外文翻译关于交流伺服驱动器的死区效应的分析与补偿.docx
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外文翻译关于交流伺服驱动器的死区效应的分析与补偿
外文资料原文
AnalysisAndCompensationOfDeadTimeEffects
ForTheACServoDriver
HaitaoQin1,AnwenShen2,QiaoZhang3,WenyuWang4
DepartmentofControlScienceandEngineering,HuaZhongUniversityofScienceandTechnology,China
Abstract—Aon-linedeadtimecompensationmethodforthealternatingcurrent(AC)servoisproposed.ByapplytheFastFourierTransform(FFT)tothecompensatingvoltageinoneperiodofthreephaseoutputcurrent,withoutanyadditionalhardware,thedeadtimeeffectsiseliminatedbycompensatethe1th,5th,7thharmoniccomponentsonly.Theresultsofsimulationsandexperimentswelldemonstratetheeffectivenessoftheproposedmethod.
IndexTerms--AC-Servo,Dead-TimeCompensation,Permanentmagnetsynchronousmotor(PMSM).
I.INTRODUCTION
Forthestorageeffectofpowerdevice,it’sverynecessarytosetadead-timeonbothswitchesinaninverterlegtoavoidtheshoot-throughinthedc-link.AccordingtotheInsulatedGateBipolarTransistor’s(IGBT)performance,weusuallysetthedeadtimeas2~5us,thisdistortsthevoltagesourceinverter’s(VSI)outputvoltage,resultinginphasecurrentdistortions,torqueripplesanddegradationsofcontrolperformance.Toovercomethedead-timeeffect,variousapproacheshavebeenstudiedandapplied.Conventionally,errorvoltageduetothedead-timeeffectcanbepre-calculatedandcompensatedbyaddingthemtothe3-phasereferencevoltageaccordingtothephasecurrentpolarity[1-2].Aon-linecompensationmethodispresentedin[3],computetheerrorvoltagebycomparethereferencevoltagewiththerealvoltage,andthenaddthistonextreferencevoltageasthenewreference.Inthisapproach,theerrorvoltagewhichcausedbymanyreasonssuchasdead-time,dc-linkvoltagedrops,etccanbeeliminated.However,estimationoftherealvoltageshouldusetheparameterofmotorwhicharenotfixedvaluebutvaryingwhileatworking.In[4],dead-timeeffectiscompensatedbymodifiedPWMgatesignalswithhardwarecircuits.In[6],amethodwhichchangethePWMgatesignalon-linebasedonthepolarityofphasecurrentispresented.Alltheapproachesmentionedabovecaneliminatethedeadtimeeffectgreatlyandhaveagoodperformance,however,withtheincreaseofcomplexityofthesoftwareandhardware,whichrestrictthepracticability.Thus,Inthepaper,amethodbasedonthe2-phasestationaryframeisproposed.Theproposedmethodproducesthecompensatingsignalbyusethephaseofthecurrentonly,doesnotneedanyadditionalhardwarecircuits.
II.ANALYSISOFDEAD-TIMEEFFECT
It’sconvenienttoanalyzethedead-timeeffectsfromonephaselegoftheinverterandextendtheresulttootherphaselegs.Figure.1showsthebasicconfigurationofone
phaselegoftheinverter.Definethedirectionofphasecurrentflowtoloadispositive.
Figure.1.onephaselegoftheinverter
A.whenphasecurrentiaispositive:
WhenupperswitchA+turnon,lowerswitchA-turnoff:
Duringthedead-timeandbeforetheA+turnoncompletely,thevoltageofpointaisclampedto–Udc/2fortheD-turnedon,thephasecurrentflowsthroughA+
untilA+turnedon,thus,theerrortimecausedbydeadtimeeffectisTd+ton,wheretonistheIGBT’sturnondelaytime.
WhenupperswitchA+turnoff,lowerswitchA-turnon:
phasecurrentflowsthroughA+beforeA+turnedoff,andflowsthroughD-whenturnedoff.Thus,theerrortimecausedbydead-timeeffectistoff,wheretoffistheIGBT’sturnoffdelaytime.
B.whenphasecurrentiaisnegtive:
Whenupperswitch(A+)-turnon,lowerswitch(A-)turnoff:
phasecurrentflowsthroughA-beforeA-turnedoff,andflowsthroughD+whenturnedoff.Thus,theerrortimecausedbydead-timeeffectistoff.Whenupperswitch(A+)turnoff,lowerswitch(A-)turnon:
Duringthedead-timeandbeforeA-turnoncompletely,thevoltageofpointaisclampedto+Udc/2forD+turnedon.Thus,theerrortimecausedbydeadtimeeffectisTd+ton.
Figure.2(a)showstheidealgatesignalpatterns,Figure.2(b)showsthepracticalsignalpatternsconsideringthedead-time,Figure.2(c)showstheactualoutputvoltageconsideringthedead-timeandswitchingtimeforia>0andia<0.
Figure.2.practicalswitchingpatternconsideringthedead-timeandturn
on/offtimeofswitchingdevices.(a)idealgatesignalpatterns.(b)
practicalsignalpatternsconsideringthedead-time.(c)actualoutput
voltageconsideringthedead-timeandswitchingtime
TheaverageerrorvoltagecanbecalculatedfromFigure.2asin
(1):
(1)
Where
.
Accordingto
(1),themostobviousimpactofdeadtimeeffectislowertheoutputvoltage,resultinginharmonicsinphasecurrent,torquerippleandspeedfluctuation,especiallyinlowspeed.
