Electric machine control for energy efficient electric drive systems

131 Pages·2015·10.84 MB·English

THESISFORTHEDEGREEOFLICENTIATEOFENGINEERING
Electric machine control for energy efficient electric drive
systems
ANDREASANDERSSON
DepartmentofEnergyandEnvironment
DivisionofElectricPowerEngineering
CHALMERSUNIVERSITYOFTECHNOLOGY
Göteborg,Sweden2015
Electricmachinecontrolforenergyefficientelectricdrivesystems
ANDREASANDERSSON
©ANDREASANDERSSON,2015.
LicentianteThesisattheGraduateSchoolinEnergyandEnvironment
DepartmentofEnergyandEnvironment
DivisionofElectricPowerEngineering
ChalmersUniversityofTechnology
SE–41296Göteborg
Sweden
Telephone[phone]
ChalmersBibliotek,Reproservice
Göteborg,Sweden2015
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Electricmachinecontrolforenergyefficiencyelectricdrivesystems
ANDREASANDERSSON
DepartmentofEnergyandEnvironment
ChalmersUniversityofTechnology
Abstract
Pure electric vehicles and hybrid electric vehicles are of increasing interest in
theautomotiveindustry,muchduetochallengessuchasemissionlevellegislationsand
the environmentalimpact of the transportation sector. When continuously striving for
better performing and more energy efficient electric powertrains, with high drivability
andredundancy,thereisaneverincreasingneedforfurtherresearchanddevelopmentin
theareasofcontrols,designandsystemleveloptimization.
Over the past decade, noise and vibrationsfrom electric driveshas increasingly
becomean area of attentionfor both academiaand industry. The absence of the broad
bandnoisefromtheinternalcombustionenginebringsnewnoise, vibrationandharsh-
ness (NVH) challengesforelectric propulsionapplications. Magneticnoise fromelec-
tricalmachinesisofparticularinterestinautomotiveapplications. Itisnotonlyrelated
to the physicaldesignand mountingof the electricalmachinebutalso to the choiceof
controlapproachandvoltagemodulationstrategy.
This thesis is focused on energy efficiency enhancements in the electric drive
system,primarilyonthecontrolofthethreephaseinverter.Inadditiontotheenergyeffi-
ciencyperspective,alsotheappearanceofelectromagneticforcesandNVH-perspectives
areconsidered. Alternativemodulationtechniquesareinvestigated,wherethesocalled
discontinuouspulse width modulationis is provento decrease the inverter losses, sub-
stantially.
Theappearanceofelectromagneticforcesisinvestigatedextensively,withfocus
onradialforcesactingasattractiveorrepulsiveforcesbetweentherotorandthestator.Its
influenceonstatordeformations,andconsequentlynoiseandvibrations,isinvestigated
wherealsoinfluenceofmachinedesign,modulationtechniquesandperceivedannoyance
oftheradiatedsoundareincluded.
The scientific contribution can be summarized with two parts. Firstly, the in-
terdisciplinary research where energy efficiency enhancements are coupled to NVH-
performance. Secondly, the cause and effect of electromagnetic forces as the link be-
tweenmachinedesign,controlsandNVH-perspectives.
ItisproventhatwhenusingdiscontinuousPWM(DPWM)insteadofsynchronous
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PWM(SPWM),theinverterlossescanbedecreasedwithupto-17percent.Whilecom-
plementingthemodulationwithrandomizationoftheswitchingfrequencytheincreasein
perceivedannoyance,duetoincreasedradiatednoisewhenusingDPWM,issignificantly
decreased. Atrotationalspeedsabovebasespeed,nodifferenceinperceivedannoyance
betweenDPWMandSPWMcouldstatisticallybeensuredwhenrandomizationisused.
Ata randomizationlevelwithavarianceofs =1000Hzthe noiseiscomparablewith
the magnitude of the harmonics themselves, hence further randomization in terms of
increasedvarianceiswithoutanygain.
IndexTerms: Energyefficiency,modulationtechniques,noiseassessment,permanent
magnetsynchronousmachine(PMSM).
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Acknowledgements
First and foremost I would like to thank Professor Torbjörn Thiringer, my aca-
demic supervisor and examiner, for his continuous and consistent support during the
work. I wouldalso liketo thankDr. StefanLundberg,myacademicco-supervisor,for
his time and contributions,especially with the extensivesupportwith the experimental
work.AspecialthanksgoestoDr.JonnLantzatVolvoCarGroup,myindustrialsupervi-
sor,forhistimeandsupportaswellastheindustrialcontributions.Theworkisfounded
byVolvoCarGroupandtheSwedishEnergyAgency,botharegratefullyacknowledged
forthefinancialsupport.
