英文风电涡轮机分类分析及翻译.docx

英文风电涡轮机分类分析及翻译.docx

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英文风电涡轮机分类分析及翻译

ComparisonandEvaluationofThreeMainTypesofWindTurbines1

Abstract—Manydifferenttypesofwindturbineshavebeenconnectedtothepowersystemsoftheworldinrecentyears,andtheirprimaryfocuswastodesignthemtobemoreefficientandreliable.Inthispaper,threemaintypesofwindturbinesaremodeledandcompared.Theperformancesofthesewindturbinesduringaseverethree-phasefaultattheendofatransmissionlinearesimulatedandtheircharacteristicsareanalyzed.Finallytheoperationandmaintenancecostsofthesewindturbinesarediscussedandproperapplicationsofthesewindturbinesarepointedout.

IndexTerms—windturbine,modeling,fixedspeedwindturbine,doublyfedinductiongenerator,multipolepermanentmagnetsynchronousgenerator。

I.INTRODUCTION

Asthedemandforenergyissteadilyincreasing,expertshavebeenlookingfornewformsofresourcestoreducedependenceonfossilenergy.Comparedwithsolarandotherrenewableenergy,windenergyischeaperandmorereliable.Overtheyearswindpowerbecamethemostrapidlygrowingrenewableenergyinelectricitygeneration.TheinstalledcapacityandnetgenerationofwindpowerinUSfrom1992to2005areshowninFig.1.

ThetotalamountofelectricitythatcouldpotentiallybegeneratedfromwindintheUnitedStateshasbeenestimatedat10.8trillionkWhannually,butinstalledwindenergygeneratingcapacitynowtotalsonly9,149MW,andisexpectedtogenerateabout24.8billionkWhofelectricityin2006—thatisstilllessthan1%ofU.S.electricitygeneration（4.0trillionkWhin2004）.AccordingtoFig.1,theaveragecapacityfactorofwindturbinesis21.7%,whichisacceptableforavariableenergysourcewithnofuelcost.

Asapracticalgreensource,windpowercanprovideelectricpowerwithminimalenvironmentalpollution.Comparedtocoalandnaturalgas,thewindsourceisrenewablewithoutanyworryaboutthefuturedepletionofwindreserve.Butwindenergycanprovideonlyapartoftheelectricaldemandandconsumercannotrelycompletelyonwindpoweredelectricenergybecausewindisnotavailableallthetime.Expertshavelookedintothepossibilityofstoringelectricalenergy.Butaslargescaleelectricenergystorageisnotcosteffective,directgridconnectedwindpoweristhemostviableoption.

Fig.1InstalledcapacityandnetgenerationofwindpowerinUS

Similartoothergenerationprocesses,awindturbineconvertsmechanicalenergyintogeneratortorqueandthegeneratorconvertsthistorqueintoelectricityandfeedsitintothegrid.Thedifferenceisthatthemechanicalenergyisfromwind.Awindturbineisacomplexsystembecausetheknowledgefromtheareasofaerodynamicsandmechanical,electrical,andcontrolengineeringisapplied.Tomakethewindturbinesmoreefficientandmatchthegridrequirementsbetter,moreandmoretechnologiesarebeingappliedtothem.TherearecurrentlythreemaintypesofwindturbinesavailableasshowninFig.2:

（a）Fixedspeedwindturbinewithanasynchronoussquirrelcageinductiongenerator（IG）directlyconnectedtothegridviaatransformer.

（b）Variablespeedwindturbinewithadoublyfedinductiongenerator（DFIG）andbladepitchcontrol.

（c）Variablespeedwindturbineusingapermanentmagnetsynchronousgeneratorthatisconnectedtothegridthroughafull-scalefrequencyconverter.Thisiscalleddirectdrive（DD）windturbine.

Withtheapplicationofnewtechnologies,thecostofelectricityfromutility-scalewindsystemshasdroppedbymorethan80%overthelast20years.Now,state-of-the-artwindpowerplantsatexcellentsitesaregeneratingelectricityatlessthan5cents/kWh,whichisactualcostwithoutothereconomicbenefitssuchasproductiontaxcredit[2].Comparedtothecostsofconventionalgenerationtechnologies,itisveryattractiveandnootherresourcesareneededtodealwithexpensivepollutionemissioncontrolequipments.

（a）

（b）

（c）

（a）Fixedspeedwindturbinewithaninductiongenerator

（b）Variable-speedwindturbinewithadoubly-fedinductiongenerator

（c）Variable-speedwindturbinewithapermanentmagnetsynchronousgenerator

Fig.2Generalstructuresofthreedifferenttypesofwindturbines

Windpowerwillbelookedatassameasacommonelectricalenergyresourceeventually,sotheassociatedrequirementsofconventionalgenerationtechnologies,suchaspowerfactorcorrection,supplyingreactivepowertothetransmissionsystem,stabilityimprovementandsoon,arebeingincreasinglyappliedtowindturbines.Whichtypeofwindturbineshouldbeselectedforaparticularwindfarmprojectisbecomingoneofthekeyissuesinthedecisionmakingprocess.Thispaperintroducesthecharacteristicsoftheabovementionedthreetypesofwindturbinesandpresentstheirmathematicalmodels.Computersimulationsoftheirresponsestoaseverethree-phasetogroundfaultattheendofatransmissionlinearepresented.Finallytheyarecomparedanddiscussedfrombothtechnicalandeconomicpointsofview.

