交交变频电路 ACAC frequency conversion circuit中英版

6.2ACtoACfrequencyconversioncircuit6.2交交变频电路Item6AlternatingCurrentconversioncircuit项目六交流变换电路TeachingResourcesDatabaseof

NationalVocationalEducationPowerSupplyTechnologyBilingualcourses.Powerelectronicstechnology电力电子技术交流变换电路：把交流电能的参数（幅值、频率、相位）加以转换的电路。ACconversioncircuit:Acircuitthatconvertstheparameters(amplitude,frequency,phase)ofACenergy.交流电力控制电路ACpowercontrolcircuit

交一交变频电路（直接变频电路）ACtoACfrequencyconversioncircuit(directfrequencyconversioncircuit)维持频率不变改变输出电压的幅值。Changetheamplitudeoftheoutputvoltagewhilekeepingthefrequencyconstant.

将电网频率的交流电直接变换成较低频率的交流电直接变频的同时也可实现电压变换。Thevoltageconversioncanberealizedbydirectlyconvertingthealternatingcurrentofthenetworkfrequencyintothealternatingcurrentofthelowerfrequency.分类Classification6.2ACtoACfrequencyconversioncircuit交交变频电路

交－交变频电路是不通过中间直流环节而把电网频率的交流电直接变换成不同频率（低于交流电源频率）交流电的变流电路。AC-ACfrequencyconversioncircuitisnotthroughtheintermediateDClinkandthenetworkfrequencyofACdirectlyintodifferentfrequency(lowerthantheACpowersupplyfrequency)ACconvertercircuit.

主要用于大功率交流电动机调速系统。ItismainlyusedforhighpowerACmotorspeedregulationsystem.

1）定义Definition2）应用Application图6.4.2单相交流输入时交－交变频电路的波形图Figure6.4.2Waveformdiagramofac-acfrequencyconversioncircuitwithsingle-phaseacinput6.2ACtoACfrequencyconversioncircuit交交变频电路PositivegroupworksNegativegroupblocks1.电路结构和工作原理Circuitstructureandworkingprinciple

◆1）电路结构Circuitstructure

由具有相同特征的两组晶闸管整流电路（正组整流器和反组整流器）反并联构成；Itiscomposedoftwogroupsofthyristorrectifiercircuits(positivegrouprectifierandnegativegrouprectifier)whichhavethesamecharacteristicsinreverseparallel.图6.4.1单相输出交－交变频电路Fig.6.4.1Single-phaseoutputAC-ACfrequencycircuit

◆2）工作原理Workingprinciple

图6.4.2单相交流输入时交－交变频电路的波形图Fig.6.4.2Waveformdiagramofac-acfrequencycircuitwithsingle-phaseacinput

正组整流器工作，反组整流器被封锁，负载端输出电压为上正下负；Thepositivegrouprectifierworks,thenegativegrouprectifierisblocked,andtheoutputvoltageoftheloadendispositiveandnegative.

负组整流器工作，正组整流器被封锁，负载端得到输出电压上负下正；Thenegativegrouprectifierworks,thepositivegrouprectifierisblocked,andtheoutputvoltageattheloadendispositiveandnegative.

以低于电源的频率切换正反组整流器的工作状态,在负载端就可获得交变的输出电压；（如图6.4.2）Byswitchingtheworkingstateofthepositiveandnegativerectifieratafrequencylowerthanthepowersupply,thealternatingoutputvoltagecanbeobtainedattheloadend.(Figure6.4.2)晶闸管的开通与关断必须采用无环流控制方式，防止两组晶闸管桥同时导通；TheopeningandturningoffofthyristormustbecontrolledbynocirculationtopreventthesimultaneousconductionoftwothyristorBridges.6.2ACtoACfrequencyconversioncircuit交交变频电路PositivegroupworksNegativegroupblocksPositivegroupworksNegativegroupblocksPositivegrouprectifierNegativegrouprectifierAcinputAcinput3）电路控制特点Circuitcontrolcharacteristics

