Item5InverterCircuit項目五逆變電路Themodeofinvertercircuittransfer5.1逆變電路的換流方式TeachingResourcesDatabaseof

NationalVocationalEducationPowerSupplyTechnologyBilingualcourses.Powerelectronicstechnology電力電子技術Themodeofinvertercircuittransfer5.1逆變電路的換流方式什么是逆變？為什么要逆變？

Whatisinversion?Whyinversion?逆變——把直流電轉變成交流電，是整流的逆過程。Inversion-Turnthedirectcurrentintoalternatingcurrent,isthereverseprocessofrectification.有源逆變電路——交流側和電網連結

Activeinvertercircuit-ACsideisconnectedtothegrid應用：直流可逆調速系統、交流繞線轉子異步電動機串級調速以及高壓直流輸電等Applications:DCreversiblespeedregulationsystem,ACwindingrotorasynchronousmotorcascadespeedregulationandHVDCtransmissionetc..對于可控整流電路，滿足一定條件就可工作于有源逆變，其電路形式未變，只是電路工作條件轉變。既工作在整流狀態又工作在逆變狀態，稱為變流電路Forthecontrollablerectationcircuit,tomeetcertainconditionscanworkintheactiveinverter,itscircuitformhasnotchanged,butthecircuitworkingconditionschange.Itworksbothintherectitionstateandintheinvertedstate,calledconvertorcircuit實例：電力機車下坡行駛，機車的位能轉變為電能，反送到交流電網中去Example:Whenanelectriclocomotiverunsdownhill,thepotentialenergyofthelocomotiveisconvertedintoelectricenergyandsentbacktotheACgrid逆變電路——把直流電逆變成交流電的電路Invertercircuit-acircuitthatconvertsdirectcurrentintoalternatingcurrent無源逆變——變流電路的交流側不與電網聯接，而直接接到負載。Passiveinverter-theACsideoftheconvertercircuitisnotconnectedtothegrid,butdirectlyconnectedtotheload.換流——電流從一個支路向另一個支路轉移的過程，也稱為換相。Conversion--Theprocessbywhichanelectriccurrentistransferredfromonebranchtoanother.Alsocalledcommutation.開通

Openup：適當的門極驅動信號就可使器件開通。Thedevicecanbeopenupbytheappropriategatedrivesignal.關斷Shutoff：全控型器件可通過門極關斷。Thefullycontrolleddevicecanbeturnedoffbythegate.半控型器件晶閘管，必須利用外部條件才能關斷。Thethyristorofthesemi-controlleddevicemustbeturnedoffbyexternalconditions.一般在晶閘管電流過零后施加一定時間反壓，才能關斷。Generallyinthethyristorcurrentafterzerotoapplyacertaintimebackpressure,canbeturnedoff.研究換流方式主要是研究如何使器件關斷。Thestudyofconvertermodeismainlytostudyhowtoturnoffthedevice.Themodeofinvertercircuittransfer5.1逆變電路的換流方式1)器件換流

Devicecommutation利用全控型器件的自關斷能力進行換流。Usetheself-shutdownabilityofthefullycontrolleddeviceforcurrentcommutation.在采用IGBT、電力MOSFET、GTO、GTR等全控型器件的電路中的換流方式是器件換流。InthecircuitusingIGBT,powerMOSFET,GTO,GTRandotherall-controlleddevicesinthecircuitisthedevicetransfer.2)電網換流

Powernetworkcommutation電網提供換流電壓的換流方式。Amethodofcommutationinwhichthegridprovidescommutationvoltage.將負的電網電壓施加在欲關斷的晶閘管上即可使其關斷。不需要器件具有門極可關斷能力，但不適用于沒有交流電網的無源逆變電路。Applyinganegativegridvoltagetothethyslicalgatetubethatyouwanttoshutdown,thenyoucanshutsitdown.Thedeviceisnotrequiredtohavegate-offcapability,butisnotsuitableforpassiveinvertercircuitswithoutanACgrid.3)

