分布式电源

TheInfluenceofDistributedPoweraccesstotheGridContentsTheconceptandcharacteristicsofdistributedpowerTheadvantagesofthedistributedpoweraccesstothegridTheshortcomingsofthedistributedpoweraccesstothegrid1.1TheconceptofdistributedpowerDistributedpowerisdistributedattheuserendoftheenergyutilizationsystemandattheuser'ssiteorneartheelectricfieldbytheuserorindependentpowerproducersinvestmentconfigurationofthesmallcapacitypowerunitstomeettheneedsofaparticularuser.Itcanbeindependentofthepublicnetworkdirectlyonthepowersupplyoftheuser,alsocanbeconnectedtothenetworktouserpowersupply.1.2ThecharacteristicsofthedistributedpowerDistributedpowergenerationsystemasshowninGraph1.Graph1Distributedpowergenerationsystem1)Smallhydropower.Smallhydropowerunitcapacityissmall,theoperationandmaintenanceissimple,controlperformanceispoor.Themajorityofsmallhydropowerisnoadjustmentcapacityofrun-of-riverpowerstationsbyrunoffsituationconstraints,significantseasonalpowergenerationcapacity,theinterannualcanprovideelectricitynorbalanced,resultinginsystemloadforecastdeviationaffectsystemsecurityandstabilityoperation.2)Windpower.Windpowergenerationistousewinddrivenwheelrotation,thewindenergyisconvertedtomechanicalenergy,andthenthroughthegearboxdrivesgenerator.Windpowergenerationiscleanpollution-freeenergy,thegeneratingcostisrelativelylowandwindfarmoperationiseasy.Butwindpoweralsohassomelimitations,mainly:windenergydensity;lessefficientwindturbines;thenanadverseimpactonthegridintothegrid.DistributedwindpowergenerationsystemisshowninFigure2.Figure2Distributedwindpowergenerationsystem3)Photovoltaicpowergeneration.Solarphotovoltaicpowergenerationsystemcandirectsolarenergyintoelectricity,itmainlyconsistsofsolarpanels,controllerandinverter.4)Biomasspowergeneration.Biomasspowergenerationisthebiomasspowerplantasadirectcombustiontypesmallthermalpowerplantswithstraw,chaff,andotherbulkmaterialsasfuel,boilerturbinegeneratortogeneratepower,biomassdirectcombustionpowergenerationtechnologyhastheproblemoflowefficiency.2.TheadvantagesofthedistributedpoweraccesstothegridFigure3Distributedpoweraccesstothegrid1)Tosolvethedifficultproblemofruralelectricity.Strengthenthedevelopmentofruralhydropower,isnotonlyanimportantpartoftheelectricitysupply,butalsoansignificantwaytoutilizehydropowerresourcesandamelioratefarmers'productionandlivingconditions.2)Enhancingthereliabilityofelectricitysupply.Forthehighreliabilityrequirementsofusers,distributedgenerationcanbeusedasareserveunit,reducepowerloss,andinthepowergridaccidentcasetomaintaintheimportantuserpowersupply.3)Easytomeettheloaddemand,contributetotheefficientandlarge-scaleuseofrenewableenergy.3.1OntheinfluenceofpowergenerationplanningandschedulingDistributedpowercanbeusedasthenegativeloadforpowergrid,thereforetheeffectonpowergenerationplanningandschedulingissmall.GeneratedoutputofUncontrollabledistributedpowerisnotstable,thiswillincreasethevolatilityoftheaccessnetworkload.So,uncontrollabledistributedpowerexiststheproblemofpredictionaccuracy,tosomeextent,increasesthedifficultyoftheoperation.3.2OntheinfluenceofnetworklossFigure4isasimpleradialnetwork,thesystemlosscalculationformulais:)(2220DDQPVrLLossInthisformula,areloadactiveandreactivepower;risthelineofunitlengthresistance;Listhelinelength;VisLoadnodevoltage.Figure4asimpleradiationnetworkwithoutdistributedpowerFigure5asimpleradiationnetworkwithdistributedpowerAtadistancefromthesystembusforadistanceGpositionaccessactiveandreactivepoweroutputofdistributedpower,asshowninfigure5.Theintroductionofdistributedpowersupply,systemlossintothesystembustothedistributedbetweenthepowersourcelinelossanddistributedpowersupplytotheloadbetweenthelineintwoparts,accessdistributedpowersystemthelossis:)]22([22222GDGDGGDDossQQPPQPLGQPVrLLDPGGQP、Thedistributedpoweraccess,causesystemlossvariationis:)22(2220GDGDGGossossQQPPQPVrGLLLRDP)()22(22220DDGDGDGGossQPLQQPPQPGLLRasaindexthatmeasuresnetworklossrate,itsvalueis:Throughtheaboveanalysis,distributedpoweraccess,affectstheoriginalnetworkflowdistribution,necessarilyleadstothesystemlosschange.Relativetothesystemloadgeneralmodeofoperation,thelossofthesystemismainlyaffectedbythedistributedpowerposition,operationmodeanddistributedpowercapacityandloadoftherelativesizeoftheeffectsofthreefactors.Therefore,inthedistributedpowerlayout,throughthereasonableselectionofdistributedpowernetworklocationandcapacity,canminimizenetworklossandimprovethesystemofeconomicindex.3.3Ontheinfluenceofthepowerquality1)Voltagedeviation.Thedistributedpoweraccesstodistributionnetworkmakesvoltageregulationdifficult.Becausetheloadcurrentchanges,sothatthelinevoltagechanges,adjustmentandmaintenanceishard,voltagemayexceedthestandard;thefrequentstartupofdistributedgenerationmakesvoltageofdistributionnetworkoftenfluctuate.2)Voltageflicker.Themainreasonofvoltageflickeristheinstantaneouschangeoftheload.Whenthedistributedpoweraccesses,distributedpowerstart,theoutputpoweroftheshort-termupheavalanddistributedunitandsystemvoltagefeedbackcontrolequipmentinteractionarelikelytoc