（1）一个周期内控制角a固定不变时，输出电压为含有大量的谐波矩形波,(如图6.4.2)对电机的工作很不利WhenthecontrolAngleAisfixedwithinacycle,theoutputvoltageisarectangularwavecontainingalargenumberofharmonics,which(asshowninFig.6.4.2)isveryunfavorabletothemotor图6.4.2单相交流输入时交－交变频电路的波形图Fig.6.4.2Waveformdiagramofac-acfrequencyconversioncircuitwithsingle-phaseacinput

图6.4.3交－交变频电路的波形图（a变化）Fig.6.4.3waveformdiagramofAC-ACfrequencyconversioncircuit(variationofA)

（2）为了让输出电压波形接近正弦波，可按正弦规律对a进行调制。Inordertomaketheoutputvoltagewaveformclosetosinewave,acanbemodulatedaccordingtosinusoidallaw.

正组工作的半个周期内让控制角a按正弦规律从90°逐渐减小到0°，然后逐渐增加到90°。正组整流电流的输出电压的平均值就按正弦规律变化，从零增大到最大,然后从最大减小到零。Duringthehalfcycleofthepositivegroup,letthecontrolAngleAdecreasegraduallyfrom90°to0°andthengraduallyincreaseto90°accordingtothesinelaw.Theaveragevalueoftheoutputvoltageofthepositivegrouprectifiercurrentchangessinusoidally,increasingfromzerotomaximum,andthendecreasingfrommaximumtozero.反组工作的半个周期内采用上述同样的控制方法，就可以得到接近正弦波的输出电压。如图6.4.3Theoutputvoltageclosetosinewavecanbeobtainedbyusingthesamecontrolmethodmentionedaboveinhalfacycleofreversegroupoperation.Asshowninfigure6.4.36.2ACtoACfrequencyconversioncircuit交交变频电路1.电路结构和工作原理Circuitstructureandworkingprinciple

PositivegroupworksNegativegroupblocksPositivegroupworksNegativegroupblocksoutputvoltageAverageoutputvoltage2.变频电路的工作过程（电感性负载）Workingprocessoffrequencyconversioncircuit(inductiveload)

对于电感性负载，输出电压超前电流。Forinductiveloads,theoutputvoltageleadsthecurrent.

一个周期可以分为六个阶段Acyclecanbedividedintosixstages

第一阶段：输出电压过零，u0为正，i0<0，反组整流器工作在有源逆变状态，正组整流器被封锁；Thefirststage:theoutputvoltagecrosseszero,u0ispositivei0<0,thereversegrouprectifierworksintheactiveinverterstate,andthepositivegrouprectifierisblocked;图5.4.1单相输出交－交变频电路Fig.5.4.1single-phaseoutputAC-ACfrequencyconversioncircuit

图5.4.4交-交变频电路电感性负载时的输出电压和电流波形Fig.5.4.4OutputvoltageandcurrentwaveformsofanAC-ACfrequencyconversioncircuitunderinductiveload

6.2ACtoACfrequencyconversioncircuit交交变频电路ACinputACinputNegativegrouprectifierPositivegrouprectifier

第二阶段：电流过零。为无环流死区。Thesecondstage:currentcrossingzeroisnocirculationdeadzone.

第三阶段：i0>0，u0>0。正组整流器工作在整流状态，反组整流器被封锁。Thethirdstage:i0>0，u0>0.Thepositivegrouprectifierworksinthestateofrectification,andthenegativegrouprectifierisblocked.6.2ACtoACfrequencyconversioncircuit交交变频电路2.变频电路的工作过程（电感性负载）Workingprocessoffrequencyconversioncircuit(inductiveload)图6.4.4交-交变频电路电感性负载时的输出电压和电流波形Fig.6.4.4OutputvoltageandcurrentwaveformsofanAC-ACfrequencyconversioncircuitunderinductiveload

图6.4.1单相输出交－交变频电路Fig.6.4.1single-phaseoutputAC-ACfrequencyconversioncircuit

PositivegrouprectifierNegativegrouprectifierACinputACinput

第四阶段：i0>0，u0<0。正组整流器工作有源逆变状态，反组整流器仍被封锁；Stage4:i0>0，u0<0.Thepositivegrouprectifierworksintheactiveinvertingstate,andthenegativegrouprectifierisstillblocked.

