电力电子技术第5版 教学课件 作者 王兆安 chapter08.ppt

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1、PowerElectronicsChapter8Soft-SwitchingTechniquesPursuingofhigherswitchingfrequencyBenefitsBetterwaveformPWMwaveformwillbeclosertoexpectedwaveformHarmonicsiseasiertobefilteredFasterresponseSmallervolumeandweight4.44fNf=4.44fNABDisadvantagesofhigherswitchingfreque

2、ncyDisadvantagesHigherpowerlossesonpowersemiconductordevicesPowerloss=fxEnergylossateachswitchingMoresevereelectromagneticinterference(EMI)SteeperedgesintroducemorenoisesEasiertoberadiatedSolutionSoft-switchingtechniquesOutline8.1Basicconceptsonsoft-switching8.2

3、Classificationofsoft-switchingtechniques8.3Typicalsoft-switchingcircuitsandtechniques8.1Basicconceptsonsoft-switchingHard-switchinga)Turning-onb)Turning-offTheprocessofpowersemiconductordevicehard-switchingTheconceptofsoft-switchingSoft-switchinga)Turning-onb)Tu

4、rning-offTheprocessofpowersemiconductordevicesoft-switchingTwotypesofsoft-switchingZVS—Zero-voltageswitchingSpecificallymeanszero-voltageturn-on,i.e.,thevoltageacrossthedeviceisreducedtozerobeforethecurrentincreasesZCS—Zero-currentswitchingSpecificallymeanszero-

5、currentturn-off,i.e.,thecurrentflowingthroughthedeviceisreducedtozerobeforethevoltageincreases8.2Classificationofsoft-switching　techniquesQuasi-resonantsoft-switchingZVSPWM(zero-voltage-switchingPWM)andZCSPWM(zero-current-switchingPWM)ZVTPWM(zero-voltage-transit

6、ionPWM)andZCTPWM(zero-current-transitionPWM)TheconceptofbasicswitchcellQuasi-ResonantConverter—QRCZVSQRCZCSQRCZVSMRC(multi-resonantconverter)ResonantDClinkconverterBasicswitchingcellsforQRCZVSPWMconverterandZCSPWMconverterFeature:useofauxiliaryswitchBasicswitchi

7、ngcellsfora)ZVSPWMandb)ZCSPWMZVTPWMconverterandZCTPWMconverterFeature:auxiliaryswitchisinparallelwithmainswitchBasicswitchingcellsfora)ZVTPWMandb)ZCTPWM8.3Typicalsoft-switchingcircuitsandtechniquesZVSQRCResonantDClinkconverterPhase-shiftfullbridgeZVSPWMconverte

8、rZVTPWMconverterZVSQRCto~t1t1~t2SuS(uCr)iSiLruVDt0t1t2t3t4t6t0tttttt5OOOOOResonantDClinkconverterCircuitEquivalentcircuittoRDCLSummaryofQRCDisadvantagesVoltagestressi