低压微网并联逆变器控制策略研究

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1、AbstractRESEARCHONTHECONTROLSTRATEGYFORPARALLELINVERTERSINLOWVOLTAGEMICROGRIDABSTRACTWiththedevelopmentofsocietyandeconomy,people’sdemandforelectricityisincreasingdaybyday.Themicrogridcomposedbydistributedpowersourceshasattractedmoreandmoreattentionbecauseofitslowpollution,h

2、ighefficiencyandgoodcontrolabilityandsoon.Microgridhasallkindsofparallelmicro-sources,invertersaretheinterfacebetweenallkindsofmicro-sourcesandthegrid.Effectivecontrolstrategyforparallelinverterscanbeusedtoensurestableoperationofthesystemandprovidetheuserhighqualityelectrici

3、ty.Thus,studyonthecontrolstrategyforparallelinvertersinmicrogridhasvitalsignificance.Inthisthesis,theparallelinvertersinlowvoltagemicrogridweretakenastheresearchobject.Themathematicalmodelofinvertersbasedonthethreecoordinatesystemwasestablished.Andthenanalyzedtheselectoffilt

4、ersandthemethodforparameterssettingoffilters.Bycomparingthecontrolstrategiesforinterfaceinvertersinmicrogrid,inviewofthecontrolrequirementsofparallelinvertersinlowvoltagemicrogrid,droopcontrolwithnotie-linewaschosentodoresearch.Inviewofthegeneraldroopcontrolishighlydependent

5、onthelineresistance,whichisdifficulttobeusedinlowvoltagemicrogrid.Improveddroopcontrolbasedonthelineresistancewasadopted,whichrealizedpowersharing.Butthebigcirculatingcurrentresultsfromthesmallnumericalofequivalentoutputimpedanceofinverters.Thevirtualimpedanceisaddedtoimprov

6、eoutputimpedancecharacteristicofinverters,reducecirculatingcurrent,whilethevoltage-dropofinverters’outputincreaseatthesametime.Acontrolstrategybasedondynamicvirtualimpedanceforparallelinverterswasproposedtosolvetheaboveproblems.Thevalueofvirtualimpedanceadjustedunderthedynam

7、icvirtualimpedanceloop.Thiscontrolstrategycanreducevoltage-dropwhenthesystemsatisfiesstabilityconditions.Takingtwoparallelgrid-connectedinvertersasanexample,thesystemsimulationmodelwasbuiltunderMatlab/Simulinkenvironmentandtheproposedcontrolstrategywassimulated.Thesimulation

8、resultsshowthattheproposedcontrolstrategyinthispapercanrealizegoodpowershar