Design and control of a standalone PV water pumping system

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ScienceDirect

JournalofElectricalSystemsandInformationTechnologyxxx(2016)xxx–xxx

Design

and

control

of

a

standalone

PV

water

pumping

system

Essam

E. Aboul

Zahab

a

,

Aziza

M. Zaki

b

,

Mohamed

M. El-sotouhy

b,∗

Q1

a_Department_of_Electrical_Power_and_Machines,_Faculty_of_Engineering,_Cairo_University,_Giza,_Egypt

b_Department_of_Power_Electronics_and_Energy_Conversion,_Electronics_Research_Institute,_Dokki,_Giza,_Egypt

Received5October2015;receivedinrevisedform22February2016;accepted6March2016

Abstract

Waterresourcesarevitalforsatisfyinghumanneeds.However,almostone-fifthoftheworld’spopulation–about1.2billion

people–liveinareaswherewaterisphysicallyrare.Onequarteroftheglobalpopulationalsoliveindevelopingcountriesthat

facewatershortages.ThispaperpresentsstandalonePVwaterpumpingsystem.Photovoltaic(PV)isthemainpowersource,and

leadacidbatteriesareusedasenergystoragesystem,tosupplyawaterpumpdrivenbyaBLDCmotor.Theproposedcontrol

strategyconsistsofthreecontrolunits.ThefirstunitistocontrolthespeedandhysteresiscurrentcontrollerforBLDCmotor.The

maximumpowerpointtracking(MPPT)isthesecondcontrolunit,andthebatterycharging/dischargingsystemiscontrolledbythe

thirdcontroller.Thesimulationresultsshowtheeffectivenessandthegoodefficiencyoftheproposedsystem.

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undertheCCBY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).

Keywords: Photovoltaic(PV);Brushlessdirectcurrent(BLDC);Perturbandobserve(P&O);Fuzzylogiccontroller(FLC);Alternativecurrent (AC);Directcurrent(DC);Stateofcharge(SOC)

1. Introduction

Waterresourcesarevitalforsatisfyinghumanneeds,protectinghealth,andguaranteeingfoodproductionenergy

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andtherebuildingofecosystems,aswellasforsocialandeconomicdevelopmentandforsustainabledevelopment. Q4

However, accordingtoUNWorldWater Development Reportin2015,almostone-fifth of the world’spopulation (about 1.2billion people)live inzoneswherewater isphysically rare. Onequarter of the global population also liveindevelopingcountriesthatfacewatershortages(TheUnitedNationsWorldWaterDevelopmentReport,2015). Remotewaterpumpingsystemsareabasicchoiceinmeetingthisneed.Installationofanewtransmissionlineand atransformertothe remoteareasis oftenveryexpensive(Hmidet etal.,2014).Also thecostsof fossil fuelsand theirenvironmentalimpactsrise,thedemandforrenewableenergysourcesincreases(AashoorandRobinson,2013; SreekumarandBenny,2013).Ifthesourceofwateris1/3mile(app.0.53km)ormoreawayfromthepowerline,

∗_{Corresponding}_author.

E-mailaddress:[email protected](M.M.El-sotouhy). PeerreviewundertheresponsibilityofElectronicsResearchInstitute(ERI).

http://dx.doi.org/10.1016/j.jesit.2016.03.003

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Fig.1.Theproposedsystem.

photovoltaic(PV)ispreferredasaneconomicchoice(Oi,2005).Therearemanytechniquesformaximizingtheoutput powerfromthePVmoduleseitherconventionaltechniqueslikeperturbandobserve(P&O)orintelligenttechniques likefuzzycontrol(SreekumarandBenny,2013).Thephotovoltaicpumpinghasturnouttobeoneofthemostfavorable fieldsinphotovoltaicapplications.ForastandalonePVsystemtherearemainlytwotypesofpumps:centrifugaland positivedisplacementpumps.In the centrifugalpump,the rotation ofan impellerforceswater intothe