International Research Journal of Engineering and Technology (IRJET)e-ISSN: 2395 -0056 Volume: 02 Issue: 04 | July-2015 www.irjet.net p-ISSN: 2395-0072 2015, IRJET.NET- All Rights Reserved Page 1315 A Review of Cascaded H-Bridge Multilevel Inverter: Control Techniques and its applicationSourabh Rathore1, Mukesh Kumar Kirar2, S.K.Bharadwaj3 1 M.Tech Scholar, Electrical Engineering, MANIT Bhopal, Madhya Pradesh, India 2 Assistant Professor, Electrical Engineering, MANIT Bhopal, Madhya Pradesh, India 3 Professor, Electrical Engineering, MANIT Bhopal, Madhya Pradesh, India ---------------------------------------------------------------------***---------------------------------------------------------------------Abstract-Multilevelinverters(MLI)haslargely attracted theattention ofacademic and industries. The demand of MLI has increased recently as it is capable of generatingqualitywaveformbyusinglowvoltage devices,reducedswitchingfrequenciesandreduced harmonicscontentoftheoutputpower.Thereare severaltopologiesdiscussedandanalyzedinliterature in past decades. In this paper, we have considered three topologies:Diodeclampedinverter(DC-MLI),flying capacitor(FC-MLI),cascadedH-Bridgeinverter(CHB-MLI).WehavetakenCHB-MLIasareferencefor explainingthreetechniques:phasedisposition(PD), phaseoppositiondisposition(POD),alternatephase oppositiondisposition(APOD).Afteranalyzingthese three techniques, we observed that PD is best technique asitgiveslesstotalharmonicdistortion(THD)content in voltage level. KeyWords:CascadeH-Bridge,Diodeclamped inverter, flying capacitor, and phase disposition. 1. INVERTER PowerelectronicinverterisadevicewhichconvertsDC electricalpowerstraightintoHVACelectricalpower. Throughoutconversion,theactualresultvoltageas,well asusuallyiskeptconstant.Thisistermedseries commutatedinverterswhilethatworksinsideinversion mode.CollectioncommittedinvertersinvolveHVACoffer inthecourseofconversionintheresultingterminal.[1], [2]Thismeansthatseriescommittedinverterscantbe the remote HVAC voltage places as well as being a variable regularityturbinesalongwithDCelectricalpowerinthe suggestions.Forthatreason,voltagedegree,regularityas wellaswaveformwithintheHVACaspectintheseries committed inverters cant always be changed. The actual HVAC result voltage supply along with variable voltageworthaswellasregularityworthsothatyoucan havegotawiderangeofapplication.Invertersmightbe labeledstraightintoacouplekindsdependingontheir particular function [3]-[5]: Voltage Source Inverters (VSI) Current Source Inverters (CSI) Square wave Modified sqaure waveMultilevelSine wave2-level 3-level 7-level Fig- 1: Inverter output waveforms Nowwearegoingtoclassifymultilevelconverterinto current source inverter, voltage source inverter. MULTILEVEL INVERTERSLOAD COMMUTATED CURRENT SOURCE INVERTER2 LEVEL VOLTAGE SOURCE MULTIPLE DC SOURCECSEQUAL DC SOURCESCASCADED H- BRODGESINGLE DC SOURCESFLYING CAPACITORUNEQUAL DC SOURCESDC-AC POWER CONVERSIONCURRENT SOURCEVOLTAGE SOURCEDIODE CLAMPED Fig-2:Classification of Multilevel converter International Research Journal of Engineering and Technology (IRJET)e-ISSN: 2395 -0056 Volume: 02 Issue: 04 | July-2015 www.irjet.net p-ISSN: 2395-0072 2015, IRJET.NET- All Rights Reserved Page 1316 1.1 Multilevel Inverters

