电力电子装置及系统 课件 Topic 8-Pulse-width-modulation current source inverter

Topic8:PWMCurrentSourceInverter1PWMCSIfedMVdriveSource:RockwellAutomationTopic8:PWMCurrentSourceInverterSingleBridgeInverterTrapezoidalModulation(TPWM)SelectiveHarmonicElimination(SHE)SpaceVectorModulation(SVM)DualBridgeInverter2SingleBridgeInverter3InverterTopologyFeatures:-Simpletopology–noantiparalleldiodes-Reliableshortcircuitprotection–constantdccurrent-Verylowdv/dtonmotorterminalsSymmetricalGCTsFunctionofCf

:-AssistGCTcommutation-ReduceharmonicdistortionSingleBridgeInverter4DCCurrentSourceIdImplementationofdccurrentsource:-usealargesizedcchoke–makingIdsmooth;-usedccurrentfeedbackcontrol–keepingIdconstantSingleBridgeInverter5ModulationTechniques•TrapezoidalPWM(TPWM)•SelectiveHarmonicElimination(SHE)•SpaceVectorModulation(SVM)•ConstraintsonSwitchingPatternDesign-dccurrentId

cannotbeinterrupted-inverteroutputcurrentwaveformmustbedefined.•Atanytimeinstant,onlytwoswitchesareturnedon,oneconnectedtothepositivedcbus,andtheothertothenegativedcbus.TrapezoidalModulation6TrapezoidalPWM(TPWM)Numberofpulsesperhalfcycle:Np=7TrapezoidalModulation7HarmonicContent(TPWM)•Np=15•Fundamentaldoesnotchangemuchwithma•ma=0.85TrapezoidalModulation8Waveforms(TPWM)SelectiveHarmonicElimination(SHE)9Principle•Notalltheswitchinganglesareindependent.•OnlytwoharmonicscanbeeliminatedwithNp=5.•Numberofharmonicstobeeliminated:•Nomodulationindexcontrol–themagnitudeofinverteroutputcurrentiscontrolledbyIdSelectiveHarmonicElimination10FourierAnalysisSelectiveHarmonicElimination11FourierAnalysisExpressionforanSelectiveHarmonicElimination12SwitchingAngleCalculationToEliminatenthharmonic,setan=0For5th,7thand11thharmonicelimination:SelectiveHarmonicElimination13SwitchingAngle(SHE)SelectiveHarmonicElimination14InverterWaveforms(SHE)Harmoniceliminated:5th,7thand11th;fsw=420HzSelectiveHarmonicElimination15Waveforms(SHE)SpaceVectorModulation16SpaceVectorModulation•Sixactivecurrentvectorsandonezerovector•SixsectorsSpaceVectorModulation17SwitchingStateSpaceVectorModulation18SwitchingStates&SpaceVectors[1]:Upperswitchon[-1]:Lowerswitchon[0]:Noneoftheswitchesinalegturnedon[2]:Bothswitchesinalegturnedon(bypassmode)SpaceVectorModulation19DwellTimeCalculationFollowingthesameprincipleofSVMfortheNPCinverterSpaceVectorModulation20DwellTimeCalculationSpaceVectorModulation21SwitchingSequenceRequirements:1)Transitionfromoneswitchingstatetothenextinvolvesonlytwoswitches;2)Atanytimeonlytwoswitchesareon.SpaceVectorModulation22SwitchingSequence(Overonecycle)SpaceVectorModulation23InverterOutputWaveforms(SVM)f1=60Hz,fsw=540Hz,Np=9andma=1SpaceVectorModulation24HarmonicSpectrum(SVM)f1=60Hz,fsw=540Hz,Np=9andma=1SpaceVectorModulation25HarmonicSpectrum(SVM)Dual-BridgeInverter26ConverterConfigurationDual-BridgeInverter27SpaceVectorDiagram19vectorsand51switchingstatesDual-BridgeInverter28DCCurrentBalanceControlCurrentpathswithswitchingstate[16;56