電氣工程及其自動化專業(yè)英語 課件 Chapter 5 High Voltage Direct Current Transmission (HVDC)

目錄Introduction5.1ConvertersinHVDC5.2ApplicationofHVDC5.3HVDCinChina5.4Chapter5HighVoltageDirect

CurrentTransmission(HVDC)HVDCn.高壓直流輸電solid-statePowerDevicen.固態(tài)功率設(shè)備converter[k?n'v?:t?]n.變流器anode['?n?ud]n.陽極cathode['k?θ?ud]n.陰極forwardcurrent正向?qū)娏鱠iode['dai?ud]n.二極管P-Njunctionn.PN結(jié)silicon-controlledrectifiern.晶閘管leakagecurrent漏電流emitter

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onedirection.MOSFETdiodebilateralswitchdiodecapacitanceABCD提交單選題1分collector[k?'lekt?]n.集電極rectifier'rektifai?]n.整流器full-waven.全波harmonic[hɑ:'m?nik]n.諧波vacuumtubediode真空二極管seleniumrectifiersi'li:ni?m]

n.硒整流器Half-waven.半波transformer[tr?ns'f?:m?,tr?nz-,trɑ:n-]

n.變壓器center-tappedadj.中間抽頭的solarpanel太陽能板sinewave正弦波Themainfunctionof()circuitsistoconvertACtoDC.rectifierinverterchoppercircuitelectricgeneratorABCD提交單選題1分gridtieinverter并網(wǎng)逆變器electricgrid電網(wǎng)uninterruptiblepowersupply(UPS)不間斷電源inverter[in'v?:t?]n.逆變器electromechanical[i,lektr?umi'k?nik?l]

adj.機電的totalharmonicdistortion(THD)n.總諧波畸變率squarewaven.方波H-bridgeinvertern.H橋逆變器resonant['rez?n?nt]

adj.諧振的antiparalleldiode[,?nti'p?r?lel]

n.反并聯(lián)二極管freewheelingdiode['fri:'wi:li?]n.續(xù)流二極管LinearintegralcomparemethodwasproposedtorealizePWM(),whichcanincreasethewavefrequency.triangularwavesawtoothwavesinewavesquarewaveABCD提交單選題1分pulse-widthmodulation(PWM)脈寬調(diào)制semiconductor[,semik?n'd?kt?,,semai-]n.半導(dǎo)體alternator['?:lt?neit?]

n.交流發(fā)電機root-mean-square均方根ripple['ripl]

n.紋波impedance[im'pi:d?ns]

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n.熒光燈照明Maximumpowerpointtracking最大功率點跟蹤Micro-invertern.微型逆變器staticinverterplant靜態(tài)逆變站variable-frequencydrive變頻驅(qū)動Thesolarcell:That’scompletelynotintricate.It’ssimplyafewlayersof（）.semiconductornonconductorsuperconductorresistorABCD提交單選題1分vibrator[vai'breit?]n.振蕩器buzzer['b?z?]

n.蜂鳴器sinusoidal[,sin?'s?idl]

adj.正弦的directcurrent直流alternatingcurrent交流underwaterpowercable海底電力電纜mercuryarc['m?:kjuri]

