外文文献及翻译-sinusoidal pulse width modulation

本科毕业设计论文外文翻译专业电气工程及其自动化所在学院电子信息工程学院二零一二年六月24437POWERELECTRONICSSINUSOIDALPULSEWIDTHMODULATIONTHESWITCHESINTHEVOLTAGESOURCEINVERTERSEEFIG1CANBETURNEDONANDOFFASREQUIREDINTHESIMPLESTAPPROACH,THETOPSWITCHISTURNEDONIFTURNEDONANDOFFONLYONCEINEACHCYCLE,ASQUAREWAVEWAVEFORMRESULTSHOWEVER,IFTURNEDONSEVERALTIMESINACYCLEANIMPROVEDHARMONICPROFILEMAYBEACHIEVEDFIG1SIMPLEVOLTAGESOURCEDINTHEMOSTSTRAIGHTFORWARDIMPLEMENTATION,GENERATIONOFTHEDESIREDOUTPUTVOLTAGEISACHIEVEDBYCOMPARINGTHEDESIREDREFERENCEWAVEFORMMODULATINGSIGNALWITHAHIGHFREQUENCYTRIANGULARCARRIERWAVEASDEPICTEDSCHEMATICALLYINFIG2DEPENDINGONWHETHERTHESIGNALVOLTAGEISLARGERORSMALLERTHANTHECARRIERWAVEFORM,EITHERTHEPOSITIVEORNEGATIVEDCBUSVOLTAGEISAPPLIEDATTHEOUTPUTNOTETHATOVERTHEPERIODOFONETRIANGLEWAVE,THEAVERAGEVOLTAGEAPPLIEDTOTHELOADISPROPORTIONALTOTHEAMPLITUDEOFTHESIGNALASSUMEDCONSTANTDURINGTHISPERIODTHERESULTINGCHOPPEDSQUAREWAVEFORMCONTAINSAREPLICAOFTHEDESIREDWAVEFORMINITSLOWFREQUENCYCOMPONENTS,WITHTHEHIGHERFREQUENCYCOMPONENTSBEINGATFREQUENCIESOFANCLOSETOTHECARRIERFREQUENCYNOTICETHATTHEROOTMEANSQUAREVALUEOFTHEACVOLTAGEWAVEFORMISSTILLEQUALTOTHEDCBUSVOLTAGE,ANDHENCETHETOTALHARMONICDISTORTIONISNOTAFFECTEDBYTHEPWMPROCESSTHEHARMONICCOMPONENTSAREMERELYSHIFTEDINTOTHEHIGHERFREQUENCYRANGEANDAREAUTOMATICALLYFILTEREDDUETOINDUCTANCESINTHEACSYSTEMWHENTHEMODULATINGSIGNALISASINUSOIDOFAMPLITUDEAM,ANDTHEAMPLITUDEOFTHETRIANGULARCARRIERISAC,THERATIOMAM/ACISKNOWNASTHEMODULATIONINDEXNOTETHATCONTROLLINGTHEMODULATIONINDEXTHEREFORCONTROLSTHEAMPLITUDEOFTHEAPPLIEDOUTPUTVOLTAGEWITHASUFFICIENTLYHIGHCARRIERFREQUENCYSEEFIG3DRAWNFORFC/FM21ANDTL/RT/3TPERIODOFFUNDAMENTAL,THEHIGHFREQUENCYCOMPONENTSDONOTPROPAGATESIGNIFICANTLYINTHEACNETWORKORLOADDUETHEPRESENCEOFTHEINDUCTIVEELEMENTSHOWEVER,AHIGHERCARRIERFREQUENCYDOESRESULTINALARGERNUMBEROFSWITCHINGSPERCYCLEANDHENCEINANINCREASEDPOWERLOSSTYPICALLYSWITCHINGFREQUENCIESINTHE215KHZRANGEARECONSIDEREDADEQUATEFORPOWERSYSTEMSAPPLICATIONSALSOINTHREEPHASESYSTEMSITISADVISABLETOUSESSOTHATALLTHREEWAVEFORMSARESYMMETRICFIG2PRINCIPALOFPULSEWIDTHMODULATIONFIG3SPWMWITHFC/FM48,L/RT/3NOTETHATTHEPROCESSWORKSWELLFORM1FORM1,THEREAREPERIODSOFTHETRIANGLEWAVEINWHICHTHEREISNOINTERSECTIONOFTHECARRIERANDTHESIGNALASINFIG4HOWEVER,ACERTAINAMOUNTOFTHIS“OVERMODULATION”ISOFTENALLOWEDINTHEINTERESTOFOBTAININGALARGERACVOLTAGEMAGNITUDEEVENTHOUGHTHESPECTRALCONTENTOFTHEVOLTAGEISRENDEREDSOMEWHATPOORERNOTETHATWITHANODDRATIOFORFC/FM,THEWAVEFORMISANTISYMMETRICOVERA360DEGREECYCLEWITHANEVENNUMBER,THEREAREHARMONICSOFEVENORDER,BUTINPARTICULARALSOASMALLDCCOMPONENTHENCEANEVENNUMBERISNOTRECOMMENDEDFORSINGLEPHASEINVERTERS,PARTICULARLYFORSMALRATIOSOFFC/FMSPWMSPECTRAALTHOUGHTHESPWMWAVEFORMHASHARMONICSOFSEVERALORDERSINTHEPHASEVOLTAGEWAVEFORM,THEDOMINANTONESOTHERTHANTHEFUNDAMENTALAREOFORDERNANDN2WHERENFC/FMTHISISEVIDENTFORTHESPECTRUMFORN15ANDM08SHOWNINFIG5NOTETHATIFTHEOTHERTWOPHASESAREIDENTICALLYGENERATEDBUT120OAPARTINPHASE,THELINELINEVOLTAGEWILLNOTHAVEANYTRIPLENHARMONICSHENCEITISADVISABLETOCHOOSE,ASTHENTHEDOMINANTHARMONICWILLBEELIMINATEDITISEVIDENTFROMFIG5B,THATTHEDOMINANT15THHARMONICINFIG5AISEFFECTIVELYELIMINATEDINTHELINEVOLTAGECHOOSINGAMULTIPLEOF3ISALSOCONVENIENTASTHENTHESAMETRIANGULARWAVEFORMCANBEUSEDASTHECARRIERINALLTHREEPHASES,LEADINGTOSOMESIMPLIFICATIONINHARDWAREITISREADILYSEENTHATASTHEWHEREEISTHEDCBUSVOLTAGE,THATTHERMSVALUEOFTHEOUTPUTVOLTAGESIGNALISUNAFFECTEDBYTHEPWMPROCESSTHISISSTRICTLYTRUEFORTHEPHASEVOLTAGEASTRIPLENHARMONICORDERSARECANCELLEDINTHELINEVOLTAGEHOWEVER,THEPROBLEMATICHARMONICSARESHIFTEDTOHIGHERORDERS,THEREBYMAKINGFILTERINGMUCHEASIEROFTEN,THEFILTERINGISCARRIEDOUTVIATHENATURALHIGHIMPEDANCECHARACTERISTICOFTHELOADFIG5SPWMHARMONICSPECTRAN15,M0SELECTIVEHARMONICELIMINATIONALSOCALLEDOPTIMALPWMNOTICETHATINTHESPWMSTRATEGYDEVELOPEDABOVE,ALARGENUMBEROFSWITCHINGSAREREQUIRED,WITHTHECONSEQUENTASSOCIATEDSWITCHINGLOSSESWITHTHEMETHODOFSELECTIVEHARMONICELIMINATION,ONLYSELECTEDHARMONICSAREELIMINATEDWITHTHESMALLESTNUMBEROFSWITCHINGSTHISMETHODHOWEVERCANBEDIFFICULTTOIMPLEMENTONLINEDUETOCOMPUTATIONANDMEMORYREQUIREMENTSFORATWOLEVELPWMWAVEFORMWITHODDANDHALFWAVESYMMETRIESANDNCHOPSPERQUARTERCYCLEASSHOWNINFIG4,THEPEAKMAGNITUDEOFTHEHARMONICCOMPONENTSINCLUDINGTHEFUNDAMENTALAREGIVENBYEQN1HEREISTHEMAGNITUDEOFTHEHARMONICANDISTHEPRIMARYSWITCHINGANGLEEVENHARMONICSDONOTSHOWUPBECAUSEOFTHEHALFWAVESYMMETRYTHENCHOPSINTHEWAVEFORMAFFORDNDEGREESOFFREEDOMSEVERALCONTROLOPTIONSARETHUSPOSSIBLEFOREXAMPLENSELECTEDHARMONICSCANBEELIMINATEDANOTHEROPTIONWHICHISUSEDHEREISTOELIMINATEN1SELECTEDHARMONICSANDUSETHEREMAININGDEGREEOFFREEDOMTOCONTROLTHEFUNDAMENTALFREQUENCYACVOLTAGETOFINDTHESREQUIREDTOACHIEVETHISOBJECTIVE,ITISSUFFICIENTTOSETTHECORRESPONDINGHSINTHEABOVEEQUATIONSTOTHEDESIREDVALUES0FORTHEN1HARMONICSTOBEELIMINATEDANDTHEDESIREDPERUNITACMAGNITUDEFORTHEFUNDAMENTALANDSOLVEFORTHESFIG4ATWOLEVELPWMWAVEFORMWITHODDANDHALFWAVESYMMEQUATION1CANBEREADILYPROVEDBYFINDINGTHEFOURIERCOEFFICIENTSOFTHEWAVEFORMSHOWNINFIG4INGENERAL,FORAPERIODICWAVEFORMWITHPERIOD,THEFOURIERCOSINEANDSINECOEFFICIENTSAREGIVENBYBECAUSEOFTHEHALFCYCLESYMMETRYOFTHEWAVEFORMOFFIG4,ONLYODDORDERHARMONICSEXISTALSO,ITISEASYTOSEETHATTHEFOURIERCOSINECOEFFICIENTSDISAPPEARWITHTHECHOICEOFCOORDINATEAXESUSEDUTILIZINGTHEQUARTERCYCLESYMMETRY,THEFOURIERSINECOEFFICIENTSBECOMESUBSTITUTINGTHETWOVALUEDPWMWAVEFORMFOR,ONEOBTAINSSEEFIG4THEFOLLOWINGEXAMPLEILLUSTRATESTHEUSEOFTHREECHOPSPERQUARTERCYCLEWHICHALLOWFORTHREEDEGREESOFFREEDOMWEMAYUSETHESETOELIMINATETWOHARMONICSANDCONTROLTHEMAGNITUDEOFTHEFUNDAMENTALTOANYDESIREDVALUEEXAMPLESELECTIVEHARMONICELIMINATIONISAPPLIEDWITHAVIEWTOCONTROLLINGTHEFUNDAMENTALCOMPONENTOFVOLTAGETO50VRMSANDELIMINATINGTHE3RDAND5THHARMONICSTHESOURCEVOLTAGEIS100VCALCULATETHEREQUIREDCHOPPINGANGLESASTHREEOBJECTIVESARETOBEACHIEVED,WENEED3CHOPSTHEFUNDAMENTAL,3RDAND5THHARMONICMAGNITUDESAREGIVENBYWEREQUIRE翻译24437电力电子正弦脉宽调制电压源逆变器的开关（见图1）可以按要求打开和关闭。用最简单的方法，顶部的开关打开，如果每个周期打开和关闭，方波的波形结果只有一次。但是，如果改进谐波的数据则在一个周期内可以形成多次打开关闭。图1简单的电压源逆变器在最直接的实现方式，所期望的输出电压生成是通过比较预期的参考波形与高频率三角载体波（调制信号）所描述的图2根据信号电压是否大于或小于载体波波形，无论是正还是负的直流母线电压施加在输出。注意，在此期间一个三角波周期的平均电压加到负载型成正比（假定不变），信号的振幅。注意,经过一段时期一个三角形波,平均电压的负荷是成正比的幅值的信号假定常数在这个时期。由此产生的方波包含在它的低频率元件所需波形的复制，具有较高频率分量在一个载波频率接近的频率的福祉。注意，均方根平方的交流电压波形值仍相等的直流母线电压，由于PWM使得总谐波不失真。谐波成分只是转移到更高的频率范围，并且由于电感的交流系统自动地过滤。当调制信号为正弦波的振幅AM，和三角载波的振幅AC的比AM/AC是已知的调制指数。注意，控制调制指数为施加控制输出电压幅值。具有足够高的载波频率（参见图3得出FC/FM21ANDTL/RT/3；T基础时期），由于感性元件的存在高频成分明显不传播到交流网络（或负载）。然而，由于较高的载波频率，开关较多从而在每个周期不增加功率损耗。电力系统的应用通常在215KHZ的开关频率范围被认为是足够的。此外，在三相系统中，建议使用使所有三个波形对称。图2主要的脉宽调制图3SPWM的FC/FM48，L/RT/3注意，这个过程很适合。因为在图4中有三角波其中有没有交际的载体作为信号周期。然而，这种“过调制”在一定量往往是允许获得更大的交流电压，使电压频谱呈现稍差。注意，FC/FM使用一个额外的比率，波形是反周期超过360度的对称。随着偶数阶谐波，特别小的直流元件。因此一个单相逆变器的不推荐用偶数，特别是FC/FM额外比率。SPWM的频谱虽然SPWM波形已在几个数量相电压波形的谐波，比其他有根本优势，是因为当NFC/FM，N和N正负2。这是经济脆弱性，在图5削弱了频谱对N15和M08。请注意，如果其他两个阶段产生的，但除了在相同阶段120O，先电压不会有任何。因此它选择是明智的。正如当时占主导地位的谐波将被淘汰。它是由图5B自明的，占主导地位的第15谐波，图5A有效地消除了线路电压。选择3的倍数也方便，则相同的特里安奇异波形可作为承运的所有三个阶段，可