負載換流

Loadcommutation4)強迫換流

ForcedcommutationThemodeofinvertercircuittransfer5.1逆變電路的換流方式圖1負載換流電路及其工作波形Fig.1load-commutatedcircuitanditsworkingwaveform?t?t?t?tOOOOiit1b)a)uouoioiouVTiVT1iVT4iVT2iVT3uVT1uVT4負載換流

LoadcommutationThemodeofinvertercircuittransfer5.1逆變電路的換流方式由負載提供換流電壓的換流方式。Commutingmodeinwhichthecommutationvoltageisprovidedbytheload.負載電流的相位超前于負載電壓的場合，都可實現負載換流。Whenthephaseoftheloadcurrentisaheadoftheloadvoltage,theloadcommutationcanberealized.如圖是基本的負載換流電路，4個橋臂均由晶閘管組成。Asshowninthefigure,isthebasicload-commutatedcircuit,thefourbridgearmsarecomposedofthyslgates.整個負載工作在接近并聯諧振狀態而略呈容性。Thewholeloadworksinastateofnearparallelresonanceandslightlycapacitive.直流側串電感，工作過程可認為id

基本沒有脈動。DCsideseriesinductance,theworkingprocesscanbeconsideredthatidbasicallynopulsation.負載對基波的阻抗大而對諧波的阻抗小。所以uo接近正弦波。Theimpedanceoftheloadtothefundamentalwaveislargeandtheimpedancetotheharmonicwaveissmall.Souo

isclosetoasinewave.注意觸發VT2、VT3的時刻t1必須在uo過零前并留有足夠的裕量，才能使換流順利完成。PayattentiontothetriggeringtimeofVT2andVT3.t1mustbebeforeUOcrosseszeroandleaveenoughsparecapacitytomakethecommutationcompletesmoothly.由換流電路內電容直接提供換流電壓直接耦合式強迫換流通過換流電路內的電容和電感的耦合來提供換流電壓或換流電流電感耦合式強迫換流設置附加的換流電路，給欲關斷的晶閘管強迫施加反壓或反電流的換流方式稱為強迫換流。Setupanadditionaltransflowcircuit,forcingthethylocktubetobeshutdowntoapplyareversepressureoranti-currenttransfermodecalledforcedcommutation.通常利用附加電容上所儲存的能量來實現，因此也稱為電容換流。Thisisusuallyachievedbyusingtheenergystoredonanadditionalcapacitor,soitisalsocalledcapacitivecommutation.分類

ClassificationThemodeofinvertercircuittransfer5.1逆變電路的換流方式強迫換流ForcedcommutationThecommutatorvoltageisdirectlysuppliedbythecapacitorintheconvectorcircuitDirectlycoupledforcedcommutationToprovideacommutatorvoltageorcurrentthroughthecouplingofacapacitorandinductorinaconvectorcircuitInductivelycoupledforcedconverter圖2直接耦合式強迫換流原理圖Fig.2Schematicdiagramofdirectlycoupledforcedcommutation圖3電感耦合式強迫換流原理圖Fig.3Schematicdiagramofinductivelycoupledforcedconverter電感耦合式強迫換流

Inductivelycoupledforcedconverter先使晶閘管電流減為零，然后通過反并聯二極管使其加上反向電壓。Thethyristorcurrentisreducedtozero,andthenthereversevoltageisappliedtothethyristorthroughthereverseshuntdiode.也叫電流換流。Alsocalledcurrentconversion.Themodeofinvertercircuittransfer5.1逆變電路的換流方式直接耦合式強迫換流

Directlycoupledforcedcommutation當晶閘管VT處于通態時，預先給電容充電。當S合上，就可使VT被施加反壓而關斷。WhenthethyristorVTisintheopenstate,thecapacitorischargedinadvance.WhenSisclosed,VTcanbeturnedoffbyapplyingbackpressure.也叫電壓換流。Alsocalledvoltagecommutation.LoadLoadLoadThemodeofinvertercircuittransfer5.1逆變電路的換流方式換流方式總結

Summaryofconvertermode：器件換流——適用于全控型器件。Devicecommutation-suitableforfullycontrolleddevices.其余三種方式——針對晶閘管。Theotherthreeways-forthyristors.器件換流和