maximum power point technique (mppt) for pv system based ... · power point) control algorithm to...

InternationalResearchJournalofEngineeringandTechnology(IRJET)e-ISSN:2395-0056Volume:06Issue:12|Dec2019www.irjet.net p-ISSN:2395-0072

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MaximumPowerPointTechnique(MPPT)forPVSystemBasedonImprovedPertandObserve(P&O)MethodwithPIController

KifayatUllah*1,Dr.YajunWang2,AsimZaman2,H.HasnainImtiaz2,Safiyo.M.Ahmad2,BheeshamKumar3,

1,2,SchoolofElectronicsandInformation,LiaoningUniversityofTechnology,Jinzhou,P.RChina3,DepartmentofElectricalandElectronics,NorthChinaElectricPowerUniversity,Beijing,P.RChina

---------------------------------------------------------------------***---------------------------------------------------------------------Abstract-Photovoltaicpowergenerationsystemhaskeyruleinelectricityproduction.Although,itiscleanrenewableenergywithunlimitedresourcesbutithassomedrawbacksin efficiency. In order tomaximize the efficiency, PV arraymust drive at maximum power point. For the reason so,severalalgorithmsareusedinPVsystemtotrackMPPandreduce the operational losses. The pert and observe P&Oalgorithm ismost commonly used because of its simplicityand low cost. Though it is easy to install, but it has rippledrawbackwhen it reaches toMPP. In this paper improvedpertandobserveP&OMPPTcontroltechniqueisintroducedby the addition of PI controller to the algorithm. In thismethod ripple aroundmaximumpowerpoint are removedunderstableexternalenvironmentandunstablecondition.Atthe end simulation is performed. Simulation results showsthat the improvedmethodMPP tacking effect is improvedandtheefficiencyisalsoslightlyincreased.KeyWords:Photovoltaicsystem,MPPTtechniques,MATLAB,Renewableenergy,Boostconverter1.INTRODUCTIONBecause of the limited conventional fossil resources forproduction of electrical energy and growing globalpopulation the demand of electricity is increasingaccordingly.Tomeetingtheriseinelectricitydemand,thepower production companies are looking forunconventional resources. In theworld today, renewableenergy is the only replacement, not only to fulfil powerrequirement,butalsocanreducedthecarbonsubstancesintheair.Solarpowergenerationeffectcanbeconsideredthehighest suitable among the renewable energy resources,because of the cleanest, unlimited amount, andsustainabilityofsolarenergy[1].

The basic operation of photovoltaic power system is thedirect conversion of sun light into electrical energy bymeansofsemiconductordevices[2].TheproductivityofPVarraydependson theexternalenvironment temperature,solarirradiance,andoutputvoltageofPVunit[3].BecauseofnonlinearcharacteristicsofPVarray, it is importanttousepowerelectronicsdevicesalongwithMPP(maximumpowerpoint)controlalgorithmtomaximizetheefficiencyofphotovoltaicarray.ToachievemaximumpoweroutputfromaPVarraycanbedonebyMPPT(maximumpower

point technique) controller [4] [5]. A PV array produceslesser power, so the duty of a MPPT in a PV powertransformationsystemistoconstantlyadjustthesystemsothatitcangetfullpowerfromthePVarrayunderdifferentweatherandloadconditions[6].NumerousMPPTcontroltechniques are established to track the MPP (maximumpower point) efficiently. Most of the conventional MPPTtechniqueshasdrawbackofbeingslowtrackingMPP,thereason so, the efficiency of PV system is reduced. Inliterature [7] [8] [9] they are largely classified into twokinds, specifically the soft computing and conventionalapproach. Most often use conventional MPPT are the IC(incremental conductance) [10], P&O (perturbation andobservation and hill climbing method [11]. These MPPTcontrol algorithms are commonly used because of theirsimplicity and strength. Moreover, soft computingMPPTtechniques such as fuzzy logic [12], artificial neuralnetwork , differential evolution and particle swarmoptimization [13] aremore flexible andadaptable.TheseMPPT has improved steady state performance, but thesearesignificantlyslowandcostly. In the traditionalMPPT,P&Oisthesimpleanddemonstratesverygood.However,thistechniquesuffersfromtwosoberweaknesses.OnebigproblemisthenonstoposcillationthatappearsacrosstheMPP.Secondisslowtrackingwhenwhetherchangerapidly[14].Inaddition,Becauseoftheclosedlooptrackingofsunlight,theoutputoftheMPPTcontrollercontainsharmonics,whichcanbeminimizedbyusingfiltercircuit.Duetothesmall output voltage of PV array, a non-isolated DC-DCconverter is used for providing maximum power to theload.ADCtoDCconverterworkasaninterfacebetweentheloadandPVarray.ThemostcommonlyboostconverterisuseinPVsystemasmaincircuitduetoitsadvantages[15].

