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Analysis and simulation of high frequency link converters as a power flow controller in flexible AC power transmission systems PDF

197 Pages·1992·6.4 MB·English
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Preview Analysis and simulation of high frequency link converters as a power flow controller in flexible AC power transmission systems

ANALYSISANDSIMULATIONOF HIGHFREQUENCYLINKCONVERTERSASAPOWERFLOWCONTROLLER INFLEXIBLEACPOWERTRANSMISSIONSYSTEMS By GYO-BUMCHUNG ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT OFTHEREQUIREMENTSFORTHEDEGREEOF DOCTOROFPHILOSOPHY UNIVERSITYOFFLORIDA 1992 UNIVERSITYDFFLORIDALIBRARIES Tomylovingwife,Bo-Young ACKNOWLEDGEMENTS I would like to express my deepest gratitude to my advisor and committee chairman,Dr.DennisP.Carroll,forhisguidance,encouragementandsupport.Iwould alsoliketothankotherprofessors,Dr.A.Domijan,Dr.J.Watson,Dr.K.NgoandDr. B.Capehartforservingonmysupervisorycommittee. IamgratefultoDr. Ngoforhishelpfuldiscussions.IamalsogratefultoDr. WatsonandDr.CapehartforhelpingmetoimprovemyskillinEnglish.Appreciation isowedtoTeresaLeeandSteveSwindlerfortheireditorialhelp; toSung-WonKo, Chie-TeukAhn, Taek-WonJeongand Sung-HoonParkfortheirencouragementand moralsupport. Iwouldliketothankmyparents,parentsin-laws,brothersandsistersfortheir sincere support. Specially, I can never thank my wife, Bo-Young, enough for her patienceandsacrifice.Thanksalsogotomydaughter,Su-Kyung,whohasgivenvitality tome.Iwouldalsoliketothankeverybodyelsewhoencouragedme. This work was partially supported by Project RP4000-19 ofElectric Power ResearchInstitute. 111 TABLEOFCONTENTS ACKNOWLEDGEMENTS iii LISTOFSYMBOLS vi ABSTRACT viii CHAPTERS 1 INTRODUCTION 1 1.1 Background 1 1.2 Objective 8 1.3 Overview 8 2 HIGHFREQUENCYLINKCONVERTER 11 2.1 StructureofHighFrequencyLinkConverter 11 2.2 ZeroVoltageSwitchingandPulseDensityModulation ... 15 2.3 TankCircuitDesign 21 2.4 InductiveFiltering 27 2.5 SwitchingDeviceandCommutationMethod 28 3 TOPOLOGIES OF VARIOUS HIGH FREQUENCY LINK CONVERTERS 34 3.1 HFLCCycloconverter 34 3.2 HFLCSeriesCompensator 39 3.3 HFLCPhaseShifter 43 3.4 HFLCShuntCompensator 47 4 MODELING OF HIGH FREQUENCY LINK CONVERTER CONTROLLERS 53 4.1 CurrentReferenceWaveformPDMControl 54 4.2 ComparisontoOtherMethods 58 IV 4.3 PowerFlowControl 62 4.3.1 HFLCCycloconverter 67 4.3.2 HFLCSeriesCompensator 68 4.3.3 HFLCPhaseShifter 69 4.4.4 HFLCShuntCompensator 70 4.4 TankVoltageControl 71 4.5 High-LevelControlSystem 75 5 SIMULATIONANDRESULTS 83 5.1 TestACPowerSystem 84 5.2 Steady-State Performance of HFLCs in Simple Test System 88 5.3 HarmonicAnalysisofSteady-StateOutputofHFLCs ... 100 5.4 TransientAnalysisofHFLCsinASimpleTestSystem . . 108 5.5 VersatileControlCapabilityofHFLCs 119 5.6 HFLCsOperationinFloridaPowerandLightSystem . . 127 5.7 HFLCsOperationduringACSystemFaults 135 6 CONCLUSIONANDFUTURERESEARCH 143 APPENDICES A MEASUREMENTALGORITHM 146 B CIRCULATINGPOWERFLOWANALYSIS 150 C DESIGNOFTANKVOLTAGECONTROLLER 153 D LOADFLOWANALYSISOFFP&LSYSTEM 163 E EMTPINPUTDATAFILEOFFP&LSYSTEM 166 F HARMONICANALYSISOFOUTPUTSOFHFLC CYCLOCONVERTER 175 G DESIGNOFCAPACITANCEOFTHETANKCIRCUIT 177 REFERENCES 181 BIOGRAPHICALSKETCH 186 v LISTOFSYMBOLS L,j:Transmissionlineinductanceplusfilterinductance Lf:Filterinductance L,:Transmissionlineinductance X:Transmissionlineimpedance 1^:Tankcircuitinductance Ct:Tankcircuitcapacitance fh:Frequencyofthetankcircuit f,:Frequencyoftheacsystem GO):Theangularvelocityoftheacsystem ojj,:TheangularvelocityofthetankcircuitofHFLC Vt:Tankvoltage V,,,:Thepeakvalueoftankvoltage Ist:Theexternalcurrentflowingintothetankcircuit Istp:Thepeakvalueoftheexternalcurrent,I8t. Vu:Line-to-linevoltageatHFLCoutputterminal V,:LinevoltageatHFLCoutputterminal Vm:Magnitudeofthelinevoltage I[:Linecurrent vi I,,,:Magnitudeofthelinecurrent S:Theinstantaneouspowerflow P,:Realpowerflowfromsystem1 P2:Realpowerflowtosystem2 