电力电子装置及系统 课件 Topic 7-Multilevel neutral point clamped inverter

Topic7:MultilevelNeutralPointClampedInverter1Three-LevelNPCInverterBasedMVDriveSource:ABB(ACS1000)Topic7:MultilevelNPCInvertersThree-levelNPCInverterSpaceVectorModulationNeutralPointVoltageControlHigh-levelNPCInverters2MultilevelInverterTopologies3Per-PhaseDiagramMultilevelNPCInverters4InverterConfigurationClampingdiodes:DZ1andDZ2(PhaseA)MultilevelNPCInverters5SwitchingStateComplementarySwitchpairs:S1andS3;S2andS4;MultilevelNPCInverters6GateSignalArrangementsInverterphasevoltagevAZhasthreelevels:E,0and–EMultilevelNPCInverters7InverterOutputWaveformsSpaceVectorModulation8SpaceVectors•Three-phasevoltages

(1)•Two-phasevoltages(2)•Spacevectorrepresentation(3)(2)(3)

(4)whereSpaceVectorModulation9SpaceVectors(Example)Switchingstate[POO]on-stateswitches:PhaseA:uppertwoswitches[P]PhaseB:middletwoswitches[O]PhaseC:middletwoswitches[O]Fromwhich

and

(5)•Substituting(5)to(4)givesaspacevector(6)Totalswitchingstates:27Totalspacevectors:19SpaceVectorModulation10SpaceVectorsDiagram19spacevectors:Zerovector:V0Smallvectors:V1–V6Mediumvectors:V7–V12Largevectors:V13–V18SpaceVectorModulation11SwitchingStatesandSpaceVectorsRedundancy:Zerovector–threeswitchingstatesSmallvectors–twostatespervectorSpaceVectorModulation12SwitchingStatesandSpaceVectorsNoredundantswitchingstatesformediumorlargevectorsSpaceVectorModulation13SectorDefinition•Vref:Referencevector,rotatinginspaceatacertainspeed;•Allothervectorsarestationary.SpaceVectorModulation14SVMPrinciple•Foragivenlengthandpositioninspace,Vrefcanbeapproximatedbythreenearbystationaryvectors;•Basedonthechosenstationaryvectors,switchingstatesareselectedandgatesignalsaregenerated;•WhenVrefpassesthroughsectorsonebyone,differentsetsofswitchesareturnedonoroff;•WhenVrefrotatesonerevolutioninspace,theinverteroutputvoltagevariesonecycleovertime;•TheinverteroutputfrequencycorrespondstotherotatingspeedofVref;•TheinverteroutputvoltagecanbeadjustedbythemagnitudeofVref.SpaceVectorModulation15SectorDefinition•Vref:Referencevector,rotatinginspaceatacertainspeed;•Allothervectorsarestationary.SpaceVectorModulation16DwellTimeCalculationDwelltimeistheduty-cycletimeofselectedswitchesduringthesamplingperiodTs.•Selectthreeneareststationaryvectors•Usevolt-secondbalancingprinciple(a)SectorIFourRegionsSpaceVectorModulation17DwellTimeCalculation•Fromequation(a)Ta,TbandTc–dwelltimesforV1,V7andV2–modulationindex

SpaceVectorModulation18SwitchingSequence(Seven-segment)•GeneralDesignRequirementsa)Thetransitionfromoneswitchingstatetothenextinvolvesonlytwoswitchesinthesameinverterleg,onebeingturnedonandtheotherturnedoff;andb)ThetransitionforVrefmovingfromonesector(oroneregion)tothenextrequiresnoorminimumnumberofswitchings.Note:Theswitchingsequencedesignisnotunique,buttheaboverequirementsshouldbesatisfiedforswitchingfrequencyminimization.SpaceVectorModulation19SwitchingSequence(Seven-segment)•AssumingVrefisinRegion4ofSectorI,threevectorsareselected:V2,V7andV14SpaceVectorModulation20SwitchingSequence(Seven-segment)Note:Switchingsequencerequirementa)issatisfied.SpaceVectorModulation21SwitchingSequence(Seven-segment)SpaceVectorModulation22SwitchingSequence(Seven-segment)Note:Switchingsequencerequirementb)issatisfied.•Deviceswitchingfrequency:•Samplingfrequency:•Fundamentalfrequency:SpaceVectorModulation23SimulatedWaveforms(Seven-segment)•Deviceswitchingf1=60Hz,Ts=1/1080sec,ma=0.8,fsw=570Hz•vABisnothalfwavesymmetrical;andcontainsbotheven-andodd-orderharmonics.SpaceVectorModulation24SimulatedWaveforms(Seven-segment)f1=60Hz,Ts=1/1080sec,ma=0.8,fsw=570HzSpaceVectorModulation25HarmonicContent(Seven-segment)SpaceVectorModulation26LaboratoryPrototypeatRyersonSpaceVectorModulation27MeasuredWaveformsSpaceVectorModulation28MeasuredWaveforms(witheven-orderharmonicelimination)NeutralPointVoltageControl29NeutralPointVoltageDeviationTheneutralpointvoltagevzcanbecontrolledbyP-andN-typesofsmallvectorsNeutralPointVoltageControl30NeutralPointVoltageControlNeutralPointVoltageControl31NeutralPointVoltageControlNote:Risusedonpurposetomakethedcvoltageunbalance.High-LevelNPCInverters32InverterTopologiesHigh-LevelNPCInverters33SwitchingStateHigh-LevelNPCInverters34ComponentCountNote:Thenumberofclampingdiodesincreasessubstantiallywiththevoltag