PERFORMANCE EXPLORATION OF SINGLE PHASE DAB DC-DC CONVERTER UNDER LOAD VARIATION

PERFORMANCE EXPLORATION OF SINGLE PHASE DAB DC-DC CONVERTER UNDER LOAD VARIATION

1Research Scholar, EEE Department, OUCE, Osmania University, Hyderabad, India

2Professor, EEE Department, OUCE, Osmania University, Hyderabad, India

Abstract - This article presents the performance analysis of single phase Dual Active Bridge (DAB) DC-DC converter under load variation. Two of the most importantcontrolgoals for DAB DC-DC converters are to achieve a high efficiency and a quick dynamic response. This paper concentrated on the quick dynamic response of the DAB. The phase shift pulse width modulation (PWM) is adopted for the control of switches. The proposed configuration is verified in the Matlab Simulink environment. The performance parameter of load voltage and power is presented and analyzed. The projected configuration is presented with and without voltage controller. The proportional and integral (PI) controller is adopted as voltage controller in this paper.

Key Words: DAB, DC-DC converter, Phase shift PWM, Proportional and Integral Controller, IGBT, Dynamic response.

1. INTRODUCTION

Dual active bridge (DAB) DC-DC converters have many benefits,suchasbeingabletosendpowerinbothdirections, havingahighpowerdensity,makingzero-voltageswitching easy to set up, and being easy to access for cascading and parallelism. Asaconsequenceofthis,theseconvertersare utilised in a variety of applications, including distributed generating systems, DC-micro-grid systems, electric car chargingsystems,energystoragesystems,andapplications involving power electronic transformers in railway locomotives.

Jan Riedel, et al. [1] investigated using these angles to selectivelysuppressvariousdcbuscurrentharmonicsover theconverter'sworkingrangetoreducethesizeoftheDAB dcbusbridgecapacitors. HaochenShi,etal.[2]presenteda methodfordecreasingreactivepowerwhileutilisingthree levels of modulated phase-shift control. Their goal was to improve efficiency in an extensive operation setting. JianqiangLiu,etal.[3]proposedapowerelectronictraction transformer (PETT) voltage balancing control approach using dual active bridge (DAB). Wensheng Song et al. [4] suggestedavirtualdirectpowercontrol(VDPC)strategyfor DABdc–dcconvertersthatusessingle-phase-shiftcontrolin ordertodealwiththeextremesituations Anaccurateand general model was presented by Anping Tong et al. [5] to characterisetheanalyticexpressionsoftheDABconverter

whileitwasunderthedirectionofTPS.Onthebasisofthis,a discussionoftheDABconverter'ssixdifferentoperational modeswillfollow. Inordertoimprovethepowerqualityof thegrid,AllanTayloretal.,[6]presentedamultiple-phaseshift control that makes it possible to implement a fixedswitching-frequencytriple-phaseshift(TPS)controlatthe lightload.Thiscontrolwouldbeusedatthelightload.The dynamic behaviour of a dual active-bridge (DAB) is discussedinKazutoTakagi'setal.'s[7]researchpaper.Jacob A. Mueller et. al., [8] offered a suggestion for generalized averagemodelsofdualactivebridge(DAB)converters.The useofgeneralizedaveragemodelingnecessitatesmakinga compromise between the model's accuracy and its tractability. TheauthorsNieHOUet.al.[9]proposedanew hybrid control method that they called EPS-DPC. This technique is a combination of EPS-DPC. EPS-DPC control possesses notable characteristics, not only in terms of its efficiencybutalsoofitsdynamicperformance.Acomplete optimizationcontrolapproachwaspresentedbyHouetal. [10] in order to increase the efficiency and dynamic response. Despite the widespread usage of this control method, however, the dynamic performance of the convertersstillhastobeimproved.Auniquetopologyfora dc power electronic transformer (DCPET) is proposed by JiepinZhangetal.intheirpaper[11],whichisintendedfor locomotives, ac/dc hybrid grids and dc distribution grids. The work of Shuai Shao and colleagues [12] presents a transformation in which distinct DAB working scenarios (forward/backward, buck/boost) might be comparable to oneanother.Asaresult,optimisationofonlyonescenario (forward/buck) is required to be performed. A unique neutral point clamped as DAB converter with a blocking capacitorwaspresentedbyYangXuanetal.[13]forusewith ESSindcmicro-grids. Ablockingcapacitorintheprimary loop of a conventional NPC DAB converter can match the transformer's primary and secondary winding voltage amplitudeswhenthevoltageratiois0.25,0.5,0.75,or1.A piecewisemodelofthemodulationmethodwascreatedby AmitKumarBhattacharjeeandcolleagues[14],whichpaves the way for analytical optimization. In addition, the optimization framework incorporates soft-switching conditions, which makes it possible to arrive at a comprehensive solution that lowers switching losses in addition to conduction losses. In conclusion, a hybrid controllerthatisbasedongeneralizedoptimizationhasbeen suggested as a solution. Alber Filba-Martinez, et al. [15]

developedasolutiontooperateMLIconverters.Thesolution was presented. The inherent imbalance of the voltages across the dc-link capacitors is the primary problem with these types of converters. This problem prevents the converterfromfunctioningcorrectlyandfrombeingutilized toitsfullpotential.M.A.Awal,alongwithotherresearchers, [16]suggestedamethodforbalancingthecapacitorvoltage

