3Phase Power Factor Correction Using Vienna Rectifier Approach and Modular Construction for ImprovWord文件下载.docx

3Phase Power Factor Correction Using Vienna Rectifier Approach and Modular Construction for ImprovWord文件下载.docx

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1.0Abstract:

Whileapplicationsfor1-PhasePFCarenowfamiliarandprevalent,thesameisnotthecasewith3-PhasePFC.Manyequipmentsusingkilowattsofpowerfrom3-Phasemainsshouldbecandidatesof3-Phasepowerfactorcorrection,becauseseveraladvantagesensue,bothtotheuseroftheequipmentandtotheutility.TheViennaRectifierapproachtoachieve3-Phasepowerfactorcorrectionoffersmanyadvantagesandconvenient,user-friendlyfeaturesascomparedtothetwo-level,six-switchboostPWMRectifier.Amongstthemare:

continuoussinusoidalinputcurrentswithunitypowerfactorandextremelylowdistortion;

noneedforaneutralwire;

reductioninvoltagestressandswitchinglossesofpowersemiconductorsbyalmost40%;

immunitytowardsvariationorunbalanceinmains3-Phasevoltagesorabsenceofoneofthephases;

widemainsvoltagerange:

320VACto575VAC;

verylowconductedcommon-modeEMI/RFI;

veryhighefficiencyoftheorderof97.5%,say,forpowerlevelsof10KWandinputlinevoltageof400VACandshortcircuitimmunitytofailureofcontrolcircuit.ThepaperdescribestheViennaRectifier’spowerstageandcontroltechniques,withparticularemphasisonmodularconstruction.WhatisproposedinthispaperisanewapproachofemployingFuzzyLogicforbuildingcontrollerforViennaRectifierDCBModulesfor3-PhaseACtoDCpowerconversion.

2.0Overview

Inthepastdecade,thereisgrowingawarenessaboutlinepollutionanddeterioratingpowerfactorduetoallpervadinginductiveandnon-linearloads.Utilitiesareasmuchconcernedastheusers.Passivepowerfactorcorrectiontechniquesareneitherconvenientnoreconomical;

theyneedbulkycomponentsandarenotadaptivetochangingneeds.Althoughmanysolutionswereofferedfor1-Phasepowerfactorcorrection,3-Phaseactivepowerfactorcorrectionwasseldomconsidered.Asallhighpowerequipmentsderiveelectricalpowerfrom3-Phasemains,incorporatinganactive3-PhasePFCfrontendcancontributesignificantlyinimprovingoverallpowerfactorandreducinglinepollution.

Inadditiontoloweringpowerbilltotheconsumers,improvedpowerfactoralsocontributestowardsconservationofenergyandhelpsinreducingairpollution,byvirtueoflessfossilfuelrequiredforgeneratingsameamountofelectricalpower.OtherresultanteffectsarelowerI2Rlosses,steadierterminalVoltages,releasedsystemcapacityandreducedcable&

switchgearsizes.ActivePFCfrontendsalsohelpmeettheIEEE519-92,IEC-555andEuropeanEN61000-3-2standardsforallowableharmoniccontentsofmains.

2.1Advantages

Althoughtherearesomepassiveandactive3-PhasePFCsolutions,ViennaRectifierisuniquebyvirtueofitsembodimentofseveraladvantages:

1.Itisa3-Phase,threelevelPWMrectifier,utilizingthreeMOSFETS,withcontrolledoutputVoltage;

threewireinput,notrequiringanyconnectiontoNeutral.

2.ItisadualboosttypePFCwithcontinuoussinusoidalinputcurrentandunidirectionalpowerflow

3.Itneedsonlythreeactiveswitches,i.e.MOSFETS

4.ItisOperationaleveninpresenceofunbalancedmainsoronlytwophases.

5.Totalswitchinglossesarereducedbyafactorofsix,assumingswitchingfrequencybelow50KHz.

6.AnymalfunctionincontrolcircuitdoesnotmanifestitselfinshortcircuitofoutputorPFCfrontend.

7.SinusoidalinputcurrentswithPowerFactor=0.997,THD<

5%andoverallefficiency>

97%areobtainablewithcurrentdesigns.

Ascanbeseen,ViennaRectifieristhe3-PhasePFCsolutionthatneedstobefullyexploited.ReadymadeViennaPowerSemiconductormodules,embodyingMOSFETS+FREDStomakeastandaloneDirectCopperBondedPowerCircuit,makeitquiteconvenientanduser-friendly.Powerful,yetinexpensive,microcomputersandDSPsmakeitattractivetodesigncompactcontrollersfortheViennaRectifiers.

AnewapproachofemployingFuzzyLogicforbuildingembeddedcontrollerforViennarectifierfor3-PhaseACtoDCpowerconversionisproposedhere.

3.0Applications

Alargenumberofindustrial,telecomandcomputingequipmentsnowuse3-Phasemainspower.Salientamongstthemare:

1.A.C.andD.CDrives

2.TelecommunicationPowerSupplies

3.UninterruptiblePowerSupplies

4.AirConditioningUnits

5.LargeComputerInstallations

6.Powersuppliesforallindustrialusessuchaswelding,surfacetreating,motioncontrol,largeappliancesandprocesscontrol

7.R.F.TransmittersandRadarTransmittersandrepeaterstations

8.Regulatedandtracking+350Vand–350VDC,forhighpowerbidirectionalservoamplifiersfordrivingheavy-dutycriticalloadssuchasAntennaTrackingandPositioningsystems.

