英语原文.docx

英语原文.docx

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英语原文

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IEEETRANSACTIONSONSUSTAINABLEENERGY,VOL.4,NO.1,JANUARY201331AMethodologyforTransforminganExistingDistributionNetworkIntoaSustainableAutonomousMicro-GridM.VenkataKirthiga,S.ArulDaniel,Member,IEEE,andS.GurunathanAbstract-Adistributionnetworkwithrenewableandfossil-basedresourcescanbeoperatedasamicro-grid,inau-tonomousornonautonomousmodes.Autonomousoperationofadistributionnetworkrequirescautiousplanning.Inthiscontext,adetailedmethodologytodevelopasustainableautonomousmicro-gridispresentedinthispaper.Theproposedmethodologysuggestsnovelsizingandsitingstrategiesfordistributedgener-atorsandstructuralmodificationsforautonomousmicro-grids.Theoptimalsitesandcorrespondingsizesofrenewableresourcesforautonomousoperationareobtainedusingparticleswarmop-timizationandgeneticalgorithm-basedoptimizationtechniques.Structuralmodificationsbasedonrankingofbuseshavebeenat-temptedforimprovingthevoltageprofileofthesystem,resultinginreductionofrealpowerdistributionlosses.Theproposedmethodologyisadoptedforastandard33-busdistributionsystemtooperateasanautonomousmicro-grid.Resultsconfirmtheusefulnessoftheproposedapproachintransforminganexistingradialdistributionnetworkintoanautonomousmicro-grid.IndexTerms-Distributedpowergeneration,loadflow,powergenerationplanning.NOMENCLATURERealpowerratingofthethgenerator.Maximumgenerationlimitonthethgenerator.Minimumgenerationlimitonthethgenerator.Reactivepowerratingofthethgenerator.Costcoefficientoftherenewableenergysourceatthethbus.Currentdrawnfromthesubstationfeeder.Realpowerlossinlinebetweenbusesand.Totalrealpowergeneratedinthesystem.Totalreactivepowergeneratedinthesystem.ManuscriptreceivedOctober20,2011;revisedFebruary06,2012;accepted.April16,2012DateofpublicationMay30,2012;dateofcurrentversionDe-cember12,2012.MVKirthigaandSADanielarewiththeDepartmentofElectricalandElectronicsEngineering,NationalInstituteofTechnology,Tiruchirappalli620015,India（e-mail:

mvkirthiga@nitt.edu;daniel@nitt.edu）.S.GurunathanwaswithDepartmentofElectricalandElectronicsEn-gineering,NationalInstituteofTechnology,Tiruchirappalli,India,andis.nowwithWEGIndustriesofIndia（P）Ltd,Hosur635109,India（e-mail:

guru_gce2005@yahoo.co.in）.Colorversionsofoneormoreofthefiguresinthispaperareavailableonlineathttp:

//ieeexplore.ieee.org.DigitalObjectIdentifier10.1109/TSTE.2012.2196771Maximumlimitonthebusvoltagemagnitude.Minimumlimitonthebusvoltagemagnitude.Magnitudeofthevoltageatthethbus.Maximumbusvoltagemagnitudeatthbusofthesystem.Minimumbusvoltagemagnitudeatthethbusofthesystem.,Totalrealpowerdemandinsummerandwinter,respectively.,Totalreactivepowerdemandinsummerandwinter,respectively.Numberofbusesinthedistributionsystem.Numberofdistributedgenerator（DG）locations（Sites）.I.INTRODUCTIONINmodernpowerdistributionsystems,integratingsmallnonconventionalgenerationsourceshasbecomeattractive.Thesetechnologieshavelessenvironmentalimpact,easysiting,highefficiency,enhancedsystemreliabilityandsecurity,improvedpowerquality,loweroperatingcostsduetopeakshaving,andrelievedtransmissionanddistributioncongestion[1].Thedistributedgenerator（DG）unitsusedarehighlymodularinstructureaswellashelpfulinprovidingcontinuouspowersupplytotheconsumers.However,dependingontheratingandlocationofDGunits,thereisalsoapossibilityforvoltageswellandanincreaseinlosses.Inthisscenario,toexploitthecompletepotentialofdistributedgeneration,propersitingandsizingofDGsbecomeimportant.Thispaper,there-fore,attemptstodevelopasizingalgorithmthattransformsanexistingdistributionnetworktoasustainableautonomoussystem.Insuchanoperation,thegenerationandcorrespondingloadsofthedistributionnetworkcanseparatefromthefeedernetworkandformamicro-gridwithoutaffectingthetransmis-siongrid'sintegrity.Mostofthecurrentmicro-gridimplementationscombineloadswithsourcesplacedatfavorablesitesthatallowinten-tionalislandingandtrytouseutmosttheavailableenergy[2].Insuchanoperation,stablegenerationandvoltageprofilearenecessarytoindependentlysupplypowertocustomers[3].1949-3029/$31.00©2012IEEE