Themultilevelinverterincludesavarietyofenergy semiconductorgadgetsandalsocapacitivevoltage sources.Theparticularmovedwaveformconnectedwith outputvoltagecanbecreated[6],[7].Theparticular commutationinthechangeswillallowtheparticular supplementinthecapacitorvoltagestoobtainhigh- voltage at the output, as the energy semiconductors ought towithstandmerelylessenedvoltages.Theparticular generalized moved waveform to get a single-phase N-level multilevelinvertercanberevealedthroughoutFig.3The particularwaveformiscomposedofidenticaloptimistic andalsobadhalvesconnectedwith(N-1)/2voltage amounts where the sine wavemay be approximated since revealed. tVo(N-1)/201 2n-(N-1)/2-Vdc-VdcVdc2Vdc Fig-3.:Generalizedsteppedwaveformofmultilevel inverters 1)Diode-Clamped Multilevel Inverter (DC-MLI) Thediode-clampedmultilevelinverteristhenamegiven toneutral-pointclampedPWMinverterextendedtoa highernumberoflevels[8].Thediode-clampedmultilevel inverterhasfoundwideacceptanceforitscapabilityof highvoltageandhigh-efficiencyoperation.Thepower ratingoftheconvertercanbedoubled.Inadditiontothis theneutralpointenablesthegenerationofazerovoltage level,obtainingoverallthreedifferentvoltagelevels[9]-[12]. VdcC1C2Vdc/2Vdc/2S1S2S1'S2'D1D2A N Fig-4 :A 3-level Diode-clamped inverter Table-1:SwitchingPatternofDiode-ClampedMultilevel Inverter Table-1presentsswitchingpatternofa3-leveldiode-clamped inverter. State 1 indicates that the switch is ON and state 0 indicates that the switch is OFF. It is obvious from this table that in each cycle just four switches should beON.Itisevidentfromthetablethatadiode-clamped multilevel inverter does not possess phase redundancies. 2)Flying-Capacitor Multilevel Inverter (FC-MLI) Figure2.5showsonephaselegofthepowercircuitfora flying-capacitor3-levelinverter.TheFC-MLItopologyis somewhatsimilartoDC-MLIwhileusingthemajor differencebecomingtheclampingdiodesaregenerally replacedthroughFC-MLI[62],sinceissovisiblewithin Fig. 5 Any. Below the stress cant become directly linked to producethisabsolutelynothingvoltagestage.Asan alternative,thisabsolutelynothingstagecanbereceived throughjoiningthestressonthebeneficialormaybe adversebarfromtheFC-MLItogetherwithopposite polarity based on the dc-link. Like with this DC-MLI, a just pairofgatingsignsisessentialforeachperiodtoprevent dcwebsitelinkandalsoFC-MLIshort-circuit.Adifferent differencewhileusingtheNPCcanbetheseveral combiningofSw1;Sw2aregenerallypermitted.The middlecircuittogetherwithswitch(Sw1;Sw2)=(1,0) whichoftenyieldsthisabsolutelynothingstage.Identical stagecanbereceivedtogetherwith(Sw1;Sw2)=(0,1). Thatpropertyorhomeistermedvoltagestage redundancy and also can be used with regard to control or maybe optimization uses [12]-[15]. Output voltage Vo=Van Switch states S1S2S1S2 Vdc/21100 00110 -Vdc/20011 International Research Journal of Engineering and Technology (IRJET)e-ISSN: 2395 -0056 Volume: 02 Issue: 04 | July-2015 www.irjet.net p-ISSN: 2395-0072 2015, IRJET.NET- All Rights Reserved Page 1317 VdcVdcS1S2S1'S2'C2VdcA N Fig-5:A 3-level flying capacitor inverter Table-2:SwitchingPatternofFlying-CapacitorMultilevel Inverter Asevidentfromtable2.4,FC-MLImultilevelinverter possesses phase redundancies. These redundancies can be incorporatedinthecontrolstrategywhichultimately helpsinregulatingthevoltageacrossthedc-link capacitors. The main advantages and disadvantages of FC-MLI multilevel inverter are listed below [16]. 