II.COMPENSATIONOFDEAD-TIMEEFFECT
Themainprincipleofthecompensationisproduceasameamplitudeandoppositesignvoltagewiththeerrorvoltagetodecreaseoreliminatetheeffectofdead-time.From
(1),amplitudeoftheerrorvoltagewhichdependondead-time,switchperiod,switchingtimeanddc-linkmvoltageisfixedforoff-linecompensation.Thekeyofcompensationistojudgepolarityofthephasecurrent.It’sdifficulttojudgethepolarityofphasecurrentaccuratelyintherealcontrolsystem,however,andtheambiguityatthezeropointofphasecurrentwilldeterioratethecompensationeffect.Thus,inthispaper,acompensationmethodwhichdependonthephaseofcurrentonlyinthe2-phasestationary(α/β)frameisproposed.Theerrorvoltagedependonthepolarityofphasecurrent,sothreephasecurrentwillhavesixdifferentcombinationsoftheerrorvoltagevector.Table.Ishows,theerrorvoltageandit’svectoratdifferentpolarityofthreephasecurrent,where
.
TABLEI
ERRORVOLTAGEVECTORACCORDINGTOTHEPOLARITYOFTHREE
PHASECURRENT
Figure.3showsthecompensationvoltagevector.The
compensationvoltagevectormovediscontinuously,and
itstrajectoryishexagon.
Figure.3.compensationvoltagevector
Thecurrentvectorin2-phaserotary(d/q)frameasshowninFigure.4.ThephaseofcurrentvectorcanbeobtainedfromFigure.4as:
Figure.4.Phaseofcurrentvector
TherotorfluxorientatedcontroltechnologybeusedtocontrolPMSMintheservosystem,andrealizedecouplingbycontrol
therefore,
.
CurrentvectorwithrespecttoerrorvoltagevectorasshowninTable.II.
TABLE.II
CURRENTVECTORWITHRESPECTTOERRORVOLTAGEVECTOR
Byconsideringtheperiodicityandparityofthecompensationvoltagevectorintheα/βframe,theFouriertransformcanbesummarizedasin
(2):
(2)
Wherenacanbecalculatedasin(3):
(3)
Inasimilarway,nbisrepresentedasin(4):
(4)
Using(3)and(4)through
(2),thecompensationvoltagein/framecanbeobtainedas:
(5)
From(5),therearenozero-phasevoltagesuchas3-th,9-thharmonics,andhigheroddharmonicshavelittleeffecttotheoutputvoltagedistortion.Therefore,itssufficienttodecreasethedead-timeeffectbycompensatefundamental,5-thand7-thharmonicsonly.Theblockdiagramofvectorcontrolcontainingdead-timecompensationasshowninFigure.5.
Figure.5.BlockdiagramofFOCcontainingthedead-time
Compensation
IV.SIMULATIONOFDEAD-TIMEEFFECT
Apreliminarysimulationanalysishasbeenperformedtotestthecompensationvalidation.ThesimulationmoduleoftheservosystemhasbeensetupinaccordancewithFigure.5.ParametersofthetestedmotorislistedinTable.III.Asoperationcondition,a60r/minreferencespeedanda2Nmloadtorquehavebeenimposed.A10KHzmodulationfrequencyforthecontrolhasbeenimposed,whilea4.8usdelaytimehasbeenconsideredasthesystem’sdead-time.
TABLE.III
PARAMETERSOFTHETESTEDMOTOR
Figure.6showsthesimulationresultsofcurrentandvoltagebeforeandafterdeadtimecompensatebeenused.Wecanseethatthephasecurrentisdistortedseverelyduetothedead-timeeffects,andthedistortionisremarkablyreducedintheproposedscheme.
(a)withoutdeadtimeeffect
(b)withdeadtimeeffect
Figure.6.Simulationresultsofvoltageandcurrent
V.EXPERIMENTRESULT
TheproposedcompensationmethodisrealizedusingaDSP-basedcontrolsystemofPMsynchronousmotor.Theprocessoristhefixed-pointDSP(TMS320LF2407A)withaclockof40MHz.TheHCPL-7840isolationamplifierisusedtomeasurethephasecurrentandthedclinkvoltage,andthemeasuredsignalsareconvertedtodigitalvaluebyusingaanalog-to-digitalconverters(ADCs)witharesolutionof10-bits.Aincrementalencoderwitharesolutionof2500-pulse/revandapositionprocessorareemployedtoobtainpositionoftherotorfluxandmeasuretherotorspeed.Theresolutionofspeedmeasurementis2r/minconsideringtheresolutionofencoderandthesystemsamplingperiod.Thethree
phaseinverterisconstructedbyusingaintelligentpowermoduleincludingsixIGBTs,gatedrives,andprotectioncircuits.Theperformanceofthecontrolsystemwiththeproposedcompensationschemeiscomparedwiththenocompensationscheme.Figure.7(a)showstheexperimentresultsofphasecurrentwithoutdead-timecompensation.Withoutacompensationscheme,thedead-timecausestheundesiredcurrentpopulationinthepahsecurrents.However,intheproposedcompensationscheme,thesedistortionisremovedperfectlyasshowninFigure.7(b).
(a)withoutcompensation
(b)withcompensation
Figure.7.Experimentresultsofa-phasecurrent
Figure.8describesthesteady-statespeedat60r/min.Consideringtheerrorsofmeasurementis2r/min,thespeederrorwithoutdeadtimecompensationis2r/min,andthisvaluereducedto0whentheproposedcompensationmethodisapplied.
(a)withoutcompensation
(b)withcompensation
Figure.8.Experimentresults