汞弧integratedgate-commutatedthyristor集成門極換流晶閘管MOScontrolledthyristorsMOS可控晶閘管gateturn-offthyristor門極可關(guān)斷晶閘管insulated-gatebipolartransistor絕緣柵雙極型晶體管Theprocessofreconstructingafunctionoftimeorspacefromits()componentsdeterminedinFourieranalysis.tangentialcotangentsinusoidalsecantABCD提交單選題1分目錄Introduction5.1ConvertersinHVDC5.2ApplicationofHVDC5.3HVDCinChina5.45.1IntroductionThetransmissionsystemisbecomingevenmorecomplex.Highvoltage(ineitherACorDCelectricalpowertransmissionapplications)isusedforelectricpowertransmissiontoreducetheenergylostintheresistanceofthewires.Foragivenquantityofpowertransmittedandsizeofconductor,doublingthevoltagewilldeliverthesamepoweratonlyhalfthecurrent.傳輸系統(tǒng)正在變得更加復(fù)雜。高壓(無論在交流還是直流電力傳輸應(yīng)用中)用于電力傳輸，以減少電線電阻中的能量損失。對于給定的傳輸功率和導(dǎo)體尺寸，將電壓增加一倍將以一半的電流提供相同的功率。5.1IntroductionSincethepowerlostasheatinthewiresisproportionaltothesquareofthecurrent,butdoesnotdependinanymajorwayonthevoltagedeliveredbythepowerline,doublingthevoltageinapowersystemreducestheline-loss,lossperunitofelectricalpowerdeliveredbyafactorof4.Powerlossintransmissionlinescanalsobereducedbyreducingresistance,forexample,byincreasingthediameteroftheconductor,butlargerconductorsareheavierandmoreexpensive.由于在電線中以熱的形式損失的功率與電流的平方成正比，而與導(dǎo)線沿線的電壓沒有任何關(guān)系。因此如果將電力系統(tǒng)中的電壓變?yōu)樵瓉淼膬杀犊梢韵鄳?yīng)的使線路中的損耗減少為原來的1/4。輸電線路中的功率損耗也可以通過減小電阻來降低，例如，增加導(dǎo)體的直徑，但是尺寸大的導(dǎo)體會更重，更昂貴。5.1IntroductionHighvoltagescannoteasilybeusedforlightingandmotors,andsotransmission-levelvoltagesmustbereducedtovaluescompatiblewithend-useequipment.Transformersareusedtochangethevoltagelevelinalternatingcurrent(AC)transmissioncircuits.Thecompetitionbetweenthedirectcurrent(DC)ofThomasEdisonandtheACofNikolaTeslaandGeorgeWestinghousewasknownastheWarofCurrents.高電壓不容易用于照明和電機，因此傳輸?shù)燃壍碾妷罕仨毥档偷浇K端設(shè)備能接受的電壓值。變壓器是用來改變交流輸電電路中的電壓等級的。托馬斯·愛迪生的直流電與尼古拉·特斯拉和喬治·威斯汀豪斯的交流電之間的競爭被稱為“電流之戰(zhàn)”。5.1IntroductionTheadvantageofHVDCistheabilitytotransmitlargeamountsofpoweroverlongdistanceswithlowercapitalcostsandwithlowerlossesthanAC.Dependingonvoltagelevelandconstructiondetails,lossesarequotedasabout3%per1,000km.High-voltagedirectcurrenttransmissionallowsefficientuseofenergysources,remotefromloadcenters.高壓直流輸電的優(yōu)勢在于能夠以較低的投資成本和比交流更低的損耗遠距離傳輸大量電力。根據(jù)電壓水平和施工細節(jié)，損耗約為每1000公里3%。高壓直流輸電可以有效地利用能源，遠離負荷中心。5.1IntroductionInanumberofapplicationsHVDCismoreeffectivethanACtransmission.Examplesinclude:Underseacables,wherehighcapacitancecausesadditionalAClosses.(e.g.,250kmBalticCablebetweenSwedenandGermany,the600kmNorNedcablebetweenNorwayandtheNetherlands,and290kmBasslinkbetweentheAustralianmainlandandTasmania)在許多應(yīng)用中，高壓直流輸電比交流輸電更有效。例如:海底電纜，其中高壓電容引起額外的交流損耗。