电力电子技术第5版 教学课件 作者 王兆安 chapter04.ppt

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1、PowerElectronicsChapter4DCtoACConverters(Inverters)ApplicationsofInvertersConversionofelectricpowerfromDCtypeenergysourcestoACtypeloadBatteryPhotovoltaiccell(Solarcell)FuelcellAsapartofcompositeconverterAC-DC-ACfrequencyconverter(forACmotordrive)AC-DC

2、-ACconstant-voltageconstant-frequencyconverter(foruninterruptablepowersupplies)AC-DC-ACConvertersforinductionheatingAC-DC-AC-DCswitchingpowersuppliesOutline4.1Commutation4.2Voltagesourceinverters4.3Currentsourceinverters4.4Multiple-inverterconnectionsa

3、ndmulti-levelinverters4.1CommutationtypesAclassificationofinvertersSquare-waveinverters(arediscussedinthischapter)PWMinverters(willbediscussedinChapter6)TheconceptofcommutationBasicoperationprincipleofinvertersLoadS1S2S3S4iouoUd4typesofcommutationDevic

4、ecommutation:Fully-controlleddevices:GTO,IGBT,MOSFETLinecommutationPhase-controlledrectifierPhase-controlledACcontrollerThyristorcycloconverterLoadcommutationForcedcommutationLoadcommutationCondition:LoadcurrentisleadingloadvoltageApplication:capacitiv

5、eload,synchronousmotorForcedcommutation(capacitancecommutation)Direct-CoupledWithCoupling-InductorAnotherclassificationofcommutationsSelf-commutationDevicecommutationForcedcommutationLinecommutationLoadcommutation4typesofCommutationsExternalcommutatio

6、nForfully-controlleddevicesForthyristors2classesofinvertersVoltageSourceInverter(VSI)CurrentSourceInverter(CSI)4.2Voltagesourceinverter(VSI)DCsideisconstantvoltage,lowimpedance(voltagesource,orbulkcap)ACsidevoltageissquarewaveorquasi-squarewave.ACside

7、currentisdeterminedbytheload.Anti-paralleldiodesarenecessarytoprovideenergyfeedbackpath.(freewheelingdiodes,feedbackdiodes)+-CRLUdV1V2V3V4VD1VD2VD3VD4uoioFeaturesSingle-phasehalfbridgeVSIThecurrentconductingpathisdeterminedbythepolarityofloadvoltageand

8、loadcurrent.(Thisistrueforanalysisofmanypowerelectronicscircuits.)-RLUdiouoV1V2VD1VD2Ud2Ud2Themagnitudeofoutputsquare-wavevoltageisUd/2.uoUmiot1t2t3t4t5t6V1V2V1V2VD1VD2VD1VD2UG1UG2Single-phasefullbridgeVSIOperationprinciple+-CRLUdV1V2V3