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32IEEETRANSACTIONSONSUSTAINABLEENERGY,VOL.4,NO.1,JANUARY2013Henceobtainingthenumberoflocations（sites）atwhichtheDGsareplacedbecomessignificant.Inearlierworks,algorithmsweredevelopedforoptimalsizingoftheDGunitsandtheypertaintononautonomousmodeofoperationofthemicro-grids.Haesenetal.proposedasizingalgorithmbasedonminimizingthelossesusinggeneticalgorithm（GA）[4].MallikarjunaproposedanotheralgorithmbasedonsimulatedannealingforoptimizingthesizeoftheDGsinamicro-grid[5].Optimalsizingbasedonthedetailedannualizedcostcalculationswasalsoproposed[6].Neverthe-less,noneoftheabovealgorithmshadconsideredautonomousoperationofthemicro-grids.Katiraeietal.Hasdiscussedabouttheautonomousopera-tionofmicro-gridsbutitpertainstoisolatedoperationofafewloadsonemergencyoperatingconditions[7].Liu[8]andNehrir[9]havealsohighlightedisolatedoperationofhybridrenewablesystems.Butalltheseearlierworksdonotinvesti-gateanyautonomousmicro-gridforalargerdistributionnet-workatmediumvoltagelevel,independentoftheutilitygrid.Sofar,amethodologyforoptimalsitingandsizingoftheDGsinanautonomousmicro-gridisnotreportedintheliterature.Inthiscontext,thispaperattemptstodevelopasizingalgo-rithmforanautonomousoperationofanexistingradialdistribu-tionnetwork,thusmakingitanisolatedsustainablemicro-grid.Theconstraintsincludedintheproposedsizingalgorithmarevoltagelimits,demand,andgeneratorratinglimits.Inadditiontosizing,thispaperfocusesonsitingoftheDGsandsuggestsaminimum-lossconfigurationforthenetwork.Therearemanyoptionsavailableforreducinglossesatthedis-tributionlevel:

reconfiguration,capacitorinstallation,loadbal-ancing,andintroductionofhighervoltagelevels[10],[11].Nevertheless,aheuristicapproachinchoosingthesitesfortheDGunitshasbeenattemptedinthispaperforautonomousmicro-grids.SouzaRibeiroetal.proposedanarchitectureforisolatedmicro-grids[12].Theyhaveproposedprogrammedswitchingofalreadyexistingswitchestoreconfigurethedistributionnetworkforstableoperationasmicro-grid.Twotypesofswitchesareusedinprimarydistributionsystemsviz.,sectionalizingswitches（normallyclosed）andTIEswitches（Normallyopen）[13],[14].Theseswitchesaredesignedforbothprotectionandconfigurationmanagementresultingincostminimization.OptimalreconfigurationofdistributionsystemswithDGshavealsobeendiscussedintheliterature[15]-[18]butcomplexoptimizationtechniqueshavebeenusedtoiden-tifytheoptimallocationofTIEswitchestoenableadditionalbranchesforreconfiguration.Moreover,noneoftheseworksonreconfigurationhadanobjectiveofautonomousoperationofadistributionnetworkasamicro-grid.Inthiscontext,reconfigurationofanexistingdistributionsystemhasalsobeenattemptedforperformanceimprovementofanautonomousmicro-grid.Rankingofthebusesbasedonmaximumloadablelimits（beyondwhichthevoltagelimitsviolationofbuseswasobserved）hasbeenemployedtoidentifythenodes.Basedonthisranking,additionalTIEbranchesaretobeconnected.Thestandard33-busdistributionsystemisusedforvalida-tionofthealgorithmsproposedandMATLABcodinghasbeendevelopedforimplementationoftheproposedalgorithm.Therestofthepaperisorganizedasfollows:

Methodologyforplanninganautonomousmicro-gridisrevealedinSectionII.OptimalsizingofDGsandtheoptimizationtechniquesusedareexplainedinSectionIII.SectionIVfocusesonthesignif-icanceofreconfigurationintheoperationofanautonomousmicro-grid.SectionVdepictsdiscussionsontheresultsinsup-portoftheproposedmethodologyanditsvalidation.Conclu-sionsofthepaperarepresentedinSectionVI.II.PLANNINGOFAUTONOMOUSMICRO-GRIDSItisevidentthattransformationofanexistingradialdistribu-tionsystemintoasustainableautonomousmicro-grid,requiresDGstobeintegratedintothenetwork.Theexactsizeofthesegeneratorsandtheoptimalplacementofthesameinthenet-workarenecessaryforitsautonomousoperation.Henceahi-erarchicalandpartiallyheuristicmethodologyisattemptedfordeterminingtheoptimalsitesandsizesofthegeneratorsandforreconfiguringthenetwork.A.OptimalNumberandLocationofDGUnitsItismandatorythatthetotaldemandandthesystemlossesneedtobesatisfiedbytheDGunitsconnectedtothedistribu-tionsystem.ForobtainingtheoptimalnumberofDGunitsandthecorrespondingsitesfortheDGplacements,thefollowingmethodologyisproposed.1）Anoptimizationproblemisformulatedforminimizingthedistributionlosses,includingtheconstraintsviz.,gener-atorratingconstraint,voltageconstraint,andpowerbal-anceconstraint.2）For""generatorunits,thenumberofdifferentpossiblecombinationsofsitesis,Whereisthetotalnumberofbusesinthedistributionsystem.3）Theparticleswarmoptimization（PSO）techniqueisthenemployedforminimizingtheoptimizationproblem,foreachofthecombinations,whereinitially""issetto1.4）Theoptimallocationscorrespondingtoth