(例如，瑞典和德國之間250公里的波羅的海電纜，挪威和荷蘭之間600公里的NorNed電纜，以及澳大利亞大陸和塔斯馬尼亞之間290公里的Basslink電纜)5.1IntroductionEndpoint-to-endpointlong-haulbulkpowertransmissionwithoutintermediate'taps',forexample,inremoteareasIncreasingthecapacityofanexistingpowergridinsituationswhereadditionalwiresaredifficultorexpensivetoinstallPowertransmissionandstabilizationbetweenunsynchronisedACdistributionsystems比如在偏遠地區(qū)，不需要中間節(jié)點的“點對點”長距離大容量電力傳輸；增加現(xiàn)有電網(wǎng)的容量但是在很難再安裝額外線路或安裝費用太貴的情況；（解決）兩非同步交流配電系統(tǒng)間的電力傳輸與穩(wěn)定的問題5.1IntroductionConnectingaremotegeneratingplanttothedistributiongrid,forexampleNelsonRiverBipoleStabilizingapredominantlyACpower-grid,withoutincreasingprospectiveshortcircuitcurrent將發(fā)電廠與遙遠的配電網(wǎng)連接，例如納爾遜河的雙極輸電線路不增加預(yù)期的短路電流，以保證主干交流電網(wǎng)的穩(wěn)定性。5.1IntroductionReducinglinecost.HVDCneedsfewerconductorsasthereisnoneedtosupportmultiplephases.Also,thinnerconductorscanbeusedsinceHVDCdoesnotsufferfromtheskineffectFacilitatepowertransmissionbetweendifferentcountriesthatuseACatdifferingvoltagesand/orfrequenciesSynchronizeACproducedbyrenewableenergysources降低線路成本。因為不需要支持多個相，高壓直流輸電需要導(dǎo)線數(shù)量少。此外，由于HVDC不受集膚效應(yīng)的影響，可以使用更細的導(dǎo)線有利于不同交流的電壓和/或頻率的地區(qū)之間的電力傳輸可再生能源發(fā)電同步并網(wǎng)5.1IntroductionLongundersea/undergroundhighvoltagecableshaveahighelectricalcapacitance,sincetheconductorsaresurroundedbyarelativelythinlayerofinsulationandametalsheathwhiletheextensivelengthofthecablemultipliestheareabetweentheconductors.深海/地下高壓電纜具有高電容，因為導(dǎo)體被相對較薄的絕緣層和金屬護套包圍，而電纜的長長度使導(dǎo)體之間的面積成倍增加。5.1IntroductionThegeometryisthatofalongco-axialcapacitor.Wherealternatingcurrentisusedforcabletransmission,thiscapacitanceappearsinparallelwithload.Additionalcurrentmustflowinthecabletochargethecablecapacitance,whichgeneratesadditionallossesintheconductorsofthecable.Additionally,thereisadielectriclosscomponentinthematerialofthecableinsulation,whichconsumespower.幾何形狀是一個長同軸電容器。當(dāng)交流電用于電纜傳輸時，該電容與負載并行出現(xiàn)。額外的電流必須在電纜中流動以給電纜電容充電，這會在電纜的導(dǎo)體中產(chǎn)生額外的損耗。此外，在電纜絕緣材料中存在介質(zhì)損耗成分，它會消耗功率。5.1IntroductionHowever,whendirectcurrentisused,thecablecapacitanceischargedonlywhenthecableisfirstenergizedorwhenthevoltageischanged;thereisnosteady-stateadditionalcurrentrequired.ForalongACunderseacable,theentirecurrent-carryingcapacityoftheconductorcouldbeusedtosupplythechargingcurrentalone.然而，當(dāng)使用直流時，電纜電容只有在電纜首次通電或電壓改變時才會充電;不需要額外的穩(wěn)態(tài)電流。對于長交流海底電纜，導(dǎo)體的全部載流容量有可能全被用于提供充電電流（而損耗殆盡）。5.1IntroductionThecablecapacitanceissuelimitsthelengthandpowercarryingcapacityofACcables.DCcableshavenosuchlimitation,andareessentiallyboundbyonlyOhm'sLaw.AlthoughsomeDCleakagecurrentcontinuestoflowthroughthedielectricinsulators,thisisverysmallcomparedtothecableratingandmuchlessthanACtransmissioncables.電纜電容問題會影響交流電纜的長度和承載能力。直流電纜沒有這樣的限制，本質(zhì)上只受歐姆定律的約束。雖然一些直流泄漏電流繼續(xù)流過介質(zhì)絕緣體，但與電纜額定功率相比，這是非常小的，比交流傳輸電纜要小得多。5.1IntroductionHVDCcancarrymorepowerperconductorbecause,foragivenpowerrating,theconstantvoltageinaDClineisthesameasthepeakvoltageinanACline.ThepowerdeliveredinanACsystemisdefinedbytherootmeansquare(RMS)ofanACvoltage,butRMSisonlyabout71%ofthepeakvoltage.ThepeakvoltageofACdeterminestheactualinsulationthicknessandconductorspacing.高壓直流輸電每根導(dǎo)體可以承載更多的功率，因為在給定的額定功率下，直流線路的恒定電壓與交流線路的峰值電壓相同。交流系統(tǒng)中輸出的功率由交流電壓的均方根(RMS)定義，但RMS僅為峰值電壓的71%左右。交流電的峰值電壓決定了實際的絕緣厚度和導(dǎo)體間距。