simulink_power_system02

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1、Thyristor-BasedHVDCLinkRECTIFIERscopetoobservetheDCFaultprotectionaction.Restartthesimulation.Inverter5-555TransientsandPowerElectronicsinPowerSystemsFigure5-13:DCLineFaultontheRectifierSideAtfaultapplication(t=0.7s),theDCcurrentincreasesto2.2p.u.andtheDCvoltagefallstozeroattherec

2、tifier.ThisDCvoltagedropisseenbytheVoltageDependentCurrentOrderLimiter(VDCOL)andtheDCFaultprotection.TheVDCOLreducesthereferencecurrentto0.3p.u.attherectifier.ADCcurrentstillcontinuestocirculateinthefault.Then,att=0.77s,therectifierαfiringangleisforcedto166degreesbytheDCFaultprote

3、ctionafterdetectingalowDCvoltage.Therectifiernowoperatesininvertermode.TheDClinevoltagebecomesnegativeandtheenergystoredinthelineisreturnedtotheACsystem,causingrapidextinctionofthefaultcurrentatitsnextzerocrossing.Thenαisreleasedatt=0.82sandthenormalDCvoltageandcurrentrecover5-56T

4、hyristor-BasedHVDCLinkinapproximately0.5s.Notice,thetemporarymodechangeintheRectifiercontrolsbetween1.18sand1.25s.ACLine-to-GroundFaultattheInverterNowmodifythefaulttimingstoapplyaline-to-groundfault.IntheDCFaultblock,changethemultiplicationfactorof1to100,sothattheDCfaultisnowelim

5、inated.IntheA-GFaultblock,changethemultiplicationfactorintheswitchingtimesto1,sothatasix-cycleline-to-groundfaultisnowappliedatt=0.7sattheinverter.Restartthesimulation.5-575TransientsandPowerElectronicsinPowerSystemsFigure5-14:Rectifier,InverterSignalsforanACLineFaultonInverterSid

6、e5-58Thyristor-BasedHVDCLinkFigure5-15:VoltagesandCurrentsonthe50HzSideforanACLineFaultontheInverterSideNoticethe120HzoscillationsintheDCvoltageandcurrentsduringthefault.AnunavoidablecommutationfailureoccursattheinverterattheverybeginningofthefaultandtheDCcurrentincreasesto2p.u.Wh

7、enthefaultisclearedatt=0.8s,theVDCOLoperatesandreducesthereferencecurrentto0.3p.u.Thesystemrecoversinapproximately0.35safterfaultclearing.5-595TransientsandPowerElectronicsinPowerSystemsLookatthewaveformsdisplayedonthePROTECTIONINVERTERscope.TheLowACVoltageblockdetectsthefaultandl

8、ockstheDCFaultprotectionthatinthi