太陽能光伏并網逆變器設計原文及翻譯

Grid-ConnectedSolarMicroinverterReferenceDesignAbstract-Intraditionalgrid-connectedPVsystem,it’shardtoremovefailureofindividualPVpanels.ThispaperpresentsaSolarPVGrid-ConnectedMicro-inverterwhichcanbeembeddedinasinglestand-alonephotovoltaicpaneltosolvetheproblemofsinglepointoffailure.Forasinglephotovoltaicpanel,ratedpoweroftheMicro-inverteris220W,usingthetopologyofinterleavedflybackconverter.Keywords-Micro-inverter;interleavedflybackconverter;grid-connected;PVpanelI.INTRODUCTIONWiththedrainingoffossilfuelandincreasinglyseriouspollutioncausedbytraditionalpowergenerationmethodsacrosstheworld,renewableandpollution-freeenergyhasgainedmuchattentionineconomicandpoliticalfields.Renewableenergyincludesphotovoltaic(PV)andwindpowergenerationsystems.Wideapplicationofrenewableenergyisnowimpededbycostandextensiveresearchesshallbeconductedinordertoimprovecosteffectiveness.PVsystem,alsoknownassolarconverter,hasgainedpopularityinrecentyearsasaconvenientrenewableenergywithgoodprospects.HighproductioncostandlowconversionefficiencyofsiliconsolarpanelaremajordefectsofPVenergy.CosteffectivenessofPVprojectswillbecomemorereasonablewiththeapplicationofnewPVpanelproductiontechnologyandtheimprovementofconverterefficiency.??.EVOLUTIONOFPVSYSTEMA.TraditionalGrid-connectedSystemTraditionalgrid-connectedPVsystemiscomprisedof:UrbanHomeSystem–multiplesolarpanelsareconnectedinserialtosupply200-400VDCandoutputmediumpower(2-10KW)ACelectricity.IfcertainPVpanelintheseriesloopisdamaged(i.e.singlepointoffailure),theentiresystemwillbecrashed,i.e.thesystemisunstableSingleInverterWithMultipleDC/DCConverters–multiplePVpanelsareconnectedinparallelafterDC/DCconversiontoinputtotalDCbusbarvoltagetoinverterandincreaseoutputpower.SuchcircuitstructurealsohasproblemofsinglepointoffailuremeanwhilefusionofDCpowersupplyisverycomplex.UrbanHomeSystemWithStringInverters–PVpanelproviding200-400VinputDCvoltageisconnectedtomultipleparallelinverterstogeneratemediumpower(2-10KW)120/240VACpowersupply.Multipleparallelinverterscanboostoutputpowerandimprovesystemreliability.B.PVGrid-connectedMicro-inverterBasedontheaboveadvantagesanddisadvantagesofPVsystem,thepresentpaperproposesthedesignofPVgrid-connectedmicro-invertertoenableallPVpanelsinPVsystemtobeembeddedingrid-connectedmicro-inverter,seefigure1forsystemstructure.Micro-inverterwithsuchstructurehasfollowingadvantages:?replacecentralinverterwithdistributedinvertertooptimizeenergyutilization;?IntegratedPVpanelreducesinstallationcost;?Powerofmicro-inverterislow(hundredsW),resultingnlowinternaltemperatureandlongersystemservicelife,meanwhilefanisnotrequired.III.DESIGNOFPVGRID-CONNECTEDINVERTERThepresentpaperdesignsasinglestagePVgrid-connectedmicro-inverter.Asimpleinterleavedflybackconverterisappliedtooutputsinehalf-wavecommutatingvoltageandcurrent,passthroughbridgeinvertertooutputfullwavesinevoltageandcurrentandmakethecurrenthavethesamefrequencyandphaseofthepowergridvoltage.ThisPVgrid-connectedmicro-invertermatcheswithanyPVcomponentswith220Wpowerrating,25-45Voutputvoltageandupto55Vopen-circuitvoltage.A.SystemChartPVgrid-connectedmicro-inverterappliesparallelinterleavedflybackconverter,seefigure2.Ipri1iscurrentofflyback1converterMOSFETandIsec1iscurrentofflyback1outputdiode.Currentofsecondarydiode(Isec1)generatessinusoidaloutputvoltageafterbeingfilteredbyoutputfiltercapacitor.Theinvertermakesoutputcurrentsynchronouswithgridvoltagewithdigitalphase-lockedloop(PLL)technology.Themaximumpowertracksandcontrolstheoutputcurrent.VoltageoutputbyPVpanelisconvertedintosinehalf-wavecommutatingvoltage/currentbyinterleavedflybackconverter,inputsfull-bridgeinvertercircuitwhereitisinvertedintocurrentwiththesamephaseofgridvoltage,andisconnectedtopowergridafterEMC/EMIfiltration.Dutyratioflybackconverterswitchshallbecontrolledtomaketheoutputcurrenthavethesamephaseandfrequencywithgridvoltage.Interleavedflybackconverterimprovesservicelifeofcapacitorbyreducingtheeffectivevalueofinputlargeelectrolyticcapacitorripplecurrent.Interlacedoutputreducesoutputcurrentripplesoastodecreasetotalharmonicdistortionofcurrent.B.CircuitAnalysisPVpanelDCvoltageinputsinterleavedflybackconverteranddrivesflybackMOSFETtogeneratesineoutputvoltage/currentwithHFsinePWNmodulatingsignal.Phasedifferencebetweentwointerleavedflybackconverterdrivingsignalsis180degree.Interleavedflybacktopologystructureworksundertwoswitchmodes.?Mode1:whenflybackMOSFETisopened,HFflybacktransformerprimarymagneticinductoraccumulatesenergy,diodeisphasereversalblockedandthesecondarytransformerwindingvoltageisreversebiased.Duringthatperiod,primaryinductorofHFflybacktransformerislikeapowerinductor,primarycurrent(Ipri1/Ipri2)ascendslinearlyandloadcurrentisfromoutputcapacitor.Mode2:whenflybackMOSFETisclosed,voltageofprimarywindingisinphasereversalandoutputdiodeisforwardbiased.Energystoredatprimarywindingistransferredtosecondarywindingandprovidecurrenttooutputcapacitorandload.Duringthatperiod,outputvoltageisfromthesecondarytransformerwindingdirectlyandthenlinearityofdiodecurrentdecreases.SinePWMmodulatingsignaldrivesMOSFETtogenerateprimarycurrentandthengeneratecurrentatthesecondarydiode.Half-wavesineaveragecurrentofsecondaryrectifierdiodegeneratesstandardhalf-wavesinevoltage/currentthroughoutputcapacitorfiltration.Controllablesiliconfullbridgerectifiercircuitisusedtoproducesine-basedoutputhalf-wavesinevoltage/current.Thereby,thecontrollablesiliconswitchesfrequencyintopowergridfrequency.Inputvoltage/currentwaveformofinputvoltageandsolarmicro-inverterinfrontofSCRbridgecircuitandoutputvoltage/currentwaveformofsolarmicro-inverterareshowninfigure3.C.ControlCircuitPVgrid-connectedmicro-invertercontrolsystemconsistoffollowingcontrolcircuits:digitalphase-lockedloop(PLL),currentcontrolcircuit,maximumpowertrackingcircuitandloadbalancecontrolcircuit.PLLandcurrentcontrolcircuitrelatedtogrid-connectedcontrolarediscussedinthepresentpaperonly.1)Digitalphase-lockedloop(PLL)PLLcontrolsystemisacrucialcomponentofcontrolsystemtoenableelectricenergyoutputbythesystemtobeconnectedtopowergridinunitpowerfactor.PLLmakesinverteroutputcurrenthavethefrequencyandphaseanglesynchronouswithgridvoltage.ADCchannelofthesoftwaresamplesgridvoltageandinverteroutputcurrentsignalandsavespolarityofgrid-connectedvoltageinregisterhencepolarityofgridvoltageisclearduringeachsamplingperiod.Zero-voltagedetectionmarkissetbythesoftwarewhenpolarityofgridvoltagevaries.Whengridvoltagepasseszerocrossingpoint,theinputtimerinterruptsandwaitsforthenextzerocrossingpoint,andcountofthetimerduringtheinterruptionbetweentwozerocrossingpointsishalfoftheperiodvalueofgridvoltage.Periodvaluecanbeusedtoexpressgridfrequencyanddecidesphaseangleincrementincitingofsinetablereferencevalues.Frequencyandphaseofgridvoltageandinverteroutputcurrentcanbeacquiredwiththeabovesamplingparameters,andrelevantSPWMcarrierfrequencyandinitialphaseareregulatedaccordingthecalculationresultstoenablePVinvertersystemoutputcurrenttotrackfrequencyandphaseofgridvoltage.Thesinetablecovers512referenceelementsofsine0through90degree.2)CurrentcontrolcircuitCurrentcontrolcircuitappliesPIcontrollerandisthecoreofcontrolsystem.OutputcontrolsignalofcurrentcontrolcircuitcontrolsdutyratioofflybackMOSFET(D)toensurethatinputcurrentIACfollowsreferencecurrentIACref.Equivalentnon-isolatedcircuitofflybackconverteractsasabuck-boostconverter;thereforebuck/boostconvertercanbeusedtoestablishmodelandcalculatecontrolcircuitparameters.Likebuck/boostconverterisahighlynonlinearsystemlikeboostconverter.Outputvoltageandcurrenthavenonlinearrelationwiththedutyratiowhenthesystemoperatesundercontinuousconductionmode.ThecurrentchallengeishowtocontrolthedutyrationofflybackMOSFETDandgenerateasinusoidalcurrent.Circuitofbuck/boostconverterisshowninfigure4.Magneticinductorofflybackisreplacedbyabuck-boostinductor.GivingdutyratioDtoswitchistogeneratesinusoidalcurrentpassingload.Thebuck/boosttopologystructuregeneratesreversevoltage.Therefore,averagecurrentthroughdiodeandloadshouldbelikeamodifiedsinewaveupsidedown.Asthecurrentofinductordoesnotchangeinstantly,loadcurrentcanbecalculatedwiththefollowingformula.ILOADrepresentsthecurrentofflybackinvertersystem;IAC,ILrepresentsthecurrentpassingflybackcurrentmagneticconverter;IL*representsIACrefreferencecurrent;DrepresentsdutyratioofflybackMOSFET;GiscoefficientofcontrolcircuitcompensationcircuitKpandKi.Fundamentalformulaofinductorcanbeexpressedbyformula2.It’sunliketoobtaincurrentparametersdirectlyinsteadcurrenterrorproportionaltovoltageisusedtocontrolcurrentasshowninformula3.Accordingtobasicpowerelectronicstheory,Vx=Vin*D-(1-D)*VoOutputvoltageofflybackcircuitVoishalf-waverectifiedsinusoidalvoltageandisconnectedtopowergridthroughthyristorfullbridgeinverter.DutyratioDiscalculatedbyformula4withinputvoltageVinandoutputvoltageVomeasured.Formula5istherelationexpressionbetweeninputvoltageandoutputvoltageofbuck/boostconverter.Desireddutyratiocanbecalculatedwithformulae4and5asshowninformula6,whereIload*ismodifiedsinewave.ThefirstitemisthecalculationresultofPIcompensatorofwhichbandwidthisgivenbyG/L.Theseconditemistheresultofopenloopcontrolwiththepurposeofenablingcurrenttooutputinsinewavewithoutcontrol.IV.SYSTEMSIMULATIONA.A.SimulinkSimulationModelBasedontheaboveanalysis,thepresentpaperestablishesSimulinkdigitalsimulationmodelofPVgrid-connectedmicro-inverterwiththegeneralflowchartshowninfigure5,where,Vin_ref-secondary1isPVpaneloutputvoltage;Subsystem2outputsreferencecurrentandgridvoltage;Subsystem3ismodelofflybackconverterwithinternalflowchartasshowninfigure6;andcontroller1isflowchartofcontrolcircuitandincludesPLLcontrolandaveragecurrenttrackingcontrolasshowninfigure6.B.SimulationResultandAnalysisBasedontheabovesimulationmode,whenPVinputvoltageissettoVinto25V,referenceinputissetto1A/50HZsinecurrentandgridvoltageVgridissetto220V,waveformofoutputcurrentinfrontofSCRfullbridgeinverteracquiredisasshowninfigure7,andoutputcurrentwiththesamemagnitudewithreferencecurrentandthesamephasewithgridvoltageisobtainedafterthesaidcurrentpassesthroughfullbridgeinverter.Theupperpartofthefigureisthewaveformofreferencecurrentandthelowerpartisthewaveformofoutputcurrent.Accordingtosimulationresult,outputcurrentofthesystemhasthesamephasewithreferencecurrentsignal;correctnessofthecontrolmethodisvalidated.V.CONCLUSIONThispaperpresentsaninnovativePVgrid-connectedmicro-inverterwith220WpowerratingandcanbeusedbycombiningwithindividualPVpanelsintomodulesoastoshoottroubleofsinglepointoffailureofindividualPVpanelsinPVgrid-connectedpowergenerationsystemandimprovesgeneratingefficiency.Thisinverterappliesinterleavedflybacktransformertopologyfallingintosingle-phaseinverterstructurewhichissimpleandefficient.Thepaperalsostudiesgrid-connectedcontrolmethodandcurrentcontrolmethodinresponsetotheinvertertopologystructureandestablishessimulationmodeltovalidatethecorrectnessofthedesign.