逆变器外文文献及翻译.docx

逆变器外文文献及翻译.docx

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逆变器外文文献及翻译

Inverter

1Introduction

Aninverterisanelectricaldevicethatconvertsdirectcurrent（DC）toalternatingcurrent（AC）；theconvertedACcanbeatanyrequiredvoltageandfrequencywiththeuseofappropriatetransformers，switching,andcontrolcircuits。

Solid—stateinvertershavenomovingpartsandareusedinawiderangeofapplications，fromsmallswitchingpowersuppliesincomputers，tolargeelectricutilityhigh-voltagedirectcurrentapplicationsthattransportbulkpower.InvertersarecommonlyusedtosupplyACpowerfromDCsourcessuchassolarpanelsorbatteries。

Therearetwomaintypesofinverter.Theoutputofamodifiedsinewaveinverterissimilartoasquarewaveoutputexceptthattheoutputgoestozerovoltsforatimebeforeswitchingpositiveornegative.Itissimpleandlowcostandiscompatiblewithmostelectronicdevices,exceptforsensitiveorspecializedequipment,forexamplecertainlaserprinters.Apuresinewaveinverterproducesanearlyperfectsinewaveoutput（<3％totalharmonicdistortion）thatisessentiallythesameasutility—suppliedgridpower.ThusitiscompatiblewithallACelectronicdevices。

Thisisthetypeusedingrid-tieinverters。

Itsdesignismorecomplex,andcosts5or10timesmoreperunitpowerTheelectricalinverterisahigh—powerelectronicoscillator。

ItissonamedbecauseearlymechanicalACtoDCconvertersweremadetoworkinreverse,andthuswere"inverted"，toconvertDCtoAC.Theinverterperformstheoppositefunctionofarectifier。

2Applications

2.1DCpowersourceutilization

AninverterconvertstheDCelectricityfromsourcessuchasbatteries,solarpanels,orfuelcellstoACelectricity.Theelectricitycanbeatanyrequiredvoltage；inparticularitcanoperateACequipmentdesignedformainsoperation,orrectifiedtoproduceDCatanydesiredvoltageGridtieinverterscanfeedenergybackintothedistributionnetworkbecausetheyproducealternatingcurrentwiththesamewaveshapeandfrequencyassuppliedbythedistributionsystem。

Theycanalsoswitchoffautomaticallyintheeventofablackout。

Micro-invertersconvertdirectcurrentfromindividualsolarpanelsintoalternatingcurrentfortheelectricgrid。

Theyaregridtiedesignsbydefault.

2。

2Uninterruptiblepowersupplies

Anuninterruptiblepowersupply（UPS）usesbatteriesandaninvertertosupplyACpowerwhenmainpowerisnotavailable。

Whenmainpowerisrestored，arectifiersuppliesDCpowertorechargethebatteries。

2.3Inductionheating

InvertersconvertlowfrequencymainACpowertoahigherfrequencyforuseininductionheating.Todothis,ACpowerisfirstrectifiedtoprovideDCpower。

TheinverterthenchangestheDCpowertohighfrequencyACpower.

2.4HVDCpowertransmission

WithHVDCpowertransmission，ACpowerisrectifiedandhighvoltageDCpoweristransmittedtoanotherlocation。

Atthereceivinglocation,aninverterinastaticinverterplantconvertsthepowerbacktoAC.

2.5Variable—frequencydrives

Avariable-frequencydrivecontrolstheoperatingspeedofanACmotorbycontrollingthefrequencyandvoltageofthepowersuppliedtothemotor。

Aninverterprovidesthecontrolledpower.Inmostcases,thevariable-frequencydriveincludesarectifiersothatDCpowerfortheinvertercanbeprovidedfrommainACpower。

Sinceaninverteristhekeycomponent，variable-frequencydrivesaresometimescalledinverterdrivesorjustinverters.

2.6Electricvehicledrives

Adjustablespeedmotorcontrolinvertersarecurrentlyusedtopowerthetractionmotorsinsomeelectricanddiesel-electricrailvehiclesaswellassomebatteryelectricvehiclesandhybridelectrichighwayvehiclessuchastheToyotaPriusandFiskerKarma.Variousimprovementsininvertertechnologyarebeingdevelopedspecificallyforelectricvehicleapplications.［2］Invehicleswithregenerativebraking,theinverteralsotakespowerfromthemotor（nowactingasagenerator）andstoresitinthebatteries。

2。

7Thegeneralcase

AtransformerallowsACpowertobeconvertedtoanydesiredvoltage，butatthesamefrequency。

Inverters，plusrectifiersforDC,canbedesignedtoconvertfromanyvoltage,ACorDC,toanyothervoltage,alsoACorDC,atanydesiredfrequency。

Theoutputpowercanneverexceedtheinputpower,butefficienciescanbehigh,withasmallproportionofthepowerdissipatedaswasteheat.