3) Cascaded H-Bridge Multilevel Inverter (CHB-MLI) CHB-MLIisformedbytheseriesconnectionoftwoor moresingle-phaseH-bridgeinverters;hencethenameH-bridgeisgiven[17].EachH-bridgecorrespondstotwo voltagesourcephaselegs,wherethelinelinevoltageis theinverteroutputvoltage.Therefore,threedifferent voltagelevelsaregeneratedusingasingleH-bridge converter.AndseriesconnectionofNsuchbridgescan produce2N+1levelsintheoutput.Thisseriesconnection istermedascascadedH-bridgemultilevelinverter[18]. Each leg has only two possible switching states, toneglect dc-linkcapacitorshort-circuit.Sincetherearetwolegs, fourdifferentswitchingstatesarepossible,althoughtwo of them have redundant output voltage. S4 S3S2VoS1Vdc Fig-6:A 3-Level Cascaded H-Bridge Inverter Table-3:SwitchingPatternofCascadedH-Capacitor Multilevel Inverter ThefunctioningofasingleH-bridgeissimilartothatof conventional2-levelinverter.EachH-bridgerequiresan isolated dc source/capacitor to generate its corresponding output.Theswitchesareactivatedinsuchawaythatthe output voltage across the load terminals is the aggregation ofthevoltagegeneratedbyalltheH-bridges.The switchingpatternfora3-levelinverterisshownintable 2.4.2 MODULATION TECHNIQUES Importantly thepowerelectronic converters are operated in the switched mode.The switches of the converter are alwaysineitheroneofthetwostates-OFF(nocurrent flows),orON(saturatedwithonlyasmallvoltagedrop acrosstheswitch).[19-21].theswitchedcomponentis Output voltage Vo=Van Switch states S1S2S1S2 Vdc1100 01010 -Vdc0101 0011 Output voltage Vo=Van Switch states S1S2S1S2 Vdc1101 01000 -Vdc0111 0010 International Research Journal of Engineering and Technology (IRJET)e-ISSN: 2395 -0056 Volume: 02 Issue: 04 | July-2015 www.irjet.net p-ISSN: 2395-0072 2015, IRJET.NET- All Rights Reserved Page 1318 attenuatedandthedesiredDCorlowfrequencyAC componentisachieved.ThatiscalledPulseWidth Modulation(PWM),sincethedesiredaveragevalueis controlled by modulating the width of the pulses [22]-[26]. Multicarrier PWMSpace Vector ModulationHybrid ModulationMultilevel ModulationLow Switching FrequencyHigh Switching FrequencyPhase ShiftedLevel ShiftedPD-PWMPOD-PWMAPOD-PWMFig-7: Classification of multilevel modulation methods 2.1 Multicarrier PWM Multicarrier PWM is used when deals three level or higher levelsininverteroutput.MultilevelPWMisbasicallya generalizationofthe2-levelPWMwhereinthesinusoidal referencesignalisnaturallysampledwiththehelpofa numberofcarriersignals[27.]Tobemorespecific,anN-levelmultilevelinverterrequiresN-1carriersignalsto samplethereferencesignalandgeneratetheswitching signalsforthepowerswitchesincorporatedinthe inverter topology [28]. 2.1.1 Level Shifted PWM (LS-PWM) Itisthemostimportantfileformatonthe2-levelPWM withregardtoN-levelmultilevelinverterwheninsteadof just one provider signal, N-1 provider alerts are employed which are moved vertically withrespectto the other [28]. Due to the fact just about every provider is usually related totwoamountsPWM,theidenticalbasicprinciplecanbe employed,usingthatthiscommandsignalneedstobe aimedtowardscorrectpowerturnssothatyoucanmake this related amounts within the end result [29]-[31]. PhaseDisposition(PD-PWM):whereinallthe carrier signals are in same phase. PhaseOppositionDisposition(POD-PWM): wherein the carrier signals above the zero are out of phase with those below the zero by 180. AlternativePhaseoppositionDisposition (APOD-PWM):whereintheadjacentcarrier signals are out of phase by 180. Table-4: Comparisons of Three Topologies TopologiesMeritsDemerits 1.Diode Clamped Controlmethodis simple. Inverterefficiencyis high. Morenumber ofclamping diodesis requiredwhen thenumberof levels is high. 2.Flying Capacitor Both real and reactive powerflowcanbe controlled. Inverter control canbevery complicated whenthenoof levels is high. 3.CascadeH-Bridge