第五阶段：电流为零，为无环流死区；Stage5:thecurrentiszeroandthereisnocirculationdeadzone;

第六阶段：i0<0,u0<0，反组整流器工作在整流状态，正组整流器被封锁；Stage6:i0<0,u0<0，thereversegrouprectifierworksinthestateofrectification,andthepositivegrouprectifierisblocked;6.2ACtoACfrequencyconversioncircuit交交变频电路2.变频电路的工作过程（电感性负载）Workingprocessoffrequencyconversioncircuit(inductiveload)图6.4.4交-交变频电路电感性负载时的输出电压和电流波形Fig.6.4.4OutputvoltageandcurrentwaveformsofanAC-ACfrequencyconversioncircuitunderinductiveload

图6.4.1单相输出交－交变频电路Fig.6.4.1single-phaseoutputAC-ACfrequencyconversioncircuit

ACinputACinputPositivegrouprectifierNegativegrouprectifier

小结：Summary

1、哪组整流器电路工作是由输出电流决定，而与输出电压极性无关；Whichsetofrectifiercircuitworkisdeterminedbytheoutputcurrent,andhasnothingtodowiththepolarityoftheoutputvoltage;2、变流电路是工作在整流状态还是逆变状态，则是由输出电压方向和输出电流方向的异同决定；Whethertheconvertercircuitworksinrectificationstateorinverterstateisdeterminedbythesimilaritiesanddifferencesbetweenthedirectionofoutputvoltageandthedirectionofoutputcurrent.

6.2ACtoACfrequencyconversioncircuit交交变频电路2.变频电路的工作过程（电感性负载）Workingprocessoffrequencyconversioncircuit(inductiveload)图6.4.4交-交变频电路电感性负载时的输出电压和电流波形Fig.6.4.4OutputvoltageandcurrentwaveformsofanAC-ACfrequencyconversioncircuitunderinductiveload

图6.4.1单相输出交－交变频电路Fig.6.4.1single-phaseoutputAC-ACfrequencyconversioncircuit

PositivegrouprectifierNegativegrouprectifierACinputACinput三相输出交－交变频电路ThreephaseoutputAC-ACfrequencyconversioncircuit

由三组输出电压相位各相差1200的单相交－交变频电路组成。Itiscomposedofthreegroupsofsingle-phaseAC-ACinvertercircuitswithoutputvoltageandphasedifferenceof1200.

电路接线形式主要有两种：Therearetwomainformsofcircuitwiring:

1）公共交流母线进线方式Publiccommunicationbusentrymode

2）输出星形联结方式Outputstarconnectionmode

交－交变频器主要用于交流调速系统中，实际使用的主要是三相交－交变频器。AC-ACfrequencyconverterismainlyusedinACspeedcontrolsystem,theactualuseismainlythree-intersection-ACfrequencyconverter.

6.2ACtoACfrequencyconversioncircuit交交变频电路1.公共交流母线进线方式Publiccommunicationbusentrymode图6.4.7公共交流母线进线方式的三相交－交变频电路原理图Fig.6.4.7SchematicdiagramofthreephaseAC-ACfrequencyconversioncircuitofpublicacbusinputmode

由三组彼此独立的，输出电压相位相互错开120

0的单相交-交变频电路组成。Itiscomposedofthreeindependentsingle-phaseACinvertercircuitswithoutputvoltageandphasestaggeredby120

0.

