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文献翻译

南昌工程学院

07级毕业（设计）文献翻译

机械与电气工程系（院）电气工程及其自动化专业

题目某企业110kV降压变电站电气部分设计

学生姓名靳占利

班级07电气工程及其自动化

（1）班

学号2007100056

指导教师范莉

日期年月日

南昌工程学院教务处订制

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指导教师：

年月日

Onsomeofthedesignaspectsofwindenergyconversionsystems

Abstract

Intheoverallprocessofutilizingwindpower,twoessentialcomponentsoftechnicaldata,i.e.onerelatedtotheengineeringorperformancecharacteristicsofcommerciallyavailablewindturbinegenerators,andtheotherrelatedtotheavailabilityofwindresources,areneed.Theperformanceofwindenergyconversionsystems（WECs）dependsuponsubsystemslikewindturbine（aaerodynamic）,gears（mechanical）,andgenerator（electrical）,Theavailabilityofwindresourcesisgovernedbytheclimaticconditionsoftheregion,forwhichthewindsurveyisextremelyimportanttoexploitwindenergy.Inthispaper,designaspects,suchasfactoraffectingwindpower,sitingrequirementsforWECs,problemsrelatedwithgridconnections,classificationofwindelectricgenerationschemes,criteriaforselectionofequipmentforWECs,choiceofgenerators,threebasicdesignphilosophies,mainconsiderationsinwindturbinedesign,choicebetweentwoandthreebladerotors,weightandsizeconsiderationsandenvironmentalaspectsrelatedwithWECshavebeenpresented.

1.Introduction

Windpoweredsystemshavewidelyusedsincethetenthcenturyforwaterpumping,grindingandotherlowpowerapplication.Therewereseveralearlyattemptstobuildlargescalewindpoweredsystemstogenerateelectricity.In1931,theRussiansbuiltalargewindmillwitha100ft（30.5m）diameterblade,butithadaverylowconversionefficiencyandwasabandoned.In1945,aVermountutilitybuiltalargewindpoweredgeneratortoproduceelectricity.Thissystemcosted$1.25millionandhadanelectricalpoweroutputof1.25MW.Thisunitlastedfor23daysbeforeoneofthebladesfailedduetofatigue,andtheprojectwasabandoned.

TheNationalAeronauticsandSpaceAdministration（NASA）,inconjunctionwiththeEnergyResearchandDevelopmentAdministration（ERDA）,hasbuiltandtestedalargenumberoflargewindpoweredgenerators.Thefirstmachinewasa100KWunitbuiltatSandusky,Ohio,foraroundamilliondollars.Anumberofothermachineswithpowerupto2.5MWandrotordiameterupto350ft（107m）havebeenconstructed.Duringthe1980s,itbecamepopulartoinvestmoneyinwindsystemsbecauseofthetaxbenefits.Consequently,anumberofwindfarmswerebuilt,particularlyinthemountainpassesofCalifornia.In1985,abouthalfoftheworld’swindgeneratedelectricitywasproducedintheAltamountPasseareaofCalifornia.Thisareahas6700turbineswithatotalratedcapacityof630MW.Amongtherenewablesourcesoffenergyavailabletodayforgenerationofelectricalpower,windenergystandsforemostbecauseoftherelativelylowcapitalcostinvolvedandtheshortgestationperiodrequired.Theworldhasobtainedtheinstalledwindcapacityof13400MWbytheendof1992.

Thedesignandsuccessfuloperationoflargescalewindpoweredgeneratorsfaceanumberofformidableproblems.Ifthesystemisdesignedtoproducea.cpower,aconstantangularvelocityandforceproblems.Unfortunately,thewindvelocityisneitherconstantinmagnitudeordirectionnorisitconstantfromthetoptobottomofalargerotor.Thisimposesseverecyclicloadsontheturbineblades,creatingfatigueproblems.Thisproblemiscompoundedifadownwindrotorsystemisusedbecausetheshadowofthesupporttowerunloadstheblade.Thiseffectalsoproducesanoticeablenoise,whichcanbeobjectionable.

Theavailablewindresourceisgovernedbytheclimatologyoftheregionconcernedandhasalargevariabilityfromonelocationtotheotherandalsofromseasontoseasonatanyfixedlocation.Alotofdevelopmenthastakenplaceinthedesignofwindenergyconversionsystems.Modernwindturbinesarehighlysophisticatedmachinesbuilt,ontheaerodynamicprinciplesdevelopedfromtheaerospaceindustry,incorporatingadvancedmaterialsandelectronicsandaredesignedtodeliverenergyacrossawiderangeofspeeds.Inthispaper,WECsrelatedaspects,suchasfactorsaffectingwindpower,sitingrequirementsforWECs,criteriaforselectionofequipmentforWECs,choiceofgenerators,threebasicdesignphilosophies,mainconsiderationsinwindturbinedesign,choicebetweentwoandthreebladerotors,weightandsizeconsiderationsandenvironmentalaspectsrelatedwithWECshavebeenpresented.

