Table Of ContentANALYSISANDSIMULATIONOF
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