5.1IntroductionBecauseDCoperatesataconstantmaximumvoltage,thisallowsexistingtransmissionlinecorridorswithequallysizedconductorsandinsulationtocarrymorepowerintoanareaofhighpowerconsumptionthanAC,whichcanlowercosts.由于直流電在恒定的最大電壓下運行，這使得具有相同尺寸導(dǎo)體和絕緣的現(xiàn)有輸電線路走廊能夠比交流輸電線路在高功耗區(qū)域輸送更多的電力，從而降低成本。5.1IntroductionBecauseHVDCallowspowertransmissionbetweenunsynchronizedACdistributionsystems,itcanhelpincreasesystemstability,bypreventingcascadingfailuresfrompropagatingfromonepartofawiderpowertransmissiongridtoanother.ChangesinloadthatwouldcauseportionsofanACnetworktobecomeunsynchronizedandseparatewouldnotsimilarlyaffectaDClink,andthepowerflowthroughtheDClinkwouldtendtostabilizetheACnetwork.由于HVDC允許電力在不同步的交流配電系統(tǒng)之間傳輸，它可以通過防止級聯(lián)故障從更廣泛的輸電網(wǎng)絡(luò)的一部分傳播到另一部分來幫助提高系統(tǒng)的穩(wěn)定性。負載的變化導(dǎo)致交流電網(wǎng)的某些部分變得不同步和解列這樣的問題不會同樣影響直流網(wǎng)，并且通過直流網(wǎng)的功率流更有利于交流電網(wǎng)的穩(wěn)定。5.1IntroductionThemagnitudeanddirectionofpowerflowthroughaDClinkcanbedirectlycommanded,andchangedasneededtosupporttheACnetworksateitherendoftheDClink.ThishascausedmanypowersystemoperatorstocontemplatewideruseofHVDCtechnologyforitsstabilitybenefitsalone.通過直流鏈路的功率流的大小和方向可以直接命令，并根據(jù)需要改變，以支持直流鏈路兩端的交流網(wǎng)絡(luò)。這使得許多電力系統(tǒng)運營商考慮更廣泛地使用高壓直流技術(shù)，因為它具有穩(wěn)定的好處。5.1IntroductionHVDCislessreliableandhasloweravailabilitythanACsystems,mainlyduetotheextraconversionequipment.Singlepolesystemshaveavailabilityofabout98.5%,withaboutathirdofthedowntimeunscheduledduetofaults.Faultredundantbipolesystemsprovidehighavailabilityfor50%ofthelinkcapacity,butavailabilityofthefullcapacityisabout97%to98%.與交流系統(tǒng)相比，HVDC的可靠性和可用性較低，主要是由于額外的轉(zhuǎn)換設(shè)備。單極系統(tǒng)的可用性約為98.5%，其中約三分之一的停機時間是由于故障造成的。故障冗余雙極系統(tǒng)提供50%鏈路容量的高可用性，但全容量的可用性約為97%~98%。5.1IntroductionTherequiredstaticinvertersareexpensiveandhavelimitedoverloadcapacity.AtsmallertransmissiondistancesthelossesinthestaticinvertersmaybebiggerthaninanACtransmissionline.Thecostoftheinvertersmaynotbeoffsetbyreductionsinlineconstructioncostandlowerlineloss.所需的靜態(tài)逆變器價格昂貴，過載能力有限。在較小的傳輸距離下，靜態(tài)逆變器中的損耗可能比交流傳輸線中的損耗大。逆變器的成本可能不會被線路建設(shè)成本的降低和線路損耗的降低所抵消。5.1IntroductionWithtwoexceptions,allformermercuryrectifiersworldwidehavebeendismantledorreplacedbythyristorunits.Pole1oftheHVDCschemebetweentheNorthandSouthIslandsofNewZealandstillusesmercuryarcrectifiers,asdoesPole1oftheVancouverIslandlinkinCanada.Botharecurrentlybeingreplaced–inNewZealandbyanewthyristorpoleandinCanadabyathree-phaseAClink.除了兩個例外，世界上所有以前的汞整流器都已被拆除或被晶閘管裝置所取代。新西蘭南北島之間的高壓直流輸電方案的第1極仍然使用汞弧整流器，加拿大溫哥華島連接的第1極也是如此。目前，這兩種線路都在被替換——在新西蘭用一個新的晶閘管極，在加拿大用一個三相交流線路。5.1IntroductionEfficientdesignsuseSilicon-ControlledRectifiers(SCR)s(themorecommonnameforthyristors)firedinsequenceat60HztoproduceamodifiedsinewaveofACcurrent,similartotheinvertercircuitryinmodernbattery-operatedUPSsforcomputerandtelecomuse.高效的設(shè)計使用硅控整流器(SCR)s(晶閘管更常見的名稱)在60赫茲的順序發(fā)射，以產(chǎn)生交流電流的修改正弦波，類似于用于計算機和電信使用的現(xiàn)代電池供電的ups中的逆變電路。