Atriplephaseshiftmodulation(TPS)withanoptimization techniquethat triesto maximize the efficiency ofthe dual activebridgeconverterwasproposedbySimonePistollato, etal.[17].Insmartdcpowersystems,sucha converter is frequently utilised to link renewable or energy storage systems. This is because loss minimization via TPS is essentialinthesetypesofsystems,particularlyinlight-load conditions. An enhanced model-based phase-shift control (MPSC) technique was proposed by Wenguang Zhao et al. [18]. Without having to make any adjustments to the controllerparameterswhiletheyarebeingusedonline,the improvedMPSCmethod.Theconstructionofthecontroller's parameters is straightforward, and the same model parameter has the same level of sensitivity as MPSC. Simulations and experiments have shown that it is useful and effective, proving its veracity. A deadbeat current controllerwaspresentedbyShushengWeietal.[19]foran isolated bidirectional DAB. A refined technique to single phase shift modulation is utilized by the controller in its operation.Thisisaccomplishedbyutilizingthepulsewidth as an additional control variable in addition to the phase shiftratio,whichistheonlycontrolvariableutilisedbythe standardsinglephaseshiftmodulation. KisuKimetal.[20] suggested a split-capacitor dual active-bridge (DAB) converter.SCstandsforsplitcapacitor.Todecreasethedcbiascurrentindual-active-bridge(DAB)converters,Qinglei Bu et al. [21] introduced a unique transient phase shift control (TPSC),whichisuniversal formultiplephaseshift control schemes.Tobegin,the dc-biascurrent modelsare constructed under a variety of distinct transient circumstances. Anoptimizedhybridmodulationsystemwas proposedbyLucasMondardoCnicoandcolleagues[22].This schemewasdevelopedtominimizethetotalpowerlossesof a 3-DAB converter when subjected to load and voltage changes.Afterreviewingliteraturesurvey,thesinglephase Full Bridge DAB is considered in this paper along with PS PWM due to its simplicity and easy to implement. The PI [23]-[28] controller is adopted in voltage control loop to control the voltage, current and power by controlling the dutycycle.

Thispaperisorganizedasfoursections.Thefirstsectionis theintroductionandliteraturesurvey.TheprinciplesofDAB are presented in section II. The performance parameters usingsimulationanalysisisdiscussedinsectionIII.Finally, theconclusionispresentedinsectionIV.

2. Dual Active Bridge DC-DC converter

The DAB consists of eight semiconductor devices, a high frequencytransformer,anenergytransferinductor,anddclinkcapacitors.Itisaregulated,bidirectional,high-powerdcdcconverter.Together,thesecomponentsmakeupthedual activebridge.Amoreeasyrepresentationoftheconverter canbemadebyimaginingitasastandardfull-bridgethathas beenfittedwitharegulatedrectifier.Thesymmetryofthis converter'sprimaryandsecondarybridgesmakesitpossible tocontrolthepassageofelectricityineitherdirection.Itwas chosenfortheapplicationinvolvingthesmartgreenpower nodeforthispurpose.Eachfull-bridgeconsistsoftwototempoledswitchingdevicesenergizedbycomplementarysquarewavepulses.Thesepulsesconstitutethedrivingforcebehind theoperationofthefull-bridge.Thesecomplementarypulses arewhatpowerthedevicesbeingdiscussedhere.Theterm "switching frequency" refers to the rate at which these complementarydevicesswitchonandoff.Thisfrequencyis used by the converter. IGBT components have been increasingly prevalent in the production of high voltage switching converters during the past few years. These deviceshavebeenusedtoproducetheseconvertersdespite not having an inherent body diode and having a bigger equivalent output capacitance than the devices that have beenusedpreviously.

Fig.1isa diagramthatillustratestheDABarchitecture.In thisdiagram,theletter'n'representstheturnsratioofthe transformer, v1 represents the output voltage of bridge 1, and v2 represents the output voltage of bridge 2. When combined, the two full-bridge circuits that make up the converter are connected to one another via an isolated transformerandanextrainductordenotedbytheletterLs. Theentirebridgeontheleft,whichislabelledasbridge1,is connectedtoahigh-voltageDCbus,whilstthebridgeonthe right,whichislabeledasbridge2,isconnectedtoanenergy storagedevice.Bothbridgesareshowninthefigurebelow. Theconverterissaidtobeoperatinginthe"forwardmode" when it is moving power from the DC bus into the energy storage device. When functioning in the reverse mode, electricityistransferredfromtheenergystoragesystemto theDCbus.Thisoccurswhenthesystemisinoperation.Asa consequenceofthis,powerdrawnfromthebatterywillbe depleted.