2.PHOTOVOLTAICSYSTEMBasically,aphotovoltaicpowergenerationsystem issolidstatesemiconductordevice,whenitisvisibletothesunlightit produces electrical energy. Combination of many solarcellsindifferentconnectionisbasicallycalledphotovoltaicpanel. A photovoltaic module is made by linking severalsolar cells together in parallel and series. To achievingmaximumoutput current, PV cells are coupled inparalleland for getting maximum output voltage PV cells areconnectedinseries[16].



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Photovoltaicpowergenerationsystemconsistsonseveralcomponents such as photovoltaic array,DC-DC converter,MPPTcontrolunit,batterystorageandinverteretc.whichareshowninfigure1.

Fig-1:BasicstructurediagramofPVsystem

When PV array generates electricity, the duty of MPPTcontrolleristocalculatethereferencevoltageandfindtheMPP (maximumpower point). DC-DC converter basicallyperformworkasmediator,whichtransfervoltagefromPVtotheload[17].Batterystorageisprovidingelectricitytotheoutputloadduringatnighttimeorrainyweatherwhenlight intensity is entirely low. This only compatible withstandardalonePVsystem.WhiletheinvertercircuitisusestofeedACoutputvoltage[18].

Photovoltaicgenerationsystemsaregenerallycategorizedon thebasisof their functionalityandoperatingsystems,element alignments, and the electrical load. Such asstandalone and grid connected structures which areproposedtoprovidespowertotheloadandenergystoragesystems. The standalone system is proposed to workindividuallyoftheutilitygridandsupplytocertainload.Ontheotherhand,grid connectedPVsystem isproposed towork in parallel connection and connected with theelectricalgridsystem.ThemostlyconsistonDC-ACinverterwhichconvertDCoutputofthePVarray[19].BesidethisPVsystemhasonemoretypecalledhybridsystem,whichmostlycombinedwithwindturbineordieselgenerator.

2.MODELINGANDSIMULATIONOFPVSYSTEM

Fig-2:simulationmodelofPVsystem

2.1PVCellThevoltageofphotovoltaiccellisabout0.4Vto0.5Vand

theworkingcurrentisabout25mA/cm2.Forthereasonso,thesecellsarecombinedtogetherthatmeetneedsofoutputload. As the sun light strokes on PV cells, it acts like aforwarddiodeonabigsurface[20].

EquivalentcircuitofPhotovoltaiccellisgiveninfigure3, where; I=output current; V=output voltage, Iph=opticalcurrentandIsh=leakagecurrentofthephotovoltaiccell.

Fig-3:Equivalentcircuitforphotovoltaiccells

Currentproducingincellduringlighthitting:

I=I!" − I% &exp *+(-./01)345

6 − 18 − -./01019

(1)

Where; k=Boltzmann’s constant, T=temperature,Rsh=parallelequivalentresistanceandRs=seriesequivalentresistance.

Simulation model of the photovoltaic array, outputpowercharacteristiccurvesandparameterstablearegivenas follow. One parallel and two series connected arraymoduleisusedinthesimulation.

Fig-4:simulationmodelofPVcell

Table -1: Detailed electrical parameters for Trina solarTSM-185DA01A.08

BatteryStorage

PhotovoltaicArray

MPPTController

DC-DCConverter

LoadDC-ACInverter

i+

-

Ipv

v+

-

Vo

+

Ipv

Vpv

g

MPPT

+

+

v+

-

Upv

Continuous

Ir

T

mm

+

-

i+

-

Ipv1

g

CE

+

Vpv

Ipv

PWM

duty cycle

MPPT1

Signal 2

Signal 1

Group 1

Irradiance

Signal 2Group 1

Temperature

Iph

VDID

Rsh Ish RL

RsI

V

Vd=V_PV + Rs*I_PV2-

1+

1m

2TempC

1S

v+-

V_PVIdio

de

AK

Diode Rsh

s -+

IL

i+ -

I_PV

+

Rs_array

Rs*Nser/Npar

Rs_array_

+

Rsh_arrayFor 0.05*Sref

{Vd}

Vd1

Temperature

Irradiance

IL

IL ctrl

in out

I Filter

in out

V Filter

V_PV

I_PV

I_PV

Vd

I_diode

Irradiance (W/m2)