5.1IntroductionIncontrasttoACsystems,realizingmultiterminalsystemsiscomplex,asisexpandingexistingschemestomultiterminalsystems.ControllingpowerflowinamultiterminalDCsystemrequiresgoodcommunicationbetweenalltheterminals;powerflowmustbeactivelyregulatedbytheinvertercontrolsysteminsteadoftheinherentimpedanceandphaseanglepropertiesofthetransmissionline.與交流系統(tǒng)相比，實現(xiàn)多終端系統(tǒng)是復(fù)雜的，將現(xiàn)有方案擴展到多終端系統(tǒng)也是復(fù)雜的。在多端子直流系統(tǒng)中，控制潮流需要各端子之間良好的通信;功率流必須由逆變器控制系統(tǒng)主動調(diào)節(jié)，而不是由傳輸線固有的阻抗和相角特性來調(diào)節(jié)。5.1IntroductionMulti-terminallinesarerare.OneisinoperationattheHydroQuébec–NewEnglandtransmissionfromRadissontoSandyPond.AnotherexampleistheSardinia-mainlandItalylinkwhichwasmodifiedin1989alsoprovidepowertotheislandofCorsica.多終端線路很少見。其中一個正在從雷迪森(Radisson)到桑迪塘(SandyPond)的魁北克水電公司-新英格蘭輸電系統(tǒng)中運行。另一個例子是1989年修改的撒丁島-意大利大陸連接，也為科西嘉島提供電力。5.1IntroductionHighvoltageDCcircuitbreakersaredifficulttobuildbecausesomemechanismmustbeincludedinthecircuitbreakertoforcecurrenttozero,otherwisearcingandcontactwearwouldbetoogreattoallowreliableswitching.高壓直流斷路器很難制造，因為必須在斷路器中包含一些機制來強制電流為零，否則電弧和接觸磨損會太大，無法實現(xiàn)可靠的開關(guān)。5.1IntroductionOperatingaHVDCschemerequiresmanysparepartstobekept,oftenexclusivelyforonesystemasHVDCsystemsarelessstandardizedthanACsystemsandtechnologychangesfaster.NormallymanufacturerssuchasAlstom,SiemensandABBdonotstatespecificcostinformationofaparticularprojectsincethisisacommercialmatterbetweenthemanufacturerandtheclient.運行高壓直流方案需要保留許多備件，通常只用于一個系統(tǒng)，因為高壓直流系統(tǒng)比交流系統(tǒng)標準化程度低，而且技術(shù)變化更快。通常制造商，如阿爾斯通，西門子和ABB不說明特定項目的具體成本信息，因為這是制造商和客戶之間的商業(yè)問題。5.1IntroductionCostsvarywidelydependingonthespecificsoftheprojectsuchaspowerrating,circuitlength,overheadvs.underwaterroute,landcosts,andACnetworkimprovementsrequiredateitherterminal.AdetailedevaluationofDCvs.ACcostmayberequiredwherethereisnocleartechnicaladvantagetoDCaloneandonlyeconomicsdrivestheselection.成本取決于項目的具體情況，如額定功率、電路長度、架空線路與水下線路、土地成本以及兩端所需的交流網(wǎng)絡(luò)改進。如果單獨使用直流沒有明顯的技術(shù)優(yōu)勢，只有經(jīng)濟因素驅(qū)動選擇，則可能需要對直流與交流成本進行詳細評估。5.1IntroductionHoweversomepractitionershavegivenoutsomeinformationthatcanbereasonablywellreliedupon:Foran8GW40kmlinklaidundertheEnglishChannel,thefollowingareapproximateprimaryequipmentcostsfora2000MW500kVbipolarconventionalHVDClink(excludeway-leaving,on-shorereinforcementworks,consenting,engineering,insurance,etc.)然而，一些從業(yè)人員提供了一些相當(dāng)可靠的信息:對于鋪設(shè)在英吉利海峽下的一條8吉瓦40公里的線路，以下是一條2000兆瓦500千伏雙極性傳統(tǒng)高壓直流線路的大致主要設(shè)備成本(不包括開路、岸上加固工程、許可、工程、保險等)。5.1IntroductionConverterstations~￡110MSubseacable+installation~￡1M/kmSoforan8GWcapacitybetweenEnglandandFranceinfourlinks,littleisleftoverfrom￡750Mfortheinstalledworks.Addanother￡200–300Mfortheotherworksdependingonadditionalonshoreworksrequired.換流站~1.1億英鎊海底電纜+安裝成本~100萬英鎊/公里因此，對于英法之間4條線路的8GW容量，7.5億英鎊的安裝工程幾乎沒有剩余。還根據(jù)需要的額外陸上工程，另外增加2-3億英鎊用于其他工程。5.1IntroductionAnApril,2010announcementfora2,000MWline,64km,betweenSpainandFrance,is700millioneuros,thisincludesthecostofatunnelthroughthePyrenees.2010年4月，在西班牙和法國之間修建一條總長64公里、容量為2000兆瓦的輸電線路，耗資7億歐元，其中包括一條穿越比利牛斯山脈的隧道。目錄Introduction5.1ConvertersinHVDC5.2ApplicationofHVDC5.3HVDCinChina5.45.2ConvertersinHVDC

