pwm整流器外文翻译Word格式文档下载.docx
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Fig.1showsthepowercircuitofthethree-phasePWMrectifier.Thevoltageequationsaregivenby
(1)
Fig.1.Three-phasePWMrectifierwithoutac-sidesensors.
where,andarethesourcevoltage,thelinecurrent,andtherectifierinputvoltage,respectivelyandaretheinputresistanceandtheinputinductance,respectively.Whenthepeaklinevoltage,angularfrequency,andinitialphaseanglearegiven,assumingabalancedthree-phasesystem,thesourcephasevoltageisexpressedas
(2)
Where
(3)
Atransformationmatrixbasedontheestimatedphaseangle,whichtransformsthree-phasevariablesintoasynchronousd–qreferenceframe,is
(4)
Transforming
(1)intothe–referenceframeusing(4)
(5)
wherepisadifferentialoperatorand.
Expressing(5)inavectornotation
(6)
where,
(7)
Takingatransformationof
(2)byusing(4)
(8)
(9)
Expressing(6)and(8)inadiscretedomain,byapproximatingthederivativetermin(6)byaforwarddifference[9],respectively,
(10)
(11)
WhereTisthesamplingperiod.
Fig.2.Overallcontrolblockdiagram.
BSystemControl
ThePIcontrollersareusedtoregulatethedcoutputvoltageandtheacinputcurrent.Fordecouplingcurrentcontrol,thecross-couplingtermsarecompensatedinafeedforward-typeandthesourcevoltageisalsocompensatedasadisturbance.Fortransientresponseswithoutovershoot,theanti-winduptechniqueisemployed[10].TheoverallcontrolblockdiagrameliminatingthesourcevoltageandlinecurrentsensorsisshowninFig.2.Theestimationalgorithmofsourcevoltagesandlinecurrentsisdescribedinthefollowingsections.
2PREDICTIVECURRENTESTIMATION
Thecurrentsof
and
cannotbecalculatedinstantlysincethecalculationtimeoftheDSPisrequired.Toeliminatethedelayeffect,astateobservercanbeused.Inaddition,thestateobserverprovidesthefilteringeffectsfortheestimatedvariable.
Expressing(5)inastate-spaceform,
(12)
(13)
where,
Andyistheoutput.
Transforming(12)and(13)intoadiscretedomain,respectively,
(14)
(15)
Then,theobserverequationaddinganerrorcorrectiontermtoisgivenby
(16)
WhereKistheobservergainmatrixand“^”meanstheestimatedquantity,and
isthestatevariableestimatedaheadonesamplingperiod.Subtracting(15)from(16),theerrordynamicequationoftheobserverisexpressedas
(17)
where
.Here,itisassumedthatthemodelparametersmatchwellwiththerealones.Fig.3showstheblockdiagramoftheclosed-loopstateobserver.
Thestatevariableerrordependsonlyontheinitialerrorandisindependentoftheinput.For(17)toconvergetothezerostate,therootsofthecharacteristicequationof(17)shouldbelocatedwithintheunitcircle.
Fig.3.Closed-loopstateobserver.
Fig.4.Shortpulseregion.
3EXPERIMENTSANDDISCUSSIONS
A.SystemHardwareConfiguration
Fig.5showsthesystemhardwareconfiguration.Thesourcevoltageisathree-phase,110[V].Theinputresistanceandinductanceare0.06Ωand3.3mH,respectively.Thedclinkcapacitanceis2350μFandtheswitchingfrequencyofthePWMrectifieris3.5kHz.
Fig.5.Systemhardwareconfiguration.
Fig.6.Dclinkcurrentsandcorrespondingphasecurrents(insectorV).
TheTMS320C31DSPchipoperatingat33.3MHzisusedasamainprocessorandtwo12-bA/Dconvertersareused.Oneofthemisdedicatedfordetectingthedclinkcurrentandtheotherisusedformeasuringthedcoutputvoltageandthesourcevoltagesandcurrents,whereacsidequantitiesarejustmeasuredforperformancecomparison.
OneoftwointernaltimersintheDSPisemployedtodecidethePWMcontrolperiodandtheotherisusedtodeterminethedclinkcurrentinterrupt.Consideringtherectifierblankingtimeof3.5s,A/Dconversiontimeof2.6s,andtheothersignaldelaytime,theminimumpulsewidthissetto10s.
A.ExperimentalResults
Fig.6showsmeasureddclinkcurrentsandphasecurrents.IncaseofsectorVofthespacevectordiagram,thedclinkcurrentcorrespondstofortheswitchingstateofandforthatof.Fig.7(a)showstherawdclinkcurrentbeforefiltering.Ithasalotofringingcomponentsduetotheresonanceoftheleakageinductanceandthesnubbercapacitor.Whenthedccurrentissampledattheendpointoftheactivevoltagevectorsasshowninthefigure,themeasuringerrorcanbereduced.
Fig.7.Samplingofdclinkcurrents.
Fig.8.Estimatedsourcevoltageandcurrentatstarting.
Toreducethiserrorfurther,thelowpassfiltershouldbeemployed,ofwhichresultiss
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