大功率变流技术Project1 SPWM Control Schemes for TwoLevel Voltage Source Inverter.docx
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大功率变流技术Project1SPWMControlSchemesforTwoLevelVoltageSourceInverter
PowerConversionSystems
SPWMControlSchemesforTwo-LevelVoltageSourceInverter
PengJiaqiao,3130104084,1056607357@
Abstract-Voltagesourceinverterhasbeenwidelyusedinmodernindustrywithaveryimportantposition. Intheprocessofobtainingbetterequipmentandsystemperformance,howtochangethecontrolmethodandcircuitparameterstoreducetheTHDisveryimportant. Thereportcanbedividedinthreeparts. Thefirstpart,thecircuitinductance,impedance,andothercomponentparametersaredesignedinaccordancewiththerequirements.Thesecondpart,byregulatingdifferentvoltageamplituderatiocircuitTHDchangeswillbeobserved. Thethirdpart,injectthirdharmonicmodulationcircuittoobservetherelationshipoftheamplitudemodulationratioandcircuitTHD. Eachtimethesimulation,thelowharmonicofthecircuitwillalsobeobserved.InPartB,itisseenthattheamplitudemodulationratioincreases,reducingtheoutputvoltageandcurrentTHD,andincreasetheutilizationofthebusvoltage,butatthesameloworderharmonicsalsoincreases. Intheharmonicinjectionplan,whenthethirdharmonicamplitudeisrelativelyhigh,theoutputvoltageandcurrenthasasmallerTHD,alsowithlowharmonic. Thisreportdescribestheprocessandsimulationresultsoftheexperiment.
IndexTerms—SPWM,Two-LevelVoltageSourceInverter,harmonic,THD,commonmodevoltageinjection.
I.Introduction
Voltagesourceinverterhasbeenwidelyusedinmodernlifeinordertomeetthenormalworkofthedifferentelectricalequipment. Thisyear,withtheinventionofthegreatervarietyoftopologies,thevoltagesourceinverterhasbeendevelopedrapidly.Butinthisessaywediscusstwo-levelvoltagesourceinverterbecauseitisoneofthemostcommon.
Sinusoidalpulsewidthmodulation（SPWMmodulation）,inordertogetabetteroutputvoltageandcurrent,thecircuitcontrolschemeisveryimportant. Peoplealwayswantthecircuittohavethehighervoltagebusutilization,fasterresponsetime,lesslowharmonicaswellassmallwaveformdistortion,buttheycannotachieve. Inadifferentcircuitdesign,wemustaccordingtotheneeds
SubmittedData:
Signature:
ofthecircuitoftheaboveperformancetrade-offs. Thenweneedtoknowthedifferentcircuitparametersoncircuitperformance.
SotheauthorusedcomputermodelingTwo-LevelVoltageSourceSPWMInvertercircuitanddosomesimulationwithdifferentparameters.Finallyalotofvaluableconclusionshavebeengotten.Thereportdescribedindetailintheexperimentalproceduresandresults,thefinalsimulationmodel. ThesimulationofthisreportbasedonMatlab/Simulink.
II.PartA
SystemSpecifications
InverterTopology:
Two-levelvoltagesourceinverterasfollow
RatedInverterOutputPower:
1MVA
RatedInverterOutputVoltage:
4160V（fundamentalline-to-linevoltage,rms）
RatedInverterOutputCurrent:
Tobecalculated（fundamental,rms）
RateddcInputVoltage:
Constantdc（tobedetermined）
Load:
RLloadwithaper-phaseresistanceof0.95puandinductanceof0.31pu,whichgivestheloadimpedanceof1.0puwithalaggingpowerfactorof0.95.NotethattheRLloadisfixedfortheinverteroperatingundervariousconditions.
SwitchingDevices:
Idealswitch（nopowerlossesorforwardvoltagedrops）
Basedonthegivensystemspecifications,wecancalculatethecircuitparameters-outputcurrentIo,dcinputVd,loadresistanceandinductance.
Asaresult,
III.PartB
TheauthordevelopedasimulationprogramfortheconventionalSPWMschemeandrunthesimulationprogramforthetasksgivenintheTable1.
Foreachofthetasks,theauthordrawnthewaveforms（twocycleseach）fortheinverterline-to-linevoltageVAB（V）andinverteroutputcurrentiA（A）.Theharmonicspectrum（0to60thharmonics）ofVABnormalizedtothedcvoltageVdandiAnormalizedtoitsratedfundamentalcomponentIA1willalsobegiven.
B.3Analyzeyoursimulationresultsanddrawconclusions.
Table1.SimulationtasksforconventionalSPWMscheme
SimulationTask
f1（Hz）
ma
THD（%）
vAB
THD（%）
iA
T.1
20
0.3
4.02
0.07
T.2
30
0.7
4.53
1.47
T.3
30
1.1
26.70
14.07
T.4
60
0.6
31.15
3.13
T.5
60
0.8
43.23
13.14
T.6
60
1.3
32.68
13.28
T.1f1=20Hz,ma=0.3
（thewaveformofVAB）
（thewaveformofiA）
（theharmonicspectrumofVAB）
（theharmonicspectrumofiA）
T.2f1=30Hz,ma=0.7
（thewaveformofVAB）
（thewaveformofiA）
（theharmonicspectrumofVAB）
（theharmonicspectrumofiA）
T.3f1=30Hz,ma=1.1
（thewaveformofVAB）
（thewaveformofiA）
（theharmonicspectrumofVAB）
（theharmonicspectrumofiA）
T.4f1=60Hz,ma=0.6
（thewaveformofVAB）
（thewaveformofiA）
（theharmonicspectrumofVAB）
（theharmonicspectrumofiA）
T.5f1=60Hz,ma=0.8
（thewaveformofVAB）
（thewaveformofiA）
（theharmonicspectrumofVAB）
（theharmonicspectrumofiA）
T.6f1=60Hz,ma=1.3
（thewaveformofVAB）
（thewaveformofiA）
（theharmonicspectrumofVAB）
（theharmonicspectrumofiA）
Theabovediagramoftheoutputvoltageandcurrentwaveformsissimilartothesinewave,itsharmonicdistortionincreaseasMaincreaseswhenMa<1. WhentheMa>1,thevoltagewaveforminFigurewillhasobviousdistortion.