5.2.1Solid-statePowerDeviceinHVDC

Powerelectronicscanbedefinedastheconversionandconditioningofelectricpowerusingelectronicswitches.Thefivemajortypesofpowersemiconductorsusedinsolid-stateACmotorcontrolare:(1)Diodes(2)Thyristors[e.g.,silicon-controlledrectifier(SCR)](3)Transistors(4)Gate-turn-offthyristors電力電子學(xué)可以定義為利用電子開關(guān)對電力進行轉(zhuǎn)換和調(diào)節(jié)。固態(tài)交流電機控制中使用的五種主要功率半導(dǎo)體是:(1)二極管(2)晶閘管[如可控硅整流器]

(3)晶體管(4)閘管關(guān)斷晶閘管5.2.1Solid-statePowerDeviceinHVDCThecommonalityofthesedevicesistheuseofcrystalsofsiliconintheformofwafersthatarelayeredsoastoformvariouscombinationsofP-Njunction.ThePjunctionisusuallycalledtheanodeandNjunctionisusuallycalledthecathodefordiodes,SCRs,andGTOs;thecorrespondingtermsfortransistomarecollectorandemitter.Thedifferencesamongthesedevicesrelatetohowtheygointoandoutofconductionandintheiravailableampereandvoltagecapabilities.這些器件的共同點是使用硅晶體的晶圓形式，這些晶圓是分層的，從而形成各種組合的pn結(jié)。對于二極管、可控硅和gto,P結(jié)通常稱為陽極，N結(jié)通常稱為陰極;晶體管對應(yīng)的術(shù)語是集電極和發(fā)射極。這些器件之間的差異與它們?nèi)绾芜M入和退出傳導(dǎo)以及它們可用的安培和電壓能力有關(guān)。5.2.1Solid-statePowerDeviceinHVDCMostoftheHVDCsystemsinoperationtodayarebasedonLine-CommutatedConverters.Earlystaticsystemsusedmercuryarcrectifiers,whichwereunreliable.TwoHVDCsystemsusingmercuryarcrectifiersarestillinservice.目前運行的大多數(shù)高壓直流系統(tǒng)都是基于線路換向轉(zhuǎn)換器。早期的靜態(tài)系統(tǒng)使用的是不可靠的汞弧整流器。兩個使用汞弧整流器的高壓直流輸電系統(tǒng)仍在使用中。5.2.1Solid-statePowerDeviceinHVDCMostoftheHVDCsystemsinoperationtodayarebasedonLine-CommutatedConverters.Earlystaticsystemsusedmercuryarcrectifiers,whichwereunreliable.TwoHVDCsystemsusingmercuryarcrectifiersarestillinservice.目前運行的大多數(shù)高壓直流系統(tǒng)都是基于線路換向轉(zhuǎn)換器。早期的靜態(tài)系統(tǒng)使用的是不可靠的汞弧整流器。兩個使用汞弧整流器的高壓直流輸電系統(tǒng)仍在使用中。5.2.1Solid-statePowerDeviceinHVDCTheinsulated-gatebipolartransistor(IGBT)isnowalsoused,formingaVoltageSourcedConverter,andofferssimplercontrol,reducedharmonicsandreducedvalvecost.BecausethevoltagesinHVDCsystems,upto800kVinsomecases,exceedthebreakdownvoltagesofthesemiconductordevices,HVDCconvertersarebuiltusinglargenumbersofsemiconductorsinseries.現(xiàn)在也使用絕緣柵雙極晶體管(IGBT)，形成電壓源轉(zhuǎn)換器，并提供更簡單的控制，減少諧波和降低閥成本。由于高壓直流系統(tǒng)中的電壓在某些情況下高達800千伏，超過了半導(dǎo)體器件的擊穿電壓，因此高壓直流變流器采用大量串聯(lián)的半導(dǎo)體。5.2.1Solid-statePowerDeviceinHVDCThelow-voltagecontrolcircuitsusedtoswitchthethyristorsonandoffneedtobeisolatedfromthehighvoltagespresentonthetransmissionlines.Thisisusuallydoneoptically.Inahybridcontrolsystem,thelow-voltagecontrolelectronicssendslightpulsesalongopticalfibrestothehigh-sidecontrolelectronics.用于開關(guān)晶閘管的低壓控制電路需要與傳輸線上的高壓隔離。這通常是光學(xué)的。在混合控制系統(tǒng)中，低壓控制電子器件沿著光纖向高壓控制電子器件發(fā)送光脈沖。5.2.1Solid-statePowerDeviceinHVDCThelow-voltagecontrolcircuitsusedtoswitchthethyristorsonandoffneedtobeisolatedfromthehighvoltagespresentonthetransmissionlines.Thisisusuallydoneoptically.Inahybridcontrolsystem,thelow-voltagecontrolelectronicssendslightpulsesalongopticalfibrestothehigh-sidecontrolelectronics.用于開關(guān)晶閘管的低壓控制電路需要與傳輸線上的高壓隔離。這通常是光學(xué)的。在混合控制系統(tǒng)中，低壓控制電子器件沿著光纖向高壓控制電子器件發(fā)送光脈沖。5.2.1Solid-statePowerDeviceinHVDCAnothersystem,calleddirectlighttriggering,dispenseswiththehigh-sideelectronics,insteadusinglightpulsesfromthecontrolelectronicstoswitchlight-triggeredthyristors(LTTs).Acompleteswitchingelementiscommonlyreferredtoasavalve,irrespectiveofitsconstruction.另一種系統(tǒng)，稱為直接光觸發(fā)，省去了高端的電子設(shè)備，而是使用來自控制電子設(shè)備的光脈沖來開關(guān)光觸發(fā)晶閘管(ltt)。不管其結(jié)構(gòu)如何，一個完整的開關(guān)元件通常被稱為閥門。