Temperature (deg C)



815

Parameters Values

Maximumoutputpower(Pm) 185.554W

CurrentatMPP(Imp) 5.14A

Cellspermodule(Ncell) 72

Opencircuitvoltage(Voc) 44.65V

VoltageatMPP(Vmp) 36.1V

Short-circuitcurrent(Isc) 5.48A

Fig-5:P-Vcurveofarrayatdifferenttemperature

(irradianceG=1000W/m2)

Fig-6:P-Vcurveofarraywhenirradiancechangeand

(temperatureT=25°C)

2.2DC-DCBoostConverter

According to working operation if S is a switchingmoduleMOSFET,Disdutycyclewhichmeanscomparativeconduction time and if (T = ton + toff). the D is given byEquation(2):

(2)

When the switch S is on source release energy toinductor,duringthattimeinductorstoressomeenergybyproducingmagnetic field [18] [21].Whenswitch is inoffcondition that time current drain to the load. But if theimpedance is higher the current will be small. Simulinkmodel of the boost circuit is given in figure 7. Boost

converter is used as main circuit of the system. Theparameters of boost circuit are set as follow;V=90V, L=0.00015H,C=0.0009F,D=50%,R=50ohmsandF=20khz.

s

Fig-7:MATLABSimulinkmodelofBoostconverter

Fig-8:Boostcircuitoutputvoltagecurve

3. MPPT CONTROLLER BASED ON PERT ANDOBSERVE(P&O)3.2ConventionalPertandObserveP&O

P&O algorithm is used most commonly as MPPTcontroller in PV system because of its simplicity andapplicability. it works based on the perturbation andobservation of the solar irradiance direction [22]. If thephotovoltaic arraypower rise, thepoint of theoperationtowardsMPPwillgorigthusthevoltageworksinthesamedirection. when the power from PV cell reduces, theworking point of the field differs from theMPP, and thedirectionperturbationvoltagehasbecomeoverturned[23][24]. Change in the power is define from the followingformula[25]:

∆P = P(k) − P(k − 1) (3)AdisadvantageoftraditionalP&OMPPTmethodisthe

steady state oscillation in output power during trackingnewMPPwhenweatherchangesandtheresponseof thesystemalsoveryslow.P&Oalgorithmisgiveninfigure9.

0 10 20 30 40 50 60 70 80 90 100Voltage (V)

0

2

4

6

8

10

12

Cur

rent

(A

)

40 oC

35 oC

25 oC15 oC

0 oC

0 10 20 30 40 50 60 70 80 90 100Voltage (V)

0

200

400

600

800

1000

Pow

er (

W)

40 oC35 oC25 oC15 oC0 oC

0 10 20 30 40 50 60 70 80 90Voltage (V)

0

2

4

6

8

10

12

Cur

rent

(A

)

1 kW/m2

0.8 kW/m2

0.4 kW/m2

0.1 kW/m2

0 10 20 30 40 50 60 70 80 90Voltage (V)

0

200

400

600

800

Pow

er (

W)

1 kW/m2

0.8 kW/m2

0.4 kW/m2

0.1 kW/m2

on on

on off

T TDT T T

= =+



816

Fig-9:P&Oalgorithm

Simulationmodelofthephotovoltaicsystemwithboostconvertercircuit,conventionalP&Osimulationcircuitandthe result of output power characteristic curve is givenbelow. Parameters of the circuits are explained in abovedetail.simulationtimeisset0.2s–0.5s.

Fig-10:SimulationmodelofconventionalP&O

Fig-11:Outputpowercurve

Abovefigure11,isoutputpowercurveofphotovoltaic

system based on the conventional P&O control MPPTtechnique.Inthiscasetemperatureisconstantat25°Candlightintensityisstableat1000W/m2.

Fig-12:Outputpowercurvewhentemperatureis25°C

andlightintensitychange.