AlltheaboveandmanymoresuchsystemsaregoodcandidatesforusingViennaRectifiersforachievingperformanceimprovementsaspertheadvantageslistedin2.1.

4.0ViennaRectifier

4.1ModusOperandi

ViennaRectifierasshowninFigure1,wasoriginallydevelopedattheTechnicalUniversityVienna.Itcomprisesasemiconductorswitch,say,aMOSFETineachphaselegofa3-Phasediodebridge.ByadjustingthewidthofthepulsethatturnsONtheMOSFET,correspondinglinecurrentisforcedtobesinusoidalandinphasewiththeVoltage.WhentheMOSFETisturnedONthecorrespondingphaseisconnected,viathelineinductor,tothecenterpointbetweenthetwooutputcapacitors.Thephasecurrentrises,throughtheMOSFET,duringthatpulseperiod,chargingthecapacitor.WhentheMOSFETisturnedoff,currenttapersthroughthediodehalfbridge（upperorlowerdependingondirectionofthecurrentflow）.

4.2ObjectiveofViennaRectifier

Itisahighlyefficientmethodofhighcurrent,3-PhaseACtoDCconversionandisparticularlyattractiveforachievingunitypowerfactoroperation.Infigure-1ACR,ACYandACBare440V,50Hz,3-PhasesinusoidallineVoltages.-Vdcand+VdcaretheDCoutputsconnectedtoload.Therearethreesemiconductorswitches,correspondingtoeachphaseT1,T2andT3.Theseareswitchedcontinuouslyataround25KHz.Theduty

Figure13-PhaseViennaRectifierConfiguration

CycleofthepwmswitchingissoprogrammedthatthecurrentdrawnfromeachphaseissinusoidalandinphasewiththecorrespondinglineVoltage,thusensuringnearunitypowerfactorandminimumtotalharmonicdistortion.

4.3Description

InViennaRectifierconfiguration,asshowninfigure-1,theoutputcapacitorissplitintwopartsastwoequalvaluecapacitors,C1andC2,connectedinseries.Acrosstheoutputcapacitorsthe–Vdcand+Vdcaredevelopedas3-Phasepeakdetectedoutputs.Aswitchforeachphaseisconnected,suchthatwhen“ON”,itconnectsthelinephasetothecenternodeofC1andC2throughaseriesinductance.Forashortswitchingperiod,（assuming10microseconds）,thecapacitorschargelinearly.Thisoffsets-Vdcand+Vdc.Theoffsetdependsonthecorrespondingphasevoltageandtheswitch“ON”timeduration.ThecommonnodeofC1andC2willhaveVoltagewithtriangularwaveshape,havingthreetimesthemainsfrequencyanditsamplitudewillbeonequarterofthephasevoltage.

Figure23-Phaselinevoltagesred,yellowandbluewith12timesegments

From0through11

4.4ViennaRectifierModules

LookingatFigure1,itbecomesapparentthatifoneweretoassembletheentire3-PhaseViennaRectifierPFCcircuitusingdiscretecomponents,manydifferentpowersemiconductorshavetobeconnectedtogether.Thisisnotonlyinconvenientandcostly,butalsoinvolvesadegreeofvariationinperformancefromunittounit.Theleadinductancesandparasiticcapacitancemaytendtooscillate,makingitsoperationathighenoughswitchingfrequencyataskbyitself.

Fortunately,readymadeViennaRectifierpowermodulesareavailableinDCB（DirectCopperBonding）ceramicbaseplate.Thesehaveanumberofusefulattributes:

1.Thesemoduleshaveisolationvoltageof3600VoltsAC,ensuringpersonalandequipmentsafetyandareU/Lrecognized.Thereisnoneedforexternalisolation.

2.Extremelylowpackageinductance,facilitatinghighspeedswitching

3.Easytomountonaprintedcircuitboardforeitherwavesolderingormanualsoldering

4.KelvinsourceforreliabledriverconnectionsfortheMOSFETS

5.TheMOSFET,builtusingHDMOSprocesshaslowRDS（on）andRGintandlowRthJSandlowinputandoutputcapacitancesandlowgatechargeandrisefalltimesforlowconductionandswitchinglosses

6.FREDS（FastRecoveryEpitaxialDiodes）havelowVFandextremelylowtrr

7.Consistentandpredictableperformancefromunittounit

4.5AdvantagesofDCB

TheDirectCopperBondedsubstrateshaveanumberofveryattractivefeaturesasgivenbelow:

1.Theyhaveverygoodmechanicalstrength,holdstableshapewithgoodadhesionandarecorrosionresistant

2.Theyhaveverygoodthermalconductivity,enhancingheatdissipationtoheatsink.Thisallowsveryclosepackagingofchips,furtherreducingleadinductancesandtranslatingmorepowerperunitvolume.

3.Verygoodthermalcyclingcapability,givingreliableperformanceovermanyyears

4.Thethermalexpansioncoefficientisclosetothatofsiliconsonointerfacelayersarerequired

5.Theyfeaturegoodheatspreadingthusleavingnohotspotsduringactualoperati