5.2.2RectifyingsystemsinHVDCSystemsRectificationandinversionuseessentiallythesamemachinery.Manysubstations(ConverterStations)aresetupinsuchawaythattheycanactasbothrectifiersandinverters.AttheACend,asetoftransformers,oftenthreephysicallyseparatedsingle-phasetransformers,isolatethestationfromtheACsupply,toprovidealocalearth,andtoensurethecorrecteventualDCvoltage.整流和反轉(zhuǎn)基本上使用相同的機械。許多變電站(換流站)都是以這樣一種方式設(shè)置的，即它們既可以充當(dāng)整流器又可以充當(dāng)逆變器。在交流端，一組變壓器，通常是三個物理隔離的單相變壓器，將該站與交流電源隔離開來，提供局部接地，并確保正確的最終直流電壓。5.2.2RectifyingsystemsinHVDCSystemsTheoutputofthesetransformersisthenconnectedtoabridgerectifierformedbyanumberofvalves.Thebasicconfigurationusessixvalves,connectingeachofthethreephasestoeachofthetwoDCrails.However,withaphasechangeonlyeverysixtydegrees,considerableharmonicsremainontheDCrails.然后將這些變壓器的輸出連接到由若干閥組成的橋式整流器上。基本配置使用六個閥，將三相中的每一個連接到兩個直流軌道。然而，只有一個相位變化每60度，相當(dāng)大的諧波留在直流軌道上。5.2.2RectifyingsystemsinHVDCSystemsAnenhancementofthisconfigurationuses12valves(oftenknownasatwelve-pulsesystem).TheACissplitintotwoseparatethreephasesuppliesbeforetransformation.Oneofthesetsofsuppliesisthenconfiguredtohaveastar(wye)secondary,theotheradeltasecondary,establishingathirtydegreephasedifferencebetweenthetwosetsofthreephases.這種配置的改進使用了12個閥(通常稱為12脈沖系統(tǒng))。在改造前，交流電被分成兩個獨立的三相電源。其中一組電源配置為星形次級電源，另一組配置為三角形次級電源，在兩組三相之間建立30度的相位差。5.2.2RectifyingsystemsinHVDCSystemsWithtwelvevalvesconnectingeachofthetwosetsofthreephasestothetwoDCrails,thereisaphasechangeevery30degrees,andharmonicsareconsiderablyreduced.通過12個閥將兩組三相中的每一組連接到兩個直流軌道，每30度發(fā)生一次相位變化，諧波大大減少。5.2.2RectifyingsystemsinHVDCSystemsInadditiontotheconversiontransformersandvalve-sets,variouspassiveresistiveandreactivecomponentshelpfilterharmonicsoutoftheDCrails.RectifiercircuitsareoftenclassifiedbythenumberofcurrentpulsesthatflowtotheDCsideoftherectifierpercycleofACinputvoltage.除了轉(zhuǎn)換變壓器和閥組外，各種無源電阻和無功元件有助于過濾直流軌道中的諧波。整流電路通常根據(jù)每個交流輸入電壓周期流入整流器直流側(cè)的電流脈沖數(shù)來分類。5.2.2RectifyingsystemsinHVDCSystemsAsingle-phasehalf-waverectifierisaone-pulsecircuitandasingle-phasefull-waverectifierisatwo-pulsecircuit.Athree-phasehalf-waverectifierisathree-pulsecircuitandathree-phasefull-waverectifierisasix-pulsecircuit.單相半波整流器是一個單脈沖電路，單相全波整流器是一個雙脈沖電路。三相半波整流器是一個三脈沖電路，三相全波整流器是一個六脈沖電路。5.2.2RectifyingsystemsinHVDCSystemsWiththree-phaserectifiers,twoormorerectifiersaresometimesconnectedinseriesorparalleltoobtainhighervoltageorcurrentratings.Therectifierinputsaresuppliedfromspecialtransformersthatprovidephaseshiftedoutputs.Thishastheeffectofphasemultiplication.Sixphasesareobtainedfromtwotransformers,twelvephasesfromthreetransformersandsoon.Theassociatedrectifiercircuitsare12-pulserectifiers,18-pulserectifiersandsoon.對于三相整流器，兩個或多個整流器有時串聯(lián)或并聯(lián)，以獲得更高的電壓或電流額定值。整流器輸入由提供相移輸出的特殊變壓器提供。這就產(chǎn)生了相位倍增的效果。從兩個變壓器得到6相，從三個變壓器得到12相，以此類推。配套的整流電路有12脈沖整流、18脈沖整流等。5.2.2RectifyingsystemsinHVDCSystemsWhencontrolledrectifiercircuitsareoperatedintheinversionmode,theywouldbeclassifiedbypulsenumberalso.RectifiercircuitsthathaveahigherpulsenumberhavereducedharmoniccontentintheACinputcurrentandreducedrippleintheDCoutputvoltage.Intheinversionmode,circuitsthathaveahigherpulsenumberhavelowerharmoniccontentintheACoutputvoltagewaveform.當(dāng)受控的整流器電路工作在逆變狀態(tài)時，也可按脈沖數(shù)進行分類。具有較高脈沖數(shù)的整流電路減少了交流輸入電流中的諧波含量，降低了直流輸出電壓中的紋波。在逆變方式中，脈沖數(shù)較高的電路在交流輸出電壓波形中的諧波含量較低。5.2.2RectifyingsystemsinHVDCSystemsA.RectifierdevicesBeforethedevelopmentofsiliconsemiconductorrectifiers,vacuumtubediodesandcopperoxideorseleniumrectifierstackswereused.Highpowerrectifiers,suchasareusedinhigh-voltagedirectcurrentpowertransmission,nowuniformlyemploysiliconsemiconductordevicesofvarioustypes.A.