Manypeople,bothatVolvoCarsandatChalmers,havebeeninvolvedtovarying
degreesandby theirsupport,knowledgeandhelpfulnessinfluencedthe work. I would
liketothankthemall,especiallymycolleaguesattheDivisionofElectricPowerEngi-
neeringatChalmersandtheDepartmentofElectricPropulsionSystemsatVolvoCars.
AndreasAndersson
Göteborg,Sweden
Autumn,2015
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Contents
Abstract v
Acknowledgements vii
Contents ix
1 Introduction 1
1.1 Problembackground . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Purposeofthethesisandcontributions . . . . . . . . . . . . . . . . . . 2
1.3 Thesisoutline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4 Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Electricdrivesystem 5
2.1 Salient-polePMSMmodelling . . . . . . . . . . . . . . . . . . . . . . 6
2.1.1 Equivalentcircuitmodel . . . . . . . . . . . . . . . . . . . . . 6
2.1.2 PMSMcontrol . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.3 Maximumtorqueperamperewithvariableinductances . . . . . 8
2.2 Three-phasevoltagesourceinverter . . . . . . . . . . . . . . . . . . . 10
2.3 Pulsewidthmodulationtechniques . . . . . . . . . . . . . . . . . . . . 12
2.3.1 SPWMwiththirdharmonicinjection . . . . . . . . . . . . . . 14
2.3.2 DiscontinuousPWM . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.3 RandomPWM . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.4 Losscalculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.4.1 Corelosscalculations . . . . . . . . . . . . . . . . . . . . . . 19
2.4.2 Inverterlosses. . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.5 Longitudinalvehicledynamicsmodelling . . . . . . . . . . . . . . . . 21
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Contents
3 ElectromagneticforcesinrelationtoNVHforaPMSM 23
3.1 Modalanalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.2 Airgapfluxdensity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.2.1 Appearanceoffluxdensity . . . . . . . . . . . . . . . . . . . . 26
3.2.2 Effectsofstatorslots . . . . . . . . . . . . . . . . . . . . . . . 31
3.3 Electromagneticforces . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.4 Radialandtangentialcomponents . . . . . . . . . . . . . . . . . . . . 35
3.5 Statordynamicresponseandradiatedsoundpower . . . . . . . . . . . 38
4 Experimentalsetup 43
4.1 Testingequipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.1.1 Inverterandelectricalmachine . . . . . . . . . . . . . . . . . . 44
4.1.2 Noisemeasurements . . . . . . . . . . . . . . . . . . . . . . . 46
4.1.3 Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.2 Testprocedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
5 Finiteelementmodelling 51
5.1 2DANSYSMaxwellmodel . . . . . . . . . . . . . . . . . . . . . . . 52
5.1.1 Machineparameteridentification . . . . . . . . . . . . . . . . 52
5.1.2 Harmonicsininducedvoltage . . . . . . . . . . . . . . . . . . 53
5.2 SensitivityofMaxwell2D-model. . . . . . . . . . . . . . . . . . . . . 55
5.2.1 Sensitivityanalysisofmeshsize . . . . . . . . . . . . . . . . . 56
5.2.2 Sensitivityanalysisoftimestepsize . . . . . . . . . . . . . . . 58
5.3 VoltageexcitedFEmodellinginANSYSMaxwell . . . . . . . . . . . 60
5.3.1 Derivationofinducedvoltage . . . . . . . . . . . . . . . . . . 61
5.3.2 Statorwindingresistancehandling . . . . . . . . . . . . . . . . 62
5.3.3 Initialphasecurrent. . . . . . . . . . . . . . . . . . . . . . . . 62
5.3.4 ProposedsimulationsequenceinANSYSMaxwell . . . . . . . 63
5.4 ANSYSmulti-physicssimulations . . . . . . . . . . . . . . . . . . . . 67
5.4.1 Simulationsetup . . . . . . . . . . . . . . . . . . . . . . . . . 67
6 Theoreticalanalysisofelectromagneticfluxandforcedensity 69
6.1 Influenceofstatorslots . . . . . . . . . . . . . . . . . . . . . . . . . . 70
6.1.1 Closedstator . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
6.1.2 Variationofstatorslotopeningwidth . . . . . . . . . . . . . . 72
6.2 Inverterswitchinginfluenceonforcedensityharmonics . . . . . . . . . 77
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