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1、1、外文原文（復(fù)印件）A:TheUtilityInterfacewithPowerElectronicSystemIntroductionWediscussedvariouspowerlinedisturbancesandhowpowerelectronicconverterscanperformaspowerconditionersanduninterruptiblepowersuppliestopreventthesepowelinedisturbancesfromdisruptingtheoperationofcriticalloadssuchasco
2、mputersusedforcontrollingimportantprocesses,medicalequipment,andthelike.However,allpowerelectronicconverters(includingthoseusedtoprotectcriticalloads)canaddtotheinherentpowerlinedisturbancesbydistortingtheutilitywaveformduetoharmoniccurrentsinjectedintotheutilitygridandbyproducinge
3、lectromagneticinterference,Toillustratetheproblemsduetocurrentharmonicsihintheinputcurrentisofapowerelectronicload,considerthesimpleblockdiagramofFig.1-6A-1.Duetothefinite(non-zero)internalimpedanceoftheutilitysourcewhichissimplyrepresentedbyLsinFig.l-6A-1,thevoltagewaveformatthepo
4、intofcommoncouplingtotheotherloadswillbecomedistorted,whichmaycausethemtomalfunction.Inadditiontothevoltagewaveformdistortion,someotherproblemsduetotheharmoniccurrentsareasfollows:additionalheatingandpossiblyovervoltages(duetoresonanceconditions)intheutility'sdistributionandtransmi
5、ssionequipment,errorsinmeteringandmalfunctionofutilityrelays,interferencewithcommunicationandcontrolsignals,andsoon.Inadditiontotheseproblems,phase-controlledconverterscausenotchesintheutilityvoltagewaveformandmanydrawpowerataverylowdisplacementpowerfactorwhichresultsinaverypoorpow
6、erfactorofoperation.Theforegoingdiscussionshowsthattheproliferationofpowerelectronicsystemsandloadshasthepotentialforsignificantnegativeimpactontheutilitiesthemselves,aswellasontheircustomers.Oneapproachtominimizethisimpactistofiltertheharmoniccurrentsandtheelectromagneticinterfere
7、nce(EMI)producedbythepowerelectronicloads.Abetteralternative,inspiteofasmallincreaseintheinitialcost,maybetodesignthepowerelectronicequipmentsuchthattheharmoniccurrentsandtheEMIarepreventedorminimizedfrombeinggeneratedinthefirstplace.Both,theconcernsabouttheutilityinterfaceandthede
8、signofpowerelectronicequip