整流設(shè)備在硅半導(dǎo)體整流器發(fā)展之前，使用的是真空管二極管和過氧化物銅或硒整流器堆。大功率整流器，如用于高壓直流電力傳輸，現(xiàn)在統(tǒng)一采用各種類型的硅半導(dǎo)體器件。5.2.2RectifyingsystemsinHVDCSystemsThesearethyristorsorothercontrolledswitchingsolid-stateswitcheswhicheffectivelyfunctionasdiodestopasscurrentinonlyonedirection.B.Half-waverectificationInhalfwaverectification,eitherthepositiveornegativehalfoftheACwaveispassed,whiletheotherhalfisblocked.這些是晶閘管或其他受控開關(guān)固態(tài)開關(guān)，它們有效地起二極管的作用，只在一個方向上通過電流。B.半波整流在半波整流中，交流波的正或負一半通過，而另一半被阻擋。5.2.2RectifyingsystemsinHVDCSystemsBecauseonlyonehalfoftheinputwaveformreachestheoutput,itisveryinefficientifusingpowertransfer.Half-waverectificationcanbeachievedwithasinglediodeinaone-phasesupply,orwiththreediodesinathree-phasesupply.由于只有一半的輸入波形到達輸出，如果使用功率傳輸，效率非常低。半波整流可以在單相電源中用一個二極管實現(xiàn)，也可以在三相電源中用三個二極管實現(xiàn)。圖5.1使用2個二極管的半波整流器5.2.2RectifyingsystemsinHVDCSystemsTheoutputDCvoltageofahalfwaverectifiercanbecalculatedwiththefollowingtwoidealequations:半波整流器的輸出直流電壓可以用以下兩個理想方程來計算:5.2.2RectifyingsystemsinHVDCSystemsC.Full-waverectificationAfull-waverectifierconvertsthewholeoftheinputwaveformtooneofconstantpolarity(positiveornegative)atitsoutput.Full-waverectificationconvertsbothpolaritiesoftheinputwaveformtoDC(directcurrent),andismoreefficient.C.全波整流全波整流器在其輸出端將整個輸入波形轉(zhuǎn)換為具有恒定極性(正或負)的波形。全波整流將輸入波形的兩個極性轉(zhuǎn)換為直流(直流電)，效率更高。5.2.2RectifyingsystemsinHVDCSystemsHowever,inacircuitwithanon-centertappedtransformer,fourdiodesarerequiredinsteadoftheoneneededforhalf-waverectification.(Seesemiconductors,diode).Fourdiodesarrangedthiswayarecalledadiodebridgeorbridgerectifier.然而，在非中心抽頭變壓器的電路中，需要四個二極管而不是半波整流所需的一個二極管。(參見半導(dǎo)體，二極管)。這樣排列的四個二極管稱為二極管橋或橋式整流器。5.2.2RectifyingsystemsinHVDCSystemsForsingle-phaseAC,ifthetransformeriscenter-tapped,thentwodiodesback-to-back(i.e.anodes-to-anodeorcathode-to-cathode)canformafull-waverectifier.Twiceasmanywindingsarerequiredonthetransformersecondarytoobtainthesameoutputvoltagecomparedtothebridgerectifierabove.圖5.2格萊茨橋式整流器:采用4個二極管的全波整流器對于單相交流如果變壓器是中心抽頭，那么兩個背靠背二極管(即陽極對陽極或陰極對陰極)可以形成一個全波整流器。與橋式整流器相比，二級變壓器需要兩倍的繞組才能獲得相同的輸出電壓。5.2.2RectifyingsystemsinHVDCSystems圖5.3采用中心抽頭變壓器和2個二極管的全波整流器Averycommonvacuumtuberectifierconfigurationcontainedonecathodeandtwinanodesinsideasingleenvelope;inthisway,thetwodiodesrequiredonlyonevacuumtube.一個非常常見的真空管整流器配置包含一個陰極和雙陽極，這樣，兩個二極管只需要一個真空管。5.2.2RectifyingsystemsinHVDCSystemsForthree-phaseAC,sixdiodesareused.Typicallytherearethreepairsofdiodes,eachpair,though,isnotthesamekindofdoublediodethatwouldbeusedforafullwavesingle-phaserectifier.Insteadthepairsareinseries(anodetocathode).Typically,commerciallyavailabledoublediodeshavefourterminalssotheusercanconfigurethemassingle-phasesplitsupplyuse,forhalfabridge,orforthree-phaseuse.對于三相交流，使用六個二極管。通常有三對二極管，但每對都不是用于全波單相整流器的雙二極管。相反，這些對是串聯(lián)的(陽極到陰極)。通常，市售雙二極管有四個端子，因此用戶可以將其配置為單相分路供電使用，半橋或三相使用。5.2.2RectifyingsystemsinHVDCSystemsMostdevicesthatgeneratealternatingcurrent(suchdevicesarecalledalternators)generatethree-phaseAC.Forexample,anautomobilealternatorhassixdiodesinsideittofunctionasafull-waverectifierforbatterychargingapplications.大多數(shù)產(chǎn)生交流電的設(shè)備(這種設(shè)備稱為交流發(fā)電機)產(chǎn)生三相交流電。例如，汽車交流發(fā)電機內(nèi)部有六個二極管，作為電池充電應(yīng)用的全波整流器。5.2.2RectifyingsystemsinHVDCSystems圖5.4三相交流輸入，半波整流和全波整流直流輸出波形5.2.2RectifyingsystemsinHVDCSystemsFig.5.4showedtheinput3-phasesignalsand6-pulseoutputwaveformofhalf&fullwaverectifier.Theaverageandroot-mean-squareoutputvoltagesofanidealsingle