3Circuitdescription

3.1Basicdesigns

Inonesimpleinvertercircuit,DCpowerisconnectedtoatransformerthroughthecentretapoftheprimarywinding.AswitchisrapidlyswitchedbackandforthtoallowcurrenttoflowbacktotheDCsourcefollowingtwoalternatepathsthroughoneendoftheprimarywindingandthentheother。

Thealternationofthedirectionofcurrentintheprimarywindingofthetransformerproducesalternatingcurrent（AC）inthesecondarycircuit。

Theelectromechanicalversionoftheswitchingdeviceincludestwostationarycontactsandaspringsupportedmovingcontact.Thespringholdsthemovablecontactagainstoneofthestationarycontactsandanelectromagnetpullsthemovablecontacttotheoppositestationarycontact.Thecurrentintheelectromagnetisinterruptedbytheactionoftheswitchsothattheswitchcontinuallyswitchesrapidlybackandforth。

Thistypeofelectromechanicalinverterswitch,calledavibratororbuzzer,wasonceusedinvacuumtubeautomobileradios。

Asimilarmechanismhasbeenusedindoorbells,buzzersandtattooguns。

Astheybecameavailablewithadequatepowerratings，transistorsandvariousothertypesofsemiconductorswitcheshavebeenincorporatedintoinvertercircuitdesigns

3。

2Outputwaveforms

Theswitchinthesimpleinverterdescribedabove,whennotcoupledtoanoutputtransformer,producesasquarevoltagewaveformduetoitssimpleoffandonnatureasopposedtothesinusoidalwaveformthatistheusualwaveformofanACpowersupply。

UsingFourieranalysis，periodicwaveformsarerepresentedasthesumofaninfiniteseriesofsinewaves.Thesinewavethathasthesamefrequencyastheoriginalwaveformiscalledthefundamentalcomponent.Theothersinewaves，calledharmonics,thatareincludedintheserieshavefrequenciesthatareintegralmultiplesofthefundamentalfrequency.

Thequalityofoutputwaveformthatisneededfromaninverterdependsonthecharacteristicsoftheconnectedload.Someloadsneedanearlyperfectsinewavevoltagesupplyinordertoworkproperly。

Otherloadsmayworkquitewellwithasquarewavevoltage.

3.3Threephaseinverters

Three—phaseinvertersareusedforvariable-frequencydriveapplicationsandforhighpowerapplicationssuchasHVDCpowertransmission.Abasicthree-phaseinverterconsistsofthreesingle-phaseinverterswitcheseachconnectedtooneofthethreeloadterminals。

Forthemostbasiccontrolscheme，theoperationofthethreeswitchesiscoordinatedsothatoneswitchoperatesateach60degreepointofthefundamentaloutputwaveform.Thiscreatesaline—to—lineoutputwaveformthathassixsteps。

Thesix-stepwaveformhasazero-voltagestepbetweenthepositiveandnegativesectionsofthesquare—wavesuchthattheharmonicsthataremultiplesofthreeareeliminatedasdescribedabove.Whencarrier—basedPWMtechniquesareappliedtosix-stepwaveforms，thebasicoverallshape,orenvelope,ofthewaveformisretainedsothatthe3rdharmonicanditsmultiplesarecancelled

4History

4.1Earlyinverters

Fromthelatenineteenthcenturythroughthemiddleofthetwentiethcentury，DC-to—ACpowerconversionwasaccomplishedusingrotaryconvertersormotor—generatorsets（M-Gsets）.Intheearlytwentiethcentury,vacuumtubesandgasfilledtubesbegantobeusedasswitchesininvertercircuits.Themostwidelyusedtypeoftubewasthethyratron。

Theoriginsofelectromechanicalinvertersexplainthesourceoftheterminverter。

EarlyAC-to—DCconvertersusedaninductionorsynchronousACmotordirect—connectedtoagenerator（dynamo）sothatthegenerator'scommutatorreverseditsconnectionsatexactlytherightmomentstoproduceDC。

Alaterdevelopmentisthesynchronousconverter，inwhichthemotorandgeneratorwindingsarecombinedintoonearmature，withslipringsatoneendandacommutatorattheotherandonlyonefieldframe。

TheresultwitheitherisAC—in,DC-out。

WithanM—Gset,theDCcanbeconsideredtobeseparatelygeneratedfromtheAC；withasynchronousconverter,inacertainsenseitcanbeconsideredtobe”mechanicallyrectifiedAC”.Giventherightauxiliaryandcontrolequipment,anM-Gsetorrotaryconvertercanbe"runbackwards"，convertingDCtoAC.Henceaninverterisaninvertedconverter.

4.2Controlledrectifierinverters

Sinceearlytransistorswerenotavailablewithsufficientvoltageandcurrentratingsformostinverterapplications，itwasthe1957introductionofthethyristororsilicon-controlledrectifier（SCR）thatinitiatedthetransitiontosolidstateinvertercircuits。

ThecommutationrequirementsofSCRsareakeyconsiderationinSCRcircuitdesigns。

SCRsdonotturnofforcommutateautomaticallywhenthegatecontrolsignalisshutoff。

Theyonlyturnoffwhentheforwardcurrentisreducedtobelowtheminimumholdingcurrent，whichvarieswitheachkindofSCR，throughsomeexternalprocess。

ForSCRsconnectedtoanACpowersource,commutationoccursnaturallyeverytimethepolarityofthesourcevoltagereverses。

SCRsconnectedtoaDCpowersourceusuallyrequireameansofforcedcommutationthatforcesthecurrenttozerowhencommutationisrequired.TheleastcomplicatedSCRcircuitsemploynaturalcommutationratherthanforcedcommutation.Withtheadditionofforcedcommutationcircuits，SCRshavebeenusedinthetypesofinvertercircuitsde