P,:Realpowerflowfromacsystemtotankcircuit Pi,,:Realpowerflowfromacpowersystemtotankcircuitthroughinputconverter Qj:Reactivepowerflowfromsystem1 Q2:Reactivepowerflowtosystem2 Q,:Reactivepowerflowfromacsystemtotankcircuit Qm:Reactivepowerflowfromacpowersystemtotankcircuitthroughinputconverter W c:Energystoredintankcircuitfortheprevioushalfcycleoftankvoltage W,:Energystoredintankcircuitforthepresenthalfcycleoftankvoltage 0:Phaseangleoflinevoltage 5:Phaseangledifferencebetweenthelinevoltages 6:Thephaseanglebetweenvoltageandcurrent. AV:The60HzcomponentoftheoutputvoltagesynthesizedattheterminalofHFLC AW:Therippleofthetankenergy AIm:Thesmallchangeofthelinecurrentinlinearization A6:Thesmallchangeofthephaseangleoflinecurrentinlinearization AV,:Therippleofthetankvoltage AP:Thesmallchangeoftherealpowerflowinlinearization AQ:Thesmallchangeofthereactivepowerflowinlinearization Vll AbstractofDissertationPresentedtotheGraduateSchool oftheUniversityofFloridainPartialFulfillmentofthe RequirementsfortheDegreeofDoctorofPhilosophy ANALYSISANDSIMULATIONOF HIGHFREQUENCYLINKCONVERTERSASAPOWERFLOWCONTROLLER INFLEXIBLEACPOWERTRANSMISSIONSYSTEMS By GYO-BUMCHUNG May1992 Chairman:ProfessorD.P.Carroll MajorDepartment:ElectricalEngineering Thisdissertationinvestigatesthefeasibilityofthehighfrequencylinkconverter (HFLC)asapowerflowcontrollerinaflexibleacpowertransmissionsystem(FACTS). TheHFLChasasingle-ungrounded,parallel-resonanttankcircuit,switchingdevices,and acurrentreferencewaveformpulsedensitymodulation(CRWPDM)controlleremploying zero-voltageswitchingtoreduceswitchingloss. ItisshownthattheHFLCcanserveasaHFLCcycloconverter,aHFLCseries compensator,aHFLCphaseshifteroraHFLCshuntcompensatorinordertocontrol thepowerflowaccuratelyandquicklyintheacpowertransmissionsystem.Thecontrol systemofeachHFLCapplicationwasdeveloped.Inordertoevaluatetheperformance ofHFLC’s as power flow controllers in ac power transmission systems, complete computersimulationmodelsoftheHFLC’susingElectro-MagneticTransientsProgram (EMTP)weredeveloped.ThecomputersimulationmodelsincludetheHFLCcircuit,the controlsystem,themeasurementsystemandtheacpowertransmissionsystemtoform integratedtestmodels.Asimpletwo-busone-branchacpowertransmissionsystem,and V1U a13-busreducedmodeloftheFloridaPowerandLight(FP&L)500KVtransmission systemwereusedasacpowersystemmodels. The following characteristics were evaluated by theEMTP simulation study: steady-stateperformance,transientperformance,harmonicsandfilteringrequirements, thecontrolofHFLC’sinthesimpleacpowersystemandthedampingeffectandthe protectionofHFLC’sinFP&Lsystem.ComparisonsbetweenHFLC’swerealsomade. PotentialproblemareaswereidentifiedforsuccessfulimplementationofHFLC’sasthe powerflowcontrollerinFACTS. IX CHAPTER1 INTRODUCTION Onepotentialcandidateas a flexibleacpower transmission system (FACTS) elementisahighfrequencylinkconverter(HFLC).Thisstudyinvestigatethefeasibility ofthe5 KHzHFLCinordertoimprovetheperformanceofthe500KVacpower transmissionsystem.TheHFLCcircuitcanserveasaHFLCcycloconverter,aHFLC seriescompensator,aHFLCphaseshifteroraHFLCshuntcompensatorinanacpower transmission system. The study includes theanalysis, the design, and the computer simulationofHFLCanddemonstratesFACTSconceptsusingHFLCinapracticalac powertransmissionsystem.ThecontrolsystemofeachHFLCisdevelopedtocontrol thepowerflowinanacpowersystem.TheElectro-MagneticTransientProgram(EMTP) isusedasatoolofthecomputersimulationstudyofHFLC. 1.1Background Powerflowsinaconventionalacpowertransmission system cannoteasilybe directedalongspecific,desiredpathsbychangingthemagnitudeofthenodevoltageor byshiftingthephaseofthenodevoltage. Asaresult, acpowertransmission system suffers from parallel-path orloop flows [4]. Mostofthe devices now available for improvingacpowertransmissionsystemperformance,suchasaphase-shiftingortap- changingtransformer, aremechanicallyswitched. However, inmechanicallyswitched 1

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