)
From(14),thefollowingequationmustbesatisfiedinordertokeeptheamplitudeofnon-commutationphasecurrentunvariedduringcommutation.
(18)
Because
duringcommutation,itmeansthattheinequationwillbesatisfiedonlyif
i.e.themotorrunsatalowspeed.Furthermoreasthemachineoperatesatalowspeed,itcanbeobtainedfrom(14)
(1)When,i.e.Undercompensatedcontrolduringcommutation,theamplitudeofnon-commutationphasecurrentdecreasesduringcommutation.
(2)When,i.e.Overcompensatedcontrolduringcommutation,theamplitudeofnoncommutationphasecurrentincreases
duringcommutation.
Substitute(18)into(17),wecangetthecommutationtimethatkeepstheamplitudeofnon-commutationphasecurrentconstantduringcommutationasthemachineoperatesatalowspeed.
(19)
Asthemotorrunsatahighspeed,overlappingcommutationisadoptedtoimplementPWMontheturn-offphaseandturnontheturn-offphaseconstantly,i.e.PWMonphaseAwhileturnonphaseBconstantly,
inordertoreducenon-commutationcurrentrippleduringcommutation.Thecircuitequationduringcommutationis
(20)
Itcanbeobtainedfrom
(1),
(2)and(20)
(21)
Sonon-commutationphasecurrentcanbegot
(22)
WhereDAAiscontrolpulsedutycycleoftheturn-offphaseduringthecommutation.
From(20)and(21),wecanget
(23)
Thereforeturn-onphasecurrentcanbeworkedout.
(24)
Theturn-ontimeoftheturn-onphasetonis
(25)
From(22),thefollowingequationmustbesatisfiedinordertokeeptheamplitudeofnon-commutationphasecurrentunvariedduringcommutation.
(26)
Because
duringcommutation,itmeansthattheinequationwillbesatisfiedonlyif
i.e.themotorrunsatahighspeed.Furthermoreasthemachineoperatesatahighspeed,itcanbeobtainedfrom(22)
(1)Wheni.e.Undercompensatedcontrolduringcommutation,theamplitudeofnon-commutationphasecurrentdecreasesduringcommutation.
(2)When,i.e.Overcompensatedcontrolduringcommutation,theamplitudeofnon-commutationphasecurrentincreasesduringcommutation.
Substitute(26)into(25),wecangetthecommutationtimethatkeepstheamplitudeofnoncommutationphasecur
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