It is feasible to direct the flow of electricity over the dual active bridge by altering the phase of the pulses that are produced by one bridge in reference to the other. The control mechanism known as phase shift modulation, or morecommonlyabbreviatedasPS,reroutespowerbetween two dc buses in such a way that the leading bridge gives powertothetrailingbridge.Thisisaccomplishedbyshifting thephaseofthemodulationsignal.Sincethepowermaybe modifiedusingafundamentalPI-basedcontroller,thePhaseShift (PS) modulation is the method that can be put into practicewiththeleastamountofeffortandintheshortest amountoftime.Theswitchingcircuitisbuiltinsuchaway, ascanbeseeninFigures2and3,thatitgeneratesahighfrequency square-wave voltage with a duty cycle of fifty percent at each of the bridge terminals. This can be seen becausetheswitchingcircuitismadeinsuchaway.

Table -1: Specifications

Themodulationtechniqueknownas

islikelytheeasiestonetoimplementfortwinactivebridge converters. The degrees of freedom are reduced to ϕ as a resultoftheadoptionofD1=0.5andD2=0.5.

3. SIMULATION RESULT ANALYSIS

The proposed configuration is analyzed in two cases. The projectedworkispresentedwithoutusingvoltagecontroller in case1. In case 2, the voltage controller is added and presenteditsimpactontheoutputresults.Thesimulation specificationsarelistedinTable-1.

3.1 Without voltage controller

In this section, performance results of projected configurationarewithoutvoltagecontrollerispresented.

:Outputpowerunderloadvariation

Usinguncontrolledvoltageloopiscreatingthedistortionof outputsindynamiccondition.Inthisscenario,theresistive load of 46.3Ω is connected from t=0 sec to t=1 sec and anotherresistiveloadof40Ωisconnectedfromt=1secto t=2sec. The corresponding results are depicted in Fig. 4, Fig.5, Fig.6 and Fig.7. From Fig.4, it is observed that the transformersecondaryvoltageis230Vfrom0secto1sec anditisreducedto112att=1sec.Thetransformervoltage further reduced and reached to zero at t=2sec due to unavailability of voltage controller. Similarly, the load voltage,currentandpowerisalsoreachedzeroasdepicted inFig.5,Fig.6andFig.7.Hence,itisrequiredtoadoptvoltage controllertostabilizealltheseeffects

3.2 With voltage controller

In this section, performance results of projected configurationarewithvoltagecontrollerispresentedand analyzed.

:

Usingcontrolledvoltageloop,thecorrespondingresultsare depictedinFig.8,Fig.9,Fig.10andFig.11.FromFig.8,itis observedthat the transformersecondaryvoltageis230 V from0secto1secanditisreducedto112att=1sec.The transformer voltage of 112V is maintained constant after t=1secalsoduetoimpactofvoltagecontroller.Similarly,the loadvoltage,currentandpowerisalsocontrolledaftert=1 secasdepictedinFig.9,Fig.10andFig.11.Hence,itisproved thatthevoltagecontrolleriseffectivelyperformedforthis case.

The comparative performance analysis is illustrated in Fig.12, Fig.13 and Fig.14. From all these figures, it is observedthatthevoltagecontrolleriseffectivelyperformed indynamicconditions.

Fig -14:Outputpowerunderloadvariation

4. CONCLUSIONS

TheprincipleofsinglephaseDABispresented.Theconcept ofphaseshiftpulsewidthmodulationschemeisdescribed. The proposed configuration is analyzed in two cases including with and without voltage controller. The importanceofvoltagecontrollerisdescribedintheresults section.Theprojectedconfigurationissuffersfortheoutput parameters such as load voltage, load current and load power. These parameters are reaching zero during load variation. The above said problem is nullified using PI controllerwhichisadoptedinvoltagecontrollerblock.The PI is controller is effectively controlled the parameters of loadvoltage,loadcurrentandloadpower.

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BIOGRAPHIES

G. Jhansi Rani received B. Tech in Electrical and Electronics EngineeringfromJNTU,Hyderabad in 2007 and M. Tech in Power and Industrial Drives from JNTU, Anantapur in 2009. Currently working as an Assistant Professor (c) in Department of Electrical Engineering, University College of Engineering, Osmania University, Hyderabad,India.Researchinterests include various dc-dc power converters and power electronics applications, Multi-level inverters, Power conversion and energy managementforMicro-grids.

Prof. P. Srinivas graduated in Electrical&ElectronicsEngineering fromKakatiyaUniversity,Warangal in 1998 and received M. Tech. in Electrical Machines & Industrial Drives from National Institute of Technology, Warangal in 2000.Presently he is serving as Professor in the Department of Electrical Engineering, Osmania University. He completed Ph. D in the field of Switched Reluctance Motor Drives. His areas of interest are Special Electrical Machines, AI TechniquestoElectricDrives.