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1、IEEETRANSACTIONSONINDUSTRYAPPLICATIONS.VOL.IA-23,NO.5,SEPTEMBER/OCTOBER1987887NewPWMMethodforFullyDigitizedInvertersYOSHIHIROMURAI,ASSOCIATEMEMBER,IEEE,KAZUHARUOHASHI,ANDISAMUHOSONOAbstract-ThedevelopmentofdigitaldeviceshasledtotheproductionofPWMinvertersfordrivinginductionmotorshavinghigh-freque
2、ncycarriersover10000Hz.However,thepopulardigitaldevicesexhibitdifficultiesinarrivingatthepreciseswitchinginstantsbecauseoflimitationofavailablememorycapacityandofbits,especiallyinthelow-frequencyregion.Basicdiscussionsonthemagneticfluxandtorquerippleandanintroductiontoamemory-savingandlow-torque-
3、ripplenewPWM(splitzerovector)methodaregiven.Theexperimentsshowfairlygoodcurrentwaveforms,lowironloss,andlowacousticnoise.I.INTRODUCTIONFig.1.PWMinverterforinductionmotordrive.THEdevelopmentofdigitaldevicesenabledthelpulsewidth-modulated(PWM)invertersfordrivinginductionmotorstohaveavery-high-frequ
4、encycarrierofmorethan10000Hz[1].Motorperformances,suchastorqueripple,copperloss,andacousticnoise,areimprovedtosomeextent.Thedigitalcircuit,however,hasthelimitationinavailablefrequencyofdigitalbitnumbersfortheexpressionofthePWMpatternandeachdurationtime.Forexample,inthepopularinvertersysteminFig.1
5、,ifthewell-knownsubhar-monicPWM,orsine-wavePWM,[2],[3](showninFig.2)isusedtodrivethetransistors,thePWMoutputpotentialisdesignedbycomparingthesignalsinewavewiththecarrierLttrianglewave.Toexpressdigitallythetriangleandthe%IVasinusoid,thecircuitutilizesthedigitalbitsforthetwowaves.nHowever,inthelow-
6、frequencyrange,forexample,iftheH[u11InMPnnnnnn2Tamplituderatio(A,/As)oftrianglewaveandthesinusoidalwaveisselectedtobe20,thedigitalaccuracyofthesinusoidtobe8bits=256,andthecarrierfrequencytobe10kHz,theFig.2.Subharmonicmethodandphaseapotential.clockfrequencyneededwillbe20x256x2x10kHz=102.4MHz.Thisi
7、saverysevereconditionfornormalswitchingdevices.Iftheclockisselectedtobelow,theoutputII.FLUXLINKAGEANDPWMPATTERNsignalwavemustbeexpressedby3-5bits,andthePWMA.CircularLocusPWMoutputwavebecomesdistorted.ThePWMpatternandth