Comparedwiththe NPCandFCinverters itrequirestheleast numberof componentsto achievethesame numberofvoltage levels. Itneeds separatedc sourcesforreal power conversions, thereby limitingits applications 3. CONCLUSIONS Inthispapertherearethreetopologies:Diodeclamped inverter,flyingcapacitorinverter,CascadeH-bridge inverterwhichhavebeendiscussedandanalyzed consideringallparametersandconditions.Wehave mentionedmodulationtechniquesbriefly.Andthe invertertopologiesarethencomparedonthebasisof International Research Journal of Engineering and Technology (IRJET)e-ISSN: 2395 -0056 Volume: 02 Issue: 04 | July-2015 www.irjet.net p-ISSN: 2395-0072 2015, IRJET.NET- All Rights Reserved Page 1319 modulation techniques. The three technique of modulation Classifiedas:Phasedisposition,Phaseopposition dispositionandAlternatePhaseoppositionarediscussed consideringallparameters.PDgivesbetterresult compared to POD, and APOD techniques. REFERENCES [1].H.Stemmler."Powerelectronicsinelectrictraction applicationsIEEEconferenceofIndustrialElectronics, Control and Instrumentation," IECON93, 1993 [2].H.Fujita,S.Tominaga,andH.Akagi."Analysisand designofanadvancedstaticVARcompensatorusingquad-seriesvoltage-sourceinverters.IEEEIndustryApps Meeting, 3:25652572, 1995 [3].Y.Yoshioka,S.Konishi,N.Eguchi,M.Yamamoto,K. Endo,K.Maruyama,andK.Hino."Self-commutatedstatic flickercompensatorforarcfurnaces.InIEEEApplied Power Electronics Conference, volume 2, , 1996. [4]. L L. Gyugyi, "Power electronics in electric utilities: static var compensators.," Proc. IEEE, vol.76,, 1987. [5].PeterW.Hammond."Anewapproachtoenhance powerqualityformediumvoltageACdrives.IEEETrans. Industry Applications, 33(1):202208, January 1997. [6]L. M. 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[27]JagdishKumar,BiswarupDas,andPramodAgarwal, SelectiveHarmonicEliminationtechniqueforaMultilevel inverter,inProc.of15thNationalPowerSystems Conference (NPSC), IIT Bombay, [28]BurakOzpineci,LeonM.Tolbert,JohnN.Chiasson, HarmonicOptimisationofMultilevelConvertersusing Genetic Algorithms, IEEE Power Electronics Letters, vol. 3, no. 3. [29]S.K.Pillai,Afirstcourseonelectricaldrives,2nd ed., New Age International Publishers, 2004. [30]P. D.Ziogas.Thedeltamodulationtechniqueinstatic PWMinverters.IEEETransIndustrialApplications,IA-17(2):199204, March 1981. [31] Gupta, K.K.; Jain, S.; , "Topology for multilevel inverters to attain maximum number of levels from given DC sources," Power Electronics, IET , vol.5, no.4, pp.435-446, April 2012. BIOGRAPHIES SourabhRathorehasreceivedBE (Electrical)degreeFromSagar InstituteResearchTechnology andScienceBhopalin2012and pursuinghisM.Techdegreein PowerSystemfromMANIT Bhopal. Mukesh Kumar Kirar received the BE(Electrical)degreefrom GovernmentEngg.College,Ujjain India in 2006 and M.Tech (Power System)in2008fromMANIT BhopalandPhDin2014from MANITBhopal.Heiscurrently working as an assistant professor IntheDepartmentofElectrical Engineering,MANIT,Bhopal, India.HisfieldofInterestsis powersystemstabilityand control,transformerand machines.S.K.BharadwajreceivedtheBE (Electrical)degreefromI.T.B.H.U. VaranasiIndiaIn1975and M.Tech(PowerSystem)in1978 fromRECKurukshetra.andPhD (ApplicationofselfTuning StrategiestoelectricDrive)in 2000fromBarkatullah University.Heiscurrently workingasaprofessorinthe DepartmentofElectrical Engineering,MANIT,andBhopal, India.Hehas9researchpapers inNationalConferenceand7 researchpapersinInternational ConferenceHisfieldofInterest arepowersystemandenergy conservation.