低压微网并联逆变器控制策略-研究

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1、AbstractRESEARCHONTHECONTROLSTRATEGYFORPARALLELINVERTERSINLOWVOLTAGEMICROGRIDABSTRACTWiththedevelopmentofsocietyandeconomy,people’sdemandforelectricityisincreasingdaybyday.Themicrogridcomposedbydistributedpowersourceshasattractedmoreandmoreattentionbecauseofitslowpollution,hig

2、hefficiencyandgoodcontrolabilityandsoon.Microgridhasallkindsofparallelmicro-sources,invertersaretheinterfacebetweenallkindsofmicro-sourcesandthegrid.Effectivecontrolstrategyforparallelinverterscanbeusedtoensurestableoperationofthesystemandprovidetheuserhighqualityelectricity.T

3、hus,studyonthecontrolstrategyforparallelinvertersinmicrogridhasvitalsignificance.Inthisthesis,theparallelinvertersinlowvoltagemicrogridweretakenastheresearchobject.Themathematicalmodelofinvertersbasedonthethreecoordinatesystemwasestablished.Andthenanalyzedtheselectoffiltersand

4、themethodforparameterssettingoffilters.Bycomparingthecontrolstrategiesforinterfaceinvertersinmicrogrid,inviewofthecontrolrequirementsofparallelinvertersinlowvoltagemicrogrid,droopcontrolwithnotie-linewaschosentodoresearch.Inviewofthegeneraldroopcontrolishighlydependentonthelin

5、eresistance,whichisdifficulttobeusedinlowvoltagemicrogrid.Improveddroopcontrolbasedonthelineresistancewasadopted,whichrealizedpowersharing.Butthebigcirculatingcurrentresultsfromthesmallnumericalofequivalentoutputimpedanceofinverters.Thevirtualimpedanceisaddedtoimproveoutputimp

6、edancecharacteristicofinverters,reducecirculatingcurrent,whilethevoltage-dropofinverters’outputincreaseatthesametime.Acontrolstrategybasedondynamicvirtualimpedanceforparallelinverterswasproposedtosolvetheaboveproblems.Thevalueofvirtualimpedanceadjustedunderthedynamicvirtualimp

7、edanceloop.Thiscontrolstrategycanreducevoltage-dropwhenthesystemsatisfiesstabilityconditions.Takingtwoparallelgrid-connectedinvertersasanexample,thesystemsimulationmodelwasbuiltunderMatlab/Simulinkenvironmentandtheproposedcontrolstrategywassimulated.Thesimulationresultsshowtha

8、ttheproposedcontrolstrategyinthispapercanrealizegoodpowershar