IEEE-Effective EMI filter design method for three

EffectiveEMIFilterDesignMethodforThree-PhaseInverterbaseduponSoftwareNoiseSeparationPo-ShenChenandYen-ShinLaiCenterforPowerElectronicsTechnology1,Sec.3,Chung-HsiaoE.Rd.,Taipei,10608,Taipei,TaiwanAbstract—Thispaperpresentsanewdesignmethodofthree-phaseinverterformotordrivesusingsoftwarenoiseseparationmethod.Therefore,nohardwarenoiseseparatorisrequired.Moreover,thepresentedEMIfilterdesignapproachprovidessystematicdesignprocedureandthereforetrial-and-erroroverheadisnotrequiredandtherebyshorteningthedevelopmenttimeandsavingthecost.Thepresentedmethoddeterminescommon-modechokeanddifferential-modechokebasedupontherequiredimpedanceoftoattenuatethenoise.Athree-phaseinverterforinductormotordrivesisusedastheEUTandtherelatedconductiveEMIfilterisdesignedandverified.ItwillbeshownthatEMIfilterdesignedbythissystematicdesignmethodeffectivelyattenuatestheEMIcomponentstomeettherequirementofEN55011.Keywords-Common-modeanddifferential-modesignals,EMIfilter,three-phaseinverterൕ.ProblemDescriptionandObjectivesInvertershavebeenwidelyappliedtomotordrives,renewableenergyconversionandothers.Althoughgivingthespecifiedvoltageandfrequencyofinverteristhemainconcernsforinvertercontrol,electromagneticinterference(EMI)issuemainlycontributedbyPWMswitchingbecomesmorepopular,especiallyforresidentialapplications.TodealwiththeEMIissuesofthree-phaseinverter,severalmethodshavebeendiscussed.Forthree-phaseinverterswithcapacitors,common-modefilterscanbeusedtoreducethecommon-modeEMIcomponentsasreportedin[1-2].Noiseseparationmethodsforthree-phaseinverterEMIsignalshavebeendiscussedin[3-7].In[8-9],EMIfilterisinstalledbetweeninputpowerandinverterbaseduponcornerfrequencymethod[8-9]orButterworthfiltermethod[10].Fortheseapproaches,systematicdesignprocedureofEMIfilterdesignhasnotbeendiscussedorhighfrequencynoisecan’tbeeffectivelysuppressed[9].Fig.1showstheattenuationandcornerfrequencyforpreviousfilterdesignmethod.AsshowninFig.1,thecornerfrequencyoffilterisdeterminedbydrawingthe40dB/decadeslopelinewhichistangenttotherequiredcommon-modeordifferential-modecomponents.However,thehighfrequencycomponentsmaynoteffectivelysuppresstheEMInoiseasillustratedinFig.2.ForFig.2,thehighfrequencynoise,indicatedby“HF”inFig.2,theEMInoisecan’tbereducedeffectivelybythefilterwithslopeof(-40)dB/decade.Moreover,theEMInoisecan’tbemitigatedtomeettherequiredstandardduetothefrequencydependencyofthecharacteristicfeaturesforfiltercomponents.Duetothechangeofcomponentsoffilter,noiseattenuationcontributedfilterischangedfromthatfor“idealfilter”to“realfilter”asshowninFig.3.Fig.1.Attenuationandcornerfrequencyforfilterdesign,previousmethod.Fig.2.IllustrationoffailurecaseforEMInoisesuppression,previousfilterdesignmethod.Fig.3.FailurecaseforEMInoisesuppression,frequencydependentcharacteristicsoffiltercomponents.914The2010InternationalPowerElectronicsConference978-1-4244-5393-1/10/$26.00©2010IEEEThemainthemeofthispaperistopresentasystematicapproachtotheconductiveEMIfilterdesignforthethree-phaseinverterbaseduponsoftwarenoiseseparationmethod[11-12].Baseduponthepresentedsystematicmethod,thetoleranceofnoisefromtherequiredstandardcanbespecifiedandtheEMIfilterisdesignedaccordingly.Therefore,trial-and-error,whichmaynotbeallowedforhighpowerinverter,isnotrequiredforthepresentedfilterdesignmethod.Moreover,thecharacteristicsoffiltercomponentsareinvestigatedinthispapertoguaranteeeffectivenoisesuppression.Aninductionmotordriveusingthree-phaseinverteristheEUTforexperimentalverification.Theinductionmotorisoperatedintheratedspeedandload,andtheinverterswitchingfrequencyisupto15kHz.ItwillbeshownthatEMIfilterdesignedbythissystematicdesignmethodeffectivelyattenuatestheEMIcomponentstomeettherequirementofEN55011[13].ൖ.Software-basedNoiseSeparationMethod(A).Common-modeanddifferential-modenoiseFig.4showstheconductiveEMIsignalsandmeasurementcircuitathree-phasesystem.TheconductiveEMIsignalsareclassifiedascommon-mode(CM)noiseanddifferential-mode(DM)noise,whichcanbeseparatedwitheachotherbyhardwarenoiseseparator[14].RLISNSTTSRLLLCCCGEuqipmentUnderTestUtilityPowerΩ=50LISNRCMCMCMDMToSpectrumTerminalFig.4.ConductiveEMIsignalsandmeasurement.AsshowninFig.1,thecommon-modenoiseisdefinedby:3TSRCMVVVV++=(1)Andtherelateddifferential-modenoisebetweentwophases,sayphase“R”andphase“S”,is:SRRSDMVVV−=−(2)(B).Software-basednoiseseparationmethodFig.5showstheconnectionofthepresentedsoftware-basedseparationmethod.TheCM-noiseandDM-noiseseparationisperformedusingsoftwarewritteninLabVIEWasshowninFig.5.Itisworthyofnotingthatthemeasuredvaluesof“VR”,“VS”and“VT”areindBμVingeneral.Togettheaccuracyresultsusing(1)and(2),itisrequiredtoconvertthevaluesinμVbeforecalculationofVCMandVDM.AfteroperationVCMandVDMareconvertedintermsofdBμV.TheidentificationoverstandardlimitamplitudeoffrequencyforVCMandVDMisveryimportanttothefilterdesign.NNB-4/200XLISNInverter3hpUnshieldMotorCable2mInductionMotor5hpUtilityPower2mR3132SpectrumAnalyzerGPIBNoteBookLabVIEW6.1UnshieldCableFig.5.Set-upofthepresentedsoftware-basedseparationmethod.ൗ.ExperimentalSystemandNoiseSeparation(A).Exper