II.BACKGROUND

Althoughutilizationofwindpowerisincreasingveryfastintheworldandthecostisdecreasingrapidly,themainchallengesare:

therelativelyhighcostofproducingakWh,thereductionofcapitalcostofthewindturbineitself,andimprovingreliability.

Fromtheviewofwindturbinedesignandmanufacture,thecostofIGisthelowestbecausenopowerelectronicsdevicesareused.Thevoltagesagintheprocessofsinglephasefaultislowinthistypeofgenerator.Butitsdisadvantagesare:

itcannotruninwindgust,efficiencyislow,anditcannotcontrolreactivepoweroutput,whichisaveryimportantrequirementforpowersystemvoltagestabilityandquality.ThisiswhyIGisdisappearingfromthecurrentmarkets.

ComparedtoIG,whichisconnectedtothegriddirectly,indirectgridconnectedwindturbines（includingwindturbineswithDFIGandDD（directdriver））aremuchmoreefficientbecausetheycouldberunatvariablespeed.Furthermore,indirectgridconnectedwindturbinescancontrolreactivepowertoimprovepowerqualityfortheelectricalgrid.Thisadvantageisespeciallyusefulforaweakelectricalgrid,averycommonoccurrenceaswindfarmsaretypicallylocatedatremotelocations.Thisiswhyindirectgridconnectedwindturbinesarewidelyusedcurrentlyinspiteoftheirhighinitialcostsandcomplexcontrolstrategies.

However,indirectgridconnectedwindturbinesstillneedmanyimprovementstocompetewithotherconventionalelectricitygenerationtechnologies.Firstly,asFig.2shows,theindirectgridconnectedwindturbineswillneedarectifierandtwoinverters,onetocontrolthestatorcurrent,andanothertogeneratetheoutputcurrent.Thesepowerelectronicsdevicescost14%oftotalinitialprojectcapitalcosts[5],butitmaychangeasthecostofpowerelectronicsdecreases.Secondly,thereareenergylossesassociatedwithAC/DC/ACconversionprocess,andharmonicdistortionsofthealternatingcurrentmaybeintroducedintheelectricalgridbypowerelectronicsdevices,thusreducingpowerquality.

Toimprovetheperformanceofwindturbines,differenttechnologiesarebeingappliedtothem.Nowtwotypesofindirectgridconnectedwindturbinesdominatethemarket.TheDDtypeofwindturbinesismainlybuiltbyEnercon（Germany）.ThistypeofwindturbinesiscombinedwithsynchronouspermanentmagnetgeneratorandAC/DC/ACconverterwitharatingof100%oftheratedwindturbinepower.Sinceitdoesnotneedthegearbox,theweightatthehubheightcanbeloweredalot,andtheoperationandmaintenanceofthegearboxarenotneeded.Butbecausethecapacityoftheconverterhastomatchthemaximumoutputpowerofthegenerator,itscostishighestamongalltypesofwindturbines.Alsothegeneratorisbiggerthanothertypesofwindturbines.Inthelongterm,theoperationandmaintenancecostsofthegearboxcanbesaved.

TheothertypeofindirectgridconnectedwindturbineisavariablespeedwindturbinewithDFIG,whichdominatesthemarketwiththeirtotalsharetobearound84.5%-86%.ThewindturbinewithDFIGiscombinedwithgearbox,inductiongenerator,andAC/DC/ACconverterwitharatingofonly20%–30%oftheratedwindturbinepower..ThecostofDFIGsystemislowerthanthedirectdrivesystembecauseitspowerconverterisapproximatelyone-thirdthesizeofthedirectdrivesystem.ButthecontrolsystemofaDFIGismorecomplexthanthatofaDD.

III.MODELING

A.Blademodeling（windmodeling）

Anaerodynamicmodelofthewindturbinesisacommonpartofthedynamicmodelsoftheelectricity-producingwindturbines.Thecapturedaerodynamicpowerisgivenby:

wherePisthecapturedpowerfromwind,ρistheairdensity,visthewindspeed,Aisthesweptareaoftheblade,C（λ）isthepowercoefficient,λistheratiobetweenbladetipspeedandwindspeedathubheight,θisthepitchangle.C（λ,θ）canbeobtainedfromwindturbinemanufacturers.

B.Drivetrainmodeling

Themechanicalconstructionofthewindturbinesissimplymodeledasalumped-masssystemwiththelumpedcombinedinertiaconstantoftheturbinerotorandthegeneratorrotor.Theshaftdynamicequationis:

whereJTandJGaretheinertiaconstantoftheturbinerotorandthegeneratorrotor,respectively,KsandDsaretheshaftstiffnessanddampingconstantrespectively,angularspeed,θTGistheelectricaltwistangleoftheshaft.ωTandωGaretheangularspeedsofshaftattheendsofturbineandgenerator,respectively,TTandTEarethemechanicalandelectricaltorque,respectively.

C.Generatormodeling

Asmentionedearlier,therearethreetypesofgeneratorsusedinwindturb