Andthefrequencyalsoplayanimportantroleaswecanseetheharmonicdistortionisveryunconspicuouswhenf1isverylow.
ByamplificationoftheFourieranalysisofimages,wefoundthattherearenoevenharmonicsinmanyharmonicorder. Excludetheerrorofthesoftwareitself,harmonicinlinewiththefrequencywillbe
2asIsetfcr=2000Hz.
IV.PartC
IModifiedsimulationprogramdevelopedinPartBwithcommonmodevoltageinjectionscheme.
Table2.Simulationtasksforcommonmodevoltageinjectionscheme
SimulationTask
f1（Hz）
ma
THD（%）
vAB
THD（%）
iA
T.1
20
1.0
18.90
13.93
T.2
20
1.2
30.63
15.53
T.3
20
1.3
32.61
16.13
T.4
60
1.0
41.51
12.31
T.5
60
1.2
32.10
12.34
T.6
60
1.3
32.69
12.22
T.1f1=20Hz,ma=1.0
（thewaveformofVAB）
（thewaveformofiA）
（theharmonicspectrumofVAB）
（theharmonicspectrumofiA）
T.2f1=20Hz,ma=1.2
（thewaveformofVAB）
（thewaveformofiA）
（theharmonicspectrumofVAB）
（theharmonicspectrumofiA）
T.3f1=20Hz,ma=1.3
（thewaveformofVAB）
（thewaveformofiA）
（theharmonicspectrumofVAB）
（theharmonicspectrumofiA）
T.4f1=60Hz,ma=1.0
（thewaveformofVAB）
（thewaveformofiA）
（theharmonicspectrumofVAB）
（theharmonicspectrumofiA）
T.5f1=60Hz,ma=1.2
（thewaveformofVAB）
（thewaveformofiA）
（theharmonicspectrumofVAB）
（theharmonicspectrumofiA）
T.6f1=60Hz,ma=1.3
（thewaveformofVAB）
（thewaveformofiA）
（theharmonicspectrumofVAB）
（theharmonicspectrumofiA）
Startingfrom0.1,Ichangedthemagnitudeofthethirdharmonicwith0.1astheinterval.IfocusedonthecorrespondingTHDandfondithasbeenreducedobviouslythoughitwasstillveryhigh.ButthemagnitudefortheminimumTHDofVABwasalwaysnotequaltothatfortheminimumTHDofiAthoughveryclose,whichgavemesometrouble.Andtherewasalsoaninterestingconclusionthatwiththeincreaseofthemagnitudeofthethirdharmonicamplitude,THDfirstdecreasedtoaminimum,andthenincreasedgradually.
V.Conclusion
ThisreportisaboutTwo-levelvoltagesourceinverterandthematlab/simulinksimulation. Thereportisdividedintothreeparts:
PartAdetailedderivationandcalculationatalllevelsofthecircuitparameters.Basedonthis,wecanestablishthecircuitmodelforasoftwaresimulation. InPartB,themodulationofdifferentmagnitudeisworsethanthecircuitperformanceundertheinquirytodrawtherelevantconclusionsofdifferentfrequencycircuitsimulation,incontrasttofurthertheoreticalknowledgepractice.
Reducethetotalharmonicdistortionisthekeytoenhancetheperformanceofthecircuit.Thirdharmonicinjectionprovidesuswithagoodidea. Andexperimentsshowedthattheschemegreatlyimprovestheperformanceofthecircuit.Overshootafterthethirdharmonicinjectedbeenimproved,fromPartCoftheexperiment,weclearlyseethatthethirdharmonicinjection,lowharmonicissignificantlyreduced. However,thisdoesnotmeanthatthethirdharmonicthebiggerthebetter,thegreatertheinjectionwillalsoincreasetheTHD,andwhat’sworse,thedifficultyoffilterfiltering. Therefore,continuousexperimentationtoseekacompromiseplan.
Infact,doingexperimentsinthelaboratorytotestthemostsuitableparameterwillspendalotoftimeandmoney.Butbasedonmatlabsimulation,thecostofthisessaywasalmostnegligiblewhilewestillgotlargeamountsofdata.Andobservingtheresultsonthecomputeralsosavedalotoftime.It’sobviousthatcomputertechnologyisveryhelpfulfortheelectricalengineering.
VI.Appendix
ScreenshotofMatlabModel:
（PartB）
（PartC:
plusthirdharmonicinjection）
References:
[1]BinWu,“High-powerConvertersandACDrives”
[2]王晶，翁国庆，张有兵.电力系统的MATLAB/SIMULINK仿真与应用[M].西安：
西安电子科技大学出版社，2008
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