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1、RESEARCHOFSVGBASEDONCASCADEH-BRIDGETOPOLOGYANDMODULATIONSTRATEGYABSTRACTStaticVarGeneratorSVGcancompensatereactivepowereffectively,maintainthesystemvoltagestability,improvepowerquality,improvesystempowerfacto匚Comparedwiththetraditionalreactivepowercompensationdevice,SVGhasobviousadvantages,represent
2、sthedevelopmentdirectionofdynamicreactivepowercompensationdevice.CascadedtopologyofSVGincreasesthecapacityandtheoutputvoltagelevel,whichmakestheapplicationofSVGpossibleinmiddleandhighvoltagesystems.Inordertoreduceswitchinglosses,thefiindamentalfrequencyoptimizationPAMmodulationstrategyisusedoncascad
3、eH-bridgetopologyinthepaper.EachH-bridgeareworkingonthefundamentalswitchingfrequency,reducingtheswitchinglosses.MeanwhiletheoutputvoltageofeachH-bridgeissuperimposedasstepwavetoapproximatethesinewave・Theinitialswitchinganglesaregettingbytheareaequivalenttheory,aftertheiterativecalculationtheoptimals
4、witchinganglesareobtained,makingtheharmonicdistortionleast.ThepulsecycletranspositionisusedontheDCside,makingthembalanceintheaveragemeaning.Thecurrentindirectcontrolmethodisusedbyadjustingpowerangle§tocontroltheoutputreactivepowersimplyandeffectively,inversesystemPIcontrolmethodisaddedtomakethedevic
5、eresponsespeedfaster.Simulationresultsshowtheeffectivenessofthemethodabove.BasedonthefundamentalfrequencyoptimizationPAMtoimprovethequalityoftheoutputwaveformfurther,thehybridmodulationmethodofPAM+PWMisintroducedinthispaper.ByaddingthePWMunit,theunipolar-frequencydoublingSPWMmodulationisappliedtoach
6、ievecurrentdirectcontrol,whichimprovesthecontrolaccuracyandresponsespeedofthedevice.ThePWMunitcancompensatetheoutputharmonicofthestepwaveeffectively,meanwhiletheharmonicself-compensatingmethodisintroduced,whichimprovesthequalityoftheoutputwaveformfurther,reducetheoutputharmonicdistortionfactor.Themo
7、delofcascadeSVGisbuiltinMatlab/Simulink,theresultprovesthevalidityofthismethod.KEYWORDS:SVGcascadeH-bridgetopology,fundamentalfrequencyoptimizationPAM,hybridmodulation,currentcontrolmethod目录摘要ABSTRACT