电源进线通过进线电抗器接在公共的交流母线上。ThepowerintakeisconnectedtothecommonACbusthroughtheintakereactor.

电源进线端公用,故三相单相变频电路的输出端必须隔离，为此，交流电动机的三个绕组必须拆开，同时引出六根线。Theinputlineofthepowersupplyiscommon,sotheoutputendofthethree-phasesingle-phasefrequencyconversioncircuitmustbeisolated.Forthis,thethreewindingsoftheACmotormustbedisassembledandsixwiresdrawnatthesametime.

主要用于中等容量的交流调速系统。MainlyusedinmediumcapacityACspeedcontrolsystem6.2ACtoACfrequencyconversioncircuit交交变频电路三相输出交－交变频电路ThreephaseoutputAC-ACfrequencyconversioncircuit

2.输出星形联结方式Outputstarconnectionmode

图6.4.8输出星形联结方式的三相交－交变频电路原理图Fig.6.4.8SchematicdiagramofthreephaseAC-ACfrequencyconversioncircuitwithoutputstarconnectionmode

三组的输出端和电动机的三个绕组都是星形联结；Theoutputendofthethreegroupsandthethreewindingsofthemotorareallstarconnection;

电动机中点和变频器中点接在一起，电动机只引三根线即可；Themidpointofthemotorandthemidpointofthefrequencyconverterareconnectedtogether,andthemotoronlyleadsthreelines.

三组单相变频器连接在一起，其电源进线必须隔离，所以分别用三个变压器供电；Threegroupsofsingle-phasefrequencyconvertersareconnectedtogether,andthepowersupplylinemustbeisolated,sothreetransformersarerespectivelyusedforpowersupply;

由于变频器输出中点不和负载中点相联结，所以在构成三相变频器的六组桥式电路中，至少要有不同相的两组桥中的四个晶闸管同时导通才能构成回路，形成电流；Becausetheoutputmidpointofthefrequencyconverterisnotconnectedwiththeloadmidpoint,sointhesixgroupsofbridgecircuitofthethree-phasefrequencyconverter,atleastfourthyristorsinthetwogroupsofdifferentphasesofthebridgeshouldconductatthesametimetoformacircuitandformacurrent;

同一组桥内的两个晶闸管靠双脉冲保证同时导通。两组桥之间依靠足够的脉冲宽度来保证同时有触发脉冲。TwothyristorsinthesamesetofBridgesareoperatedsimultaneouslybydoublepulses.ThepulsewidthbetweenthetwoBridgesissufficienttoensuresimultaneoustriggeringpulses.6.2ACtoACfrequencyconversioncircuit交交变频电路三相输出交－交变频电路ThreephaseoutputAC-ACfrequencyconversioncircuit

交－交变频电路输出频率上限的限制ThelimitontheupperlimitoftheoutputfrequencyofAC-ACfrequencyconversioncircuit

输出频率升高时，输出电压一个周期内电网电压的段数就减少，所含的谐波分量就要增加从而使输出电压波形畸变。Whentheoutputfrequencyincreases,thenumberofsegmentsofthenetworkvoltageinonecycleoftheoutputvoltagewilldecrease,andtheharmoniccomponentcontainedwillincrease,thusdistortingtheoutputvoltagewaveform.

一般的，交流电路采用6脉波的三相桥式电路时，最高输出频率不高于电网频率的1/3～1/2。电网频率为50HZ，交－交变频电路的输出上限频率约为20Hz。Generally,whentheACcircuitusesthethree-phasebridgecircuitwith6pulsewaves,thehighestoutputfrequencyisnothigherthan1/3~1/2ofthegridfrequency.Thegridfrequencyis50Hz,andtheoutputupperlimitfrequencyoftheAC-ACinvertercircuitisabout20Hz.6.2ACtoACfrequencyconversioncircuit交交变频电路

交－交变频器的优缺点AdvantagesanddisadvantagesofAC-ACinverter

优点Advantages

只有一次变流，且使用电