中英文文献翻译-测量单相电能质量参数的数字表的设计和样机研制

DesignandPrototypeDevelopmentofADigitalInstrumentforMeasuringSinglePhasePowerQualityParametersSriramKarakanaElectricalandElectronicsEngineeringGVPCollegeofEngineering(A)Visakhapatnam,AP,IAbstractInpresentpowersystem,themeasurementofpowerqualityisbecomingnecessaryduetothepresenceofnonlinearanddynamicloads.Thispaperproposesadigitalinstrument,designedandplementedashardwaretomeasurebasicsinglephasepowerqualityparameterslikevoltage,urrent,frequency,phaseangle,powerfactor,powerandtotalharmonicdistortion(THD).Theverypurposeofdesigningthishardwarecircuitistohaveknowledgeofmeasuringtheaboveelectricpowerqualityparametersandtoimprovethesystemperformance.ThebasicinputsforthisinstrumentarevoltageandcurrentsignalswhicharesensedbyaHallEffectvoltageandcurrenttransducers.Amicrocontrollerdevelopmentboard(MixedSignalProcessor)MSP430LaunchpadmanufacturedbyTexasInstrumentsisusedfordigitalprocessingofthetwosignals.AllsoftwarerelatedprogrammingiswritteninC-languagecodeinMSP430.A16x2LCDdisplayisusedfordisplayingthepowerqualityparameters.TheimplementedhardwarecircuitistestedwithstandardmetersinthelaboratoryandwithpowerqualitymeterCW240(Clamponmeter)manufacturedbyYOKOGAWAandtheresultoftheexperimentalworkdoneonaprototypeofapowerqualitymeasurementinstrumentisreported.IndexTermsPowerquality,TotalHarmonicDistortion,HallEffecttransducers,MSP430,CW240clamponmeter.NageswaraRaoNamburiProfessor,ElectricalandElectronicsEngineeringGVPCollegeofEngineering(A)Visakhapatnam,AP,Indianageswara.namburigvpce.ac.inI.INTRODUCTIONInpresentpowersystem,thegeneratingsourceswhicharecommonlyfeedingpowerintoelectricgridareroducingdisturbances.Mainlyrenewableenergysourceswhichcontainpowerelectronicconvertersareinjectingharmonicsasdisturbancesintoelectricgrid.Sothereisanecessityofmeasuringpowerqualityofasystembeforeitused.Thereisalsoanimpellingneedtomeasurepowerqualityparameterstoknowtheelectricalsystembehaviorwhichhelpsintakingmeasurestoimproveoverallsystemperformance.Thispaperroposesadigitalinstrumentdevelopedasprototypehardwareforasinglephasepowersystemtomeasurebasicpowerqualityparameterslikevoltage,current,frequency,phaseangle,powerfactor,powerandtotalharmonicdistortion(THD).Sincethemeterisdesignedforasinglephasepowersystem,asinglesetofcurrentandvoltagetransducersissufficient.Tomeasurevoltage,LV-25PHallEffectvoltagetransducerhavingarangeof0-500VmanufacturedbyLEMisused.Foreasuringcurrent,LA-100PHallEffectcurrenttransducerhavingarangeof0-100Aisused.BiasvoltagefortransducersisprovidedbyVoltageregulatorsLM7812andLM7912givingaregulatedpowersupplyof+12Vand-12Vrespectively.AMixedSignalProcessor(MSP430)LaunchpadmanufacturedfromTIisusedfordigitalprocessing.Algorithmsforharmonicanalysis,calculationofrootmeansquarevalues(RMS)functionsandremainingallsoftwarerelatedprogrammingarewritteninC-languagecodeinMSP430.Zerocrossingdetectorstomeasurefrequency,voltagefollowers(buffers)tostrengthensignal,inversioncircuittoinvertnegativehalfcycleintopositiveforADCSamplingaredevelopedbyusingasimpleoperationalamplifier(OP-AMP)circuitry.LM324,aquadchannelOP-AMPisusedforthisI.purpose.A16x2LCDdisplayisusedfordisplayingthepowerqualityparameters.Theimplementedhardwarecircuitistestedwithstandardmetersinthelaboratorylikeammeter,voltmeter,wattmeter,powerfactormeterandalsowiththepowerqualitymeterCW240(Clamponmeter)anufacturedbyYOKOGAWA.Thedevelopedprototypeinstrumentistestedthoroughlyinthelaboratoryandtheresultsarereportedaswellasobservationsarediscussed.II.HARDWARECONFIGURATIONTheblockdiagramoftheproposeddigitalinstrumentisshowninFig.1.ASinglephasepowersystemisindicatedinfigurebyLine(L)andNeutral(N).Theblockdiagrammainlyconsistsoffourparts.TheyareA)HallEffecttransducers.B)Signalconditioningcircuit.C)Digitalprocessingunit-MSP430Launchpad.D)16x2LCDDisplay.A.HallEffectTransducersTomeasureallkindsofpowerqualityparameters,thebasicinputsrequiredarevoltageandcurrent.Soinordertomeasurevoltageandcurrent,aHallEffectcurrentandvoltageTransducers(transducers)manufacturedbyLEMareusedinthisprototype.Thesetransducersaretestedandcalibratedwiththelaboratoryequipment.TheaboveFig.2indicatesvoltagetransducerwhichconsistsoftwoinputterminals(+HTand-HT),threeoutputterminals(+,-,M)andtworesistanceseachatinput(R1)andoutput(Rm).Inputterminals(+HTand-HT)areconnectedtolineandneutralofasinglephasesupplyrespectively.Outputterminals(+and-)areusedtogivepowertothetransducer.Theycanbeconnectedeitherto12Vor15V.Remainingoutputterminal(M)isconnectedtogroundthrougharesistanceRmandthevoltagedropacrossRmwillgivestheattenuatedvoltageofinputfromthetransducer.Calculationsforresistancesareasfollows.Primarynominalcurrent(IPN)=10mA.MaxVoltagethatcanbesensedbytransducer=500volts.Inputresistance(R1)=50kiloohms50k,5W.Secondarynominalcurrent(ISN)=25mA.Definedsecondaryvoltageoutput=0.5V.Outputresistance(Rm)=0.5V/25mA=20ohms20,0.25W.Fig.3.indicatescurrenttransducerwhichconsistsofthreeoutputterminals(+,-,M)andaresistanceatoutput(Rm).Itconsistsofahollowstructureinwhichsupplywireiswounded.Outputterminals(+and-)areusedtopowertransducer.Theycanbeconnectedeitherto12Vor15V.Remainingoutputterminal(M)isconnectedtogroundthrougharesistanceRmandthevoltagedropacrossRmwillgivestheattenuatedvoltagewhichisanalogoustocurrentmeasurement.Acalculationforresistanceisasfollows.Secondarynominalcurrent(ISN)=100mA.Definedsecondaryvoltageoutput=2V.Outputresistance(Rm)=2V/100mA=20ohms20,0.25W.B.SignalConditioningCircuitIngeneral,ifananalogsignalisintendedtogivetoadigitalprocessorlikeanADCoramicrocontroller,beforegivingitshouldbemanipulatedtomeettherequirementsofnextstageforfurtherprocessing.Thisiscalledassignalconditioning.Operationalamplifiers(OP-AMPS)arecommonlyemployedforthispurpose.Intheproposedprototype,threecircuitsarebuiltusingOPAMPcircuitry.Theyare1)ZeroCrossingDetector.2)Voltagefollower(Buffer).3)Invertingamplifier.1)ZeroCrossingDetectors:Thiscircuitisbuiltformeasuringfrequencyofawaveformwiththehelpofzerocrossingsshowninfig.4.Twoconsecutivezerocrossingsareidentifiedandtimeperiodbetweenthemgivestimeforahalfcyclewhichisusedtocalculatethefrequency.2)VoltageFollower(Buffer):ThiscircuitisusedforamplificationofanalogsignaltomeettherequirementsofADCandpreventsthesecondcircuitfromloadingthefirstcircuit.Becauseanidealoperationalamplifierhasinfiniteinputimpedanceandzerooutputimpedance.Ifgain(Av)ismadeas1,thenitiscalledasunitygainbufferoravoltagefollowerwhichisshowninfig.5.3)InvertingAmplifier:Itisusedforbothamplificationandinversionoftheanalogsignal.InproposedprototypetheADCiscapableofsamplingpositivehalfcycleonly.Soinordertoachievecompletesignalsampling,thenegativehalfcycleisinvertedintopositivewiththehelpofthisop-ampcircuit.Fig.6illustratesitsoperation.C.DigitalProcessingUnitDigitalprocessingUnitisaonewhichprocessesthedigitalsignalstoachieverequiredparameters.Inthisproposedprototype,MSP430F5529Launchpadisusedasadigitalprocessingunit.ThebasicfeaturesarelistedinFig.7.Itconsistsof16channels,12-bitsuccessiveapproximationtypeanalogtodigitalconverter(ADC)inwhichtwochannelsareusedforsamplingpositiveandnegativewaveformsindividually.D.16X2LCDDisplayInordertodisplaythemeasuredquantities,a16x2LCDdisplayisusedinthisprototype.VDDandVSSterminalsareusedtopowerdisplay.VEEterminalisusedforadjustingthecontrastofbackgreenlightinthedisplay.D1toD3bitsaregroundedandD4toD7bitsareusedasdatabitsfordisplay.RS,R/W,Earethecontrolpinstocontrolthedatai.e.toreadorwritefrommeasurementtodisplay.III.MEASUREMENTALGORITHMApartfromhardwarecircuitry,thereshouldbeasoftwaresupportasapartofcodinginordertomeasurepowerqualityparameters.Thiscodinghelpsinconnectingthehardwarecircuitstodigitalprocessorfordeliveringmeasuredparameters.Sointhissectioneveryparametermeasurementalgorithmisdiscussedwhichenablestoknowsoftwareprogramminginthemicrocontroller.Thealgorithmsfordifferentmeasuredquantitiesareasfollows.1)VoltageandCurrent-RootMeanSquareValueMeasurement:AHallEffectVoltageTransducerhavingarangeof0-500VisusedtomeasurevoltageandaHallEffectcurrentTransducerhavingarangeof0-100Aisusedtomeasurecurrentinthisprototype.ThefunctiontofindRootMeanSquare(RMS)Valueisgiveninequation(1)ThefunctionYmaybeavoltageorcurrentwhoseRMSvalueistobefoundandxwillbethenumberofsamplesoveraperiodofonecyclespecificallytakenas128samples/cycle.ThealgorithmformeasuringRMSvalueisgiveninFig.9.2)ActivePower:SoftwarealgorithmiswritteninMSP430takingtheoutputsofvoltageandcurrentsensorsthroughADC.ThefunctiontofindRootMeanSquare(RMS)Valueforpowerisgiveninequation(2).Theobjectiveofthealgorithmistocalculatethevaluesofpowerbymultiplyingvoltageandcurrentateachandeverysampleofthecyclewhichisillustratedinfig.10.Thiswillgivetheactivepowermeasurement.3)Frequency,PhaseAngleandPowerFactor:Frequencyofthesupplywaveformcanbedeterminedbyreciprocalofthetimeperiodbetweenzerocrossingsandthefunctiontofindfrequencyisgivenineqation(3).Frequency(F)=1/Timeperiod(T)-(3)Phaseanglecanbefoundfromzerocrossingsofthevoltageandcurrentwaveformsatsameinstantoftime.Thedifferencebetweenthezerocrossingswillgivesthephaseangleintermsoftimeanditcanbeconvertedintophaseanglebyequation(4).Phaseangle(PA)=TimeDifference*360/TimePeriod-(4).Powerfactorcanbedeterminedbytakingthecosineoftheanglebetweenvoltageandcurrent.i.e.phaseangle.Theexpressionforphaseangleisgiveninequation(5)PowerFactor(P.F)=Cos(phaseangle)(5)TherelatedsoftwarealgorithmforfindingthesethreeparametersisshowninFig.11.Italsoconsistsofaseparatealgorithmtodenoteleadingaswellaslaggingpowerfactors.4)Harmonics(TotalHarmonicDistortion):Harmonicsarethefrequenciesotherthanthefundamentalfrequency.Usuallytheyaremultiplesoffundamentalfrequency.Theycausedisturbancesinthepowersupplywhichwillproduceheat,noise.,etc.andalsoleadtonon-sinusoidalwaveformswhichmaydamagetheelectricalequipment.Tofindoutthem,amathematicalapproachFastFourierTransform(FFT)Analysisisusedwhichwillgivestheindividualharmonicsaswellastotalharmonicdistortion(THD).ThecalculationofharmoniccomponentsinananalogvoltageorcurrentwaveformisillustratedinFig.12.Initially,thesignalfromthevoltageorcurrenttransduceroutputisgiventoanADCinwhichitsampledas128samplespercycleandthatsampleddataisusedinprocessingofFFTanalysistocalculateHarmonics.ThemainpurposeofFFTanalysisistoconverttimedomainsignalintofrequencydomainwhichisexpressedbyequation(6).WhereK=0,1,2,.N-1Wherenistimedomainordinalandkisfrequencydomainordinal.NumberofsamplesisrepresentedbyNwhichis128inthiscase.Afterconvertingintofrequencydomain,wewillgettheexpressionas.thenthemagnitudeandphaseoftheharmonicscanbefoundbyequation(7).Duringtheconversionoftimedomainsignalintofrequencydomain,itisinterestingtoknowthatevensamplesandoddsamplesareseparatelyprocessedandfinallycombinedasshowninFig.13.ThesoftwarealgorithmtoforFFTanalysisisimplementedasshowninFig.14.Initiallydataisgiveninbitreversalorderasshowninfig.13andthenprocessedforfirststage,inthatfirstgroupandfirstbutterfly.Aftercomputationofthatbutterfly,thenitwillcompletesremainingallotherbutterfliessituatedindifferentgroupsofdifferentstagesasperabovealgorithmandfinallygivesthevaluesofHarmonicsinfrequencydomain.Inthisproposedprototype,itiscapableofmeasuring1to63orderharmonicsalongwithtotalharmonicdistortion(THD).Thetotalharmonicdistortionisdefinedastheratioofthesumofthepowersofallarmoniccomponentstothepowerofthefundamentalfrequencyasgiveninequation(8).Itdenotesthecompleteharmonicdistortionpresentinthesignal.Regardingmeasurement,specificallythepercentageTHDofthevoltagewaveformonlyispresentedintheLCDdisplay.IV.PROTOTYPEDEVELOPMENTANDTESTINGTheabovediscussioninthesectionsIIandIIIdescribesaboutthehardwareandsoftwareprogrammingthathavebeenusedinthisprototype.Inthissection,theentireschematicoftheproposedworkwhichshowstheconnectionofallcomponentsasinFig.15anditsdescriptionarediscussedindetail.Infig.15,itisobservedthatasinglephasepowersupplyisconnectedthroughvoltageandcurrenttransducerstoaloadwhosepowerqualityparametersaretobefound.Loadmaybearesistive,inductive,capacitiveorcombinationsofany.Regulatedpowersupplyisprovidedinordertogenerate+12V,-12Vforbiasingtransducersand+5VforpoweringMSP430microcontroller,LCDdisplay.AsalreadydiscussedinsectionII,op-ampcircuitryisusedforthreepurposesnamelyzerocrossingdetection,signalstrengtheningandsignalinversion.ThesethreecircuitsarebuiltforbothvoltageandcurrentusingaQuadchannelLM324OP-AMP.TheinputsforallthesethreecircuitryaresamenamelyVmandImwhicharenothingbutoutputsofvoltageandcurrentsensors.Theoutputsofthenoninvertingbufferforvoltageandcurrentaregiventoport6.0and6.2,outputoftheinvertingbuffersaregiventoport6.1and6.3andoutputofthezerocrossingdetectorsaregiventoport1.0and2.2respectivelyReferringtothesectionIII,thedigitalprocessingisexplainedandafteritscompletion,themeasuredelectricalparametersaredisplayedontheLCDbyconnectingthedatabitsD4,D5,D6andD7totheports3.4to3.7.Measuredparameterswillrepeatforeverycyclecontinuously.Testingoftherealizedprototypewasconductedinthelaboratorywithavailablestandardinstrumentslikeammeter,voltmeter,wattmeter,powerfactormeteralongwithdigitalstorageoscilloscope(DSO)andpowerqualityanalyzer(CW240)anufacturedbyYokogawacompany.Fig.16representstheprototypewithexperimentalsetupinthelaboratoryfortestingitsresponse.Duringexperimentation,prototypeistestedwithdifferentloadslikeR,RL,RC,andRLC.Italsotestedwithanonlinearloadtakenasinverteroutput.ThefinalresultsandobservationswillbediscussedinsectionV.Forexperimentation,thevalueofloadsRistakenas100ohms,Las50mHandCas50uF.SpecificationsofProposedPrototype:V.RESULTSANDOBSERVATIONSReferringtosectionIV,thetestingonprototypewithdifferentloadsarecarriedoutandtheresultsareasfollows.Observations:a)Theprototyperesultsarecomparedwithstandardinstrumentsresultsandnoticedthat,itishavingfairaccuracyexceptincaseofpercentagetotalharmonicdistortion(THD)ofvoltage.SothecodewrittenforFFTanalysisisvalidatedwiththeMATLABandtheresultsofindividualharmonicsalongwithTHDfoundtobeexactlysame.Sotheerrorismerelyduetothenoiseatthesensoroutputwhichwasobservedinthedigitalstorageoscilloscope.b)Sincethesoftwareiswrittenconsideringzerocrossingdetectionofvoltageandcurrentwaves,thisprototypemeterisgivingerrorsinthemeasurementsforaPWMWaveform(whichhasmanyzerocrossingsinacycle).VI.CONCLUSIONTheproposedprototypeisdesignedandimplementedtomeasurebasicpowerqualityparametersinasinglephasepowersystemwithfairaccuracy.Thisprototypehasbeendevelopedsatisfactorilywiththelimitedinputsanditcanbemadeintoalowcostproductbyprovidingupgradedenvironmentinthebothsoftwareandhardwaresections.Itmakesthesenseofknowingelectricalsystembehavioragainststandardsandfurtherleadstotakemeasurestoimprovethesystemperformance.Itisabasicstepforadvancedsmartmetering.ByprovidingnoiseimmunecircuitsatsensoroutputandchoosingmodernlatestcontrollerslikeDSPorFPGA,itcanbemerelyagoodequipmenttoanalyzealltypesofpowerqualityissues.ThisprototypeisalsocapableofmeasuringpowerqualityparametersforaPulsewidthmodulated(PWM)waveformsbyreplacingzerocrossingdetectionschemewithPhaseLockedLoop(PLL)synchronization.Thisworkcanbefurtherextendedtomeasurethreephasequantitiesbyprovidingadditionalequipment.REFERENCES:1AlessandroFerrero,MassimoLazzaroni,andSimonaSalicone“ACalibrationProcedureforaDigitalInstrumentforElectricPowerQualityMeasurement”IEEETransactionsonInstrumentationandMeasurement,Vol.51,No.4,August2002.2LoredanaCristaldi,AlessandroFerrero“AMethodandRelatedDigitalInstrumentfortheMeasurementoftheElectricPowerQuality”IEEETransactionsonPowerDelivery,Vol.10,No.3,July1995.3TomasRadil,PedroM.Ramos,A.CruzSerra“single-phasepowerqualityanalyzerbasedonanewdetectionandclassificationalgorithm”XIXIMEKOWorldCongress,FundamentalandAppliedMetrology,September611,2009,Lisbon,Portugal.4I.Iljazi,L.Arsov,M.Cundeva-BlajerandA.Abazi“CalibrationofaVirtualInstrumentforPowerQualityMonitoring”InternationalConferenceonRenewableEnergiesandPowerQuality(ICREPQ12)SantiagodeCompostela(Spain),28thto30thMarch,2012.测量单相电能质量参数的数字表的设计和样机研制SriramKarakanaElectricalandElectronicsEngineeringGVPCollegeofEngineering(A)Visakhapatnam,AP,INageswaraRaoNamburiProfessor,ElectricalandElectronicsEngineeringGVPCollegeofEngineering(A)Visakhapatnam,AP,Indianageswara.namburigvpce.ac.in摘要:在电力系统中，由于非线性和变化负载的存在，对电能质量的测量变得越来越重要。本文提出了一种数字仪表，设计并实现硬件测量基本的单相电能质量参数如电压、电流、频率、相位、功率因数、功率和总谐波失真（THD）。本硬件电路设计的目的是对上述电能质量参数进行测量，提高系统的性能。该仪器的基本输入为电压和电流信号，由电压和电流霍尔传感器检测。微控制器开发板（MSP430混合信号处理器）发射台由德克萨斯仪器制造用于两信号的数字处理。所有软件相关程序是用C语言代码在MSP430内部编写。一个16x2字节的液晶显示器用于显示电能质量参数。硬件电路的测试是用标准仪表在实验室完成的。通过使用YOKOGAWA生产的钳式电能质量计cw240，电能质量参数测量设备的实验结果会被报告出来。关键字：电能质量；总谐波畸变；霍尔传感器；MSP430；cw240I.引言在现代电力系统中，输入到电网中的电能的扰动主要是连续电源中的电力电子变换器注入到电网的谐波造成的。因此，在使用前有必要对一个系统的电能质量参数进行测量。并且为了能够更好的提高系统的整体性能，需要对其电能质量参数进行测量。本文提出了一种数字仪表，设计并实现硬件测量基本的单相电能质量参数如电压、电流、频率、相位、功率因数、功率和总谐波失真（THD）。由于该仪表是专为一个单相电力系统设计的，因此一套电流和电压传感器是满足设计需求的。对于电压，lv-25p霍尔电压传感器可以满足0-500V的变化范围。对于电流的测量，la-100p霍尔电流传感器可以满足0-100A的测量范围。传感器的偏置电压+12V和-12V分别是由稳压器LM7812和LM7912给稳压电源提供。混合信号处理器（MSP430）发射台采用TI用于数字处理。算法方面采用计算均方根值（RMS）功能来分析谐波，并且相关程序由C语言编写到MSP430中。硬件方面采用一个简单的运放电路过零检测电路来测量频率，并以电压跟随器来加强信号的强度，通过整流电路将最后的信号传递给ADC采样。其中LM324为四通道运算放大器，用于整流和过零检测电路。1602液晶显示器用于显示电能质量参数。硬件电路与实验室中的标准表如电流表、电压表、功率表，功率因数表和电能质量流量计进行比对测试。所有的硬件都在实验环境中进行了测试并将测量数据进行记录和分析。II.硬件组成该数字仪器框图如图1所示。单相电力系统由线路（L）和中性（N）。方框图主要由四部分组成。他们是a)霍尔效应传感器。b)信号调理电路。c）数字处理unit-msp430发射台。d）1602液晶显示器。A霍尔效应传感器要测量各种电能质量参数，所需的基本输入是电压和电流。因此，为了测量电压和电流，霍尔电流电压传感器（换能器）制造的问题进行原型。这些传感器进行测试和校准与实验室设备。上面的图显示电压互感器由两个输入端（+HT，HT），三个输出端（+，-，M）和两个电阻（R1）每个输入和输出（RM）。输入端子（+HT，HT）连接线和一个单相电源为中性。输出端（+和-）被用来给换能器的功率。他们可以连接到12V或15V。剩余的输出端（M）通过一个电阻RM和接地在RM的电压降会从换能器输入衰减电压。电阻的计算如下。初级额定电流（IPN）=10mA。最大电压，可以通过传感器感应=500伏。输入电阻（R1）=50公斤50K欧姆，5W。次级额定电流（是）=25。定义的次级电压输出=0.5V输出电阻（RM）=0.5v/25ma=20ohms20,0.25w。图3。显示电流传感器由三个输出端子（+，-，M）和输出电阻（RM）。它由一个中空的结构，在该结构中，供电线为裸线。输出端子（+和-）是用于功率传感器。他们可以连接到12V或15V。剩余的输出端（M）通过一个电阻RM在RM的电压降会连接到地面的衰减电压与电流测量。电阻的计算如下。次级额定电流（是）=100mA。定义的次级输出电压为2V。输出电阻（RM）=2V/100mA=20ohms。B信号处理电路一般来说，如果一个模拟信号的目的是给一个数字处理器像ADC或微控制器，然后给它应该操纵以满足要求的下一阶段进一步处理。这被称为信号处理。运算放大器是常用的信号处理电路。该模块中，三种电路由运放电路建立。他们是：1）过零检测器。2）电压跟随器（缓冲区）。3）反相放大器。1）过零检测电路：该电路通过零检测电路来实现信号频率的测量。如图4所示。两个连续的过零点和他们之间的时间为信号周期的一半，用来计算信号的频率。2）电压跟随器（缓冲区）：该电路是用来满足ADC的要求模拟信号放大和防止第二电路加载第一个电路。由