太陽能光伏并網逆變器設計一、引言與排水的化石燃料，由傳統(tǒng)的發(fā)電方式，在世界各地造成了日益嚴重的污染，可再生、無污染的能源在經濟和政治領域備受關注?？稍偕茉粗饕ㄌ柲芄夥睵V〕和風力發(fā)電系統(tǒng)?？稍偕茉吹膹V泛應用是現(xiàn)在的本錢和廣泛的研究，阻礙了應當以提高本錢效益。太陽能光伏發(fā)電系統(tǒng)，也被稱為太陽能轉換器，已經獲得了普及，近年來作為一種方便的可再生能源，具有良好的應用前景。生產本錢高，硅太陽能板的轉換效率低的光伏能源的重大缺陷。光伏工程的本錢效益將更加合理的新的光伏面板生產技術應用和轉換效率的提高。二、PV系統(tǒng)的開展A.傳統(tǒng)的PV系統(tǒng)傳統(tǒng)的光伏并網發(fā)電系統(tǒng)是由：城市家庭系統(tǒng)–多個太陽能電池板串聯(lián)供給200-400v直流輸出功率〔2-10kw〕交流電力。如果在串聯(lián)回路一定光伏電池板損壞〔即單點故障〕，整個系統(tǒng)將崩潰，即系統(tǒng)是不穩(wěn)定的。單逆變器多直流/直流轉換器–多個光伏電池板并聯(lián)在直流/直流轉換輸入總的直流母線電壓逆變器和提高輸出功率。這種電路結構也有失敗，同時融合的直流電源的單點問題是很復雜的。串逆變器–光伏面板提供200-400v輸入直流電壓的城市家庭系統(tǒng)連接到多個并聯(lián)逆變器產生中等功率〔2-10kw〕120/240V交流電源。多臺逆變器并聯(lián)可以提高輸出功率和改善系統(tǒng)的可靠性。B.光伏并網微逆變器基于以上優(yōu)點，光伏系統(tǒng)的缺點，本文提出了光伏并網微逆變器的設計，使光伏系統(tǒng)中所有的太陽能光伏板被嵌入在電網連接的微逆變器，看到系統(tǒng)結構圖1。這種結構的微逆變器具有以下優(yōu)點：?取代中央逆變器分布式逆變器優(yōu)化能源利用；?集成光伏面板降低安裝本錢；?微逆變器功率低〔幾百W〕，而N低的內部溫度和較長的系統(tǒng)的使用壽命，同時風機是不需要的。三、設計光伏并網發(fā)電逆變器本文設計了一個單級光伏并網微逆變器。一個簡單的交錯反激變換器應用于輸出正弦半波整流電壓和電流，通過橋逆變器輸出全波正弦電壓和電流，使電流具有相同的頻率和電網電壓相位。這種光伏并網微逆變器與任何光伏組件與220W功率，25-45v輸出電壓到55V的開路電壓。A.系統(tǒng)圖光伏并網微功率逆變器應用了并聯(lián)交錯反激式逆變器，見圖2Ipri1是flyback1逆變電路MOSFET的電流和Isec1是flyback1輸出的二極管的電流。次級二極管〔Isec1〕的電流被濾波電容后過濾后輸出，產生的正弦輸出電壓。逆變器通過數(shù)字鎖相環(huán)〔PLL〕技術，使輸出的電流同步與電網電壓。最大功率跟蹤和控制輸出電流。由光伏面板輸出的電壓，通過交錯反激式轉換器，被轉換成正弦半波整流電壓/電流，輸入全橋反相電路。全橋反相電路將電流變換為與電網電壓的相位相同，并經過EMC/EMI的過濾后連接到電網。反激逆變器開關的占空比應加以控制，以使輸出電流與電網電壓的相位和頻率相同。交錯反激轉換器提高電容器的使用壽命通過減少輸入大電解電容的紋波電流的有效值。隔行輸出降低了輸出電流的紋波，從而減小電流的總諧波失真。B.電路分析光伏電池的直流電壓輸入進了交錯反激變換器，并且驅動反激電路的MOSFET產生正弦輸出電壓/電流。MOSFET是被高頻正弦PWM調制信號調制的。兩個交錯反激變換器的驅動信號的相位差是180度。交錯的反激式拓撲結構在兩種開關模式下工作。模式1：當flyback電路的MOSFET被翻開時，高頻flyback電路的變壓器的初級側電感器磁蓄積能量，二極管反相截止和次級變壓器繞組的電壓是反向偏置。在此期間，反激式高頻變壓器初級側的電感就像一個功率電感，初級電流〔Ipri1/Ipri2〕線性上升和負載電流來自于輸出電容。模式2：當反激電路的MOSFET閉合時，初級繞組的電壓的相位反轉和輸出二極管被正向偏置。儲存在初級繞組的能量轉移到次級繞組，并提供給輸出電容和負載電流。在此期間，輸出電壓直接來自變壓器次級側的繞組，并且二極管上的電流線性減小。正弦PWM調制信號直接驅動MOSFET產生初級電流，然后產生電流在會流過次級側二極管。次級側的正弦半波平均電流在經歷了次級側的整流二極管后產生標準的半波正弦電壓/電流，通過輸出電容過濾。可控硅全橋整流電路，用于產生正弦波，而這種正弦波是基于半波正弦電壓/電流而產生的。由此，可控硅開關頻率為電網頻率。輸入電壓和太陽能微功率逆變器在可控硅橋電路之前的的輸入電壓/電流的波形和太陽能微逆變器波形的輸出電壓/電流如圖3所示。C.控制電路光伏并網微逆變器控制系統(tǒng)包括以下控制電路：數(shù)字鎖相環(huán)〔PLL〕，電流控制電路，最大功率跟蹤電路和負載平衡控制電路。本文僅僅討論鎖相環(huán)和電流控制電路中和并網控制有關的局部。1〕數(shù)字鎖相環(huán)〔PLL〕，PLL鎖相控制系統(tǒng)是控制系統(tǒng)的一個非常重要的組成局部，使得系統(tǒng)輸出的電能連接到電力網中的單元功率因數(shù)。PLL使逆變器輸出電流具有的頻率和相位角同步與電網電壓。軟件樣本電網電壓和逆變器輸出電流信號的ADC通道和保存了與電網連接電壓的極性在存放器，因此電網電壓的極性在每個采樣周期都是明顯的。零電壓檢測標記是由軟件設置的，當電網電壓的極性發(fā)生變化時標記。當電網電壓過零點，輸入定時器中斷等待下一個零點，二零點之間的中斷時間的定時器計數(shù)是電網電壓的周期值的一半。周期值可以用來表達電網頻率和決定相位角增量，通