2.Factorsaffectingwindpower

Oneofthemostimportanttoolsinworkingwiththewind,whetherdesigningawindturbineorusingone,isthefirmunderstandingofthefactorsaffectingthewindpower.Followingaretheimportantfactorsthatmustbeconsidered:

2.1.Windstatistics

Windisahighlyvariablepowersource,andthereareseveralmethodsofcharacterizingthisvariability.Themostcommonmethodisthepowerdurationcurve.ThisisagoodconceptbutisnoteasilyusedtoselectVcandVrforagivenwindsite,whichisanimportantdesignrequirement.Anothermethodistouseastatisticalrepresentation,particularlyaWeibullfunction.

2.2.Loadfactor

Thereareatleasttwomajorobjectivesinwindturbinedesign.Oneistomaximizetheaveragepoweroutput.Theotheristomeetthenecessaryload（whichistheratioofaverageelectricalpowertotheratedelectricalpower）requirementoftheload.Loadfactorisnotofmajorconcernifthewindelectricgenerator（WEG）isactingasafuelsaverontheelectricnetwork.Butifthegeneratorispumpingirrigationwaterinasynchronousmode,forexample,theloadfactorisveryimportant.

2.3.Seasonalanddiurnalvariationofwindpower

Seasonalanddiurnalvariationshavesignificanteffectsinwind.Loaddurationdataarerequiredtojudgetheappropriateeffects.Diurnalvariationislesswithincreasedheight.Averagepowermayvaryfromabout80%ofthelongtermannualaveragepowerintheearlymorninghourtoabout120%ofthelongtermaveragepowerintheearlyafternoonhours.

2.4.Variationwithtime

Formostapplicationsofwindpower,itismoreimportanttoknowaboutthecontinuityofsupplythanthetotalamountofenergyavailableinayear.Inpractice,whenthewindblowsstrongly,e.g.morethan12m/s,thereisnoshortageifpower,andoften,thegeneratedpowerhastobedumped.Difficultiesappear,however,ifthereareextendedperiodsoflightorzerowinds.Aruleofthumbforelectricitygenerationisthatsiteswithaveragewindspeedlessthan5m/swillhaveunacceptablylongperiodswithoutgeneration,andthesitesofaverage8m/sorabovewillbeconsideredverygood.Inallthecasesitwillbenecessarytomatchcarefullythemachinecharacteristictothelocalwindregimetogivethetypeofsupplyrequired.

3.SitingrequirementsforWECs

Inadditiontoadequateavailabilityofwindresources（aminimumof18km/hor5km/hwindspeed）thefollowingfactorshavetobeconsideredwhilelocatingaWEG:

a.availabilityofland,

b.availabilityofpowergrid（foragridconnectedsystem）,

c.accessibilityofsite,

d.terrainandsoil,

f.frequencyoflightningstrokes.

Oncethewindresourceataparticularsitehasbeenestablished,thenextfactortobeconsideredistheavailabilityofland.Theareaoflandrequireddependsuponthesizeofwindfarm.Theoptimumspacinginarowis8-12timestherotordiameterinthewinddirectionsand1.5-3timestherotordiameterincrosswinddirections.Asaruleofthumb,10ha/MWcanbetakenasthelandrequirementofwindfarms,includinginfrastructure.Inordertooptimizethepoweroutputfromagivensite,additionalinformationisneeded,suchaswindrose,windspeeds,vegetation,topography,groundroughnessetc.,besidestheconfigurationofasetofwindturbines,whichcanbealteredforreachingbestarrayefficienciesandhighestgeneration.Factorssuchasconvenientaccesstothewindfarmsite,loadbearingcapacityofthesoil,frequencyofcyclones,earthquakesetc.,alsorequireconsiderationbeforesitingthewindfarm.

4.Choiceofgenerators

Therearemainlythefollowingthreeclassesofgenerators:

4.1.DCgenerators

DCgeneratorsarerelativelyunusualwind/micro-hydroturbineapplicationsbecausetheyareexpensiveandrequireregularmaintenance.Nowadays,formostd.c.applications,forexample,itismorecommontoemployana.c.generatortogeneratea.c.,whichisthenconvertedtod.c.withsimplesolidstaterectifiers.

4.2.Synchronousgenerator

Themajoradvantageofsynchronousgeneratoristhatitsreactivepowercharacteristiccanbecontrolled,andthereforesuchmachinescanbeusedtosupplyreactivepowertootheritemsofpowersystemsthatrequirereactivepower.Itisnormalforastandalonewind-Dieselsystemtohaveasynchronousgenerator,usuallyconnectedtotheDieselengine.Synchronousgenerators,whenfittedtoawindturbine,mustbecontrolledcarefullytopreventtherotorspeedacceleratingthroughsynchronousspeedespeciallyduringturbulentwinds.Moreover,itrequiresaflexiblecouplinginthedrivetrain,ortomountthegearboxassemblyonspringsordamperstoabsorbturbulence.Synchronousgeneratorsarecostlierthaninductiongenerators,particularlyinsmallersizeranges.Synchronousgeneratorsaremorepronetofailures.

4.3.Inductiongenerators

Aninductiongeneratoroffersmanyadvantagesoveraconventionalsynchronousgeneratorasasourceofisolatedpowersupply.Reducedunitcost,ruggedness,brushless（insquirrelcageconstruction）,reducedsize,absenceofseparateDCsourceandeaseofmaintenance,self-protectionagainstsevereoverloadsandshor