PWM外文文献

NetworkandComplexSystems(Paper)ISSN2225-0603(Online)Vol.5,No.3,20151AchievingaSinglePhasePWMInverterusing3525APWMICOmokereE.SNwokoye,A.O.CDepartmentofPhysicsandIndustrialPhysicsNnamdiAzikiweUniversity,Awka,AnambraState,NigeriaAbstractThispaperpresentsthedevelopmentofcontrolcircuitforsinglephaseinverterusingapulsewidthmodulation(PWM)IC.Theattractivenessofthisconfigurationistheeliminationofacomplexcircuitrytogenerateoscillationpulsesfortransistorswitches.The3525Acontrollerisabletogeneratethenecessarywaveformstocontrolthefrequencyoftheinverterthroughproperuseofswitchingpulse.TheDCtoACinversionwassuccessfullyachievedalongsidetheswitchingsignals;thecontrollerproducedinverteroutputoffrequencynearly50Hz.1.IntroductionPulsewidthmodulation(PWM)isawayofdigitallyencodinganalogsignallevels.Itisatechniquethatisnowgraduallytakingovertheinvertermarketofcontrolapplication.Thetechniquecombinesbothfrequencyandvoltagecontrol(JameerbacusandSoyjaudah,2000;NPTEL,2007;IslamandShari,2009;Vodovozov,2010).ThePWMcircuitgivesachainofconstantamplitudepulsesinwhichthepulsedurationismodulatedtoobtainthenecessaryspecificwaveformontheconstantpulsingperiod.InPWM,thecontrolledoutputvoltageiseasilyobtainedbyswitchingthetransistorsONandOFFmanytimeswithinacycletogenerateavariablevoltageoutputwhichisnormallylowinharmoniccontent(JameerbacusandSoyjaudah,2000;Bose,2006;Vodovozov2010).TheperformanceofaPWMconvertersignificantlydependsonthecontrolmethodandthetypeofmodulation.Pulsewidthmodulatorsarenowavailableinavarietyofdesignsandintegratedcircuits,whichgreatlysimplifiesthedesignandimplementation.Toachievethecontrolsystem,the3525APWMICwasused,anditbringssimplicitywithitslowcostimplementationandhasasmallsizeofcontrolcircuitforthesinglephasebridgeinverter.2.TheSinglePhaseFullBridgeInverterTheinverter,alsoknownasDCtoACconverterconvertsdcpowertoacpoweratdesiredoutputvoltageandfrequency.Theoutputvoltageofaninverterhasaperiodicwaveformthatisnotsinusoidalbutcanbemadetocloselyapproximatethisdesirewaveform.Itisanelectronicpowerconverterthatisnecessaryasaninterfacebetweenthepowerinputandtheload(Salam,2002;Bose,2006;Vodovozov,2010;SenthikumarandSingaaravelu,2010).Thefullbridge(singlephase)inverterisbuiltfromtwohalfbridgesconnectedtoformwhatisknownasafullbridgeorH-bridgeinverter.Itsarrangementisshowninfigure2.ItcomprisesofDCvoltagesource,4powerswitches(usuallybipolarjunctiontransistors-BJTs,metal-oxidesemiconductorfieldeffecttransistors-MOSFETs,insulatedgatebipolartransistors-IGBTsorgateturnedontransistors-GTOs)andtheload(Bose,2006;SenthikumarandSingaaravelu,2010;Harifetal,2011).Figure1:Fullbridgesinglephaseinverter[CurledfromBoseB.K.2006]Tocreateasquare-waveoutputvoltage,thedevicepairsQ1Q3andQ2Q4areswitchedalternativelyatadelayofShanxiUniversity(218.26.34.64)-2016/5/18DownloadNetworkandComplexSystems(Paper)ISSN2225-0603(Online)Vol.5,No.3,20152180degrees.WhenQ1andQ3areONwithQ2Q4OFFforadurationt,alsowithQ2Q4ONandQ1Q3OFFatt.Assumingthereisasinusoidalloadcurrent,theloadwillabsorbpowerwhenQ1Q3andQ2Q4pairsareconductingalternativelywhereasfeedbackingoccurswhenthediodepairsareconducting(Salam,2002;Bose,2006;NPTEL,2007).Foracompleteoperationintime,theoutputisasshowninfigure2.Figure2:Loadvoltageandcurrentwaveinfullbridge[CurledfromBoseB.K.2006]Amethodofcontrollingtheoutputvoltageoftheinverterinfigure2calledphaseshiftcontrol(alsocalledphaseshiftpulsewidthmodulation)isshowninfigure3.Figure3:Phaseshiftvoltagecontrol[CurledfromBoseB.K.2006]Here,bothhalf-bridgesoftheinverteraremadetooperateinsquare-wavemode,buttherightsidehalfbridgeoperatesataphaseshiftangleφasshowninthefigure.TheoutputvoltageVab=Vao–Vbo.Toachieveahighpracticalsinusoidaloutput,alowpassfilterisconnectedattheinverteroutputterminalstominimisehighfrequencyharmonicsdistortionthatisfoundinthesquarewaveoutput(JahmeerbacusandSoyjaudah,2000a,b;Salam,2002).TheswitchingONandOFFoperationbytheswitchesiscontrolledbycontrolcircuitry.ShanxiUniversity(218.26.34.64)-2016/5/18DownloadNetworkandComplexSystems(Paper)ISSN2225-0603(Online)Vol.5,No.3,201533.ApproachandMethodFigure4istheblockdiagramthatdescribesthehardwaredevelopmentforcontrollercircuitcombinedwiththeinverterswitches.Thearrowshowsthesignalflowthroughtheinvertertotheload.Figure4:SignalflowofInverterhardwareTheswitchingfrequencyusedinthisprojectis50Hz.Itisdesiredtocontroltheinverterwithproperswitchingsignals.TheturnonandturnofftimeoftheswitchesisdeterminedbythisPWMcontrolsignalgeneratedbythe3525AICcontroller.Beforethiscontrolsignalisbeinggenerated,propercalculationisdonetodeterminethesuitableswitchingpulsesconditions(frequency)fortheswitches(STMicroelectronics,2011).Figure5showstheapproachinwhichthecontrolleroutputsareconnectedwiththeinverterMOSFETswitchesasusedinthiswork.TheturnONandOFFforQ1andQ3arecontrolledbyPWMAgeneratedatpin11.WhiletheturnONandOFFforQ2andQ4arecontrolledbyPWMBgeneratedatpin14.BothPWMAandPWMBusedthesamecontrolsignalgeneratedbytheIC.WithPWMAsignalleadingPWMBbyhalfcycleor180