Fig-13:Outputpowercurvewhenlightintensityisstable

1000W/m2andtemperaturevary

3.3ModifiedPertandObserveP&OThe improvedmethod is designed to prevent ripples

when trying to identify the maximum power point of atraditionalalgorithmandtoidentifythepointmorequicklyafter a major power change. In this method, representspowerchangeis:

∆P = P>?@ − P%AB (4)

The improvedmethod has unique feature,which setsthe array corresponding reference voltage to themodulepeak voltage. The PI controller then transfers the arrayoperatingpointtothatspecificvoltagelevel[26].Whentheexternalenvironmentchangesandreferencevoltageofcelland converter is boosted or reduced accordingwith thispowerchange, it canbe seen from thesimulation resultsthatfluctuationisreducedandnextMPPistrackedsooner.DuringstableweatherconditionwhennopowerchangenoiterationisexecutedandrippleacrossMPPareabolished.Simulation model of the improved technique with PIcontrollerisshowninfigure14below.Simulationresultsaregivenasfollow.

1PWM

2Ipv

1Vpv

D P

PWM Generator(DC-DC)

> 0

0

*1,

V

ΔV4

product2 > 0

> 0

1e-3

constant1

0.5

constant2

ADD2

ΔV3

2duty cycle



817

Fig-14:SimulationmodelofimprovedP&O

Fig-15:Outputpowercurve(weatherstable)

Fig-16:Outputpowercurvewhentemperatureis25°C

andlightintensitychange.

Fig-17:outputpowercurvewhenlightintensityremains=1000W/m2andtemperaturevary

4. COMPARATIVE ANALYSIS OF MPPT CONTROLTECHNIQUESIMULATIONRESULTSThroughtheexperimentalanalysisitcanbeevaluatedthattheresponsetimeoftheimprovedpertandobserveP&OMPPT technique is faster than the conventional method.Forbetterunderstandingcomparisontableisgiven.

Table-2:ComparisonofMPPTresultsbetweentraditionalP&OMPPTandimprovedP&OMPPT

MPPTTechnique Improved

P&OMethodTraditionalP&OMethod

TrackingTimewhentheEnvironmentisStable

0.012s 0.025s

OutputPower 743W 738.5W

TrackingwhenLightIntensityDrops

0.022s 0.05s

OutputPower 620.5W 605W

TrackingwhenLightIntensityIncreases

0.016s 0.018s

OutputPower 743W 738.5W

It can be seen from the simulation result during stableweather condition the improved method track MPP in0.012s.AsmallfluctuationcanbeseenaroundMPPbutitmaintainsstablepoweroutput743Wat0.03s.Ontheotherhand, conventional method finds MPP in 0.025s and itsoutput fluctuate for long time, after 0.07s it gives stableoutput power 738.5W. Moreover, during unstableconditiontheimprovedmethodtracknewMPPextremelyfastascomparetoconventionalmethod.Inthisconditionittakes0.001s-0.006stogivestableoutput.MaximumpoweroutputofthePVarrayis760W,whentemperatureis25°Cand light intensity is 1000W/m2. So, the efficiency ofimprovedmethodisabout97.7%andconventionalmethodis 97.17%. The response time of improved method tofindingMPPisdoubledthantheconventionalmethod.

5.CONCLUSIONSInthispaper,tostartwiththeintroductionofPhotovoltaicsystem.AccordingtotheworkingprincipledifferenttypesofPVsystemareanalyzed.SimulationmodelofDCBoostcircuitandPVarrayarestudied.Themodelofconventionaland improvedmethod issimulated inMATLAB/Simulink.Theresultsshowthatwhen thesolar irradiance increasethe output power of PV array increase. Later on, aftercomparison, results shown the advantages of improvedmethodoverconventionalmethod.

1Ipv

0.2

deltaD

2Vpv

Ib

Vn

D+ΔD

v

> 0

D P

PWM Generator(DC-DC)

In

Dsample

Vb

Pb

Pn

ΔP

> 0

> 0

Db

D-ΔD

1 PWM

PI(z)



818

ACKNOWLEDGEMENTWiththegraceofAlmightyLord,undersupervisionofMa’amDr. YajunWang andmy GrandpaMr. KhiyalBadShahwhogrownmeupwithgreatloveandcarethroughoutmylife.

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maximum power point technique (mppt) for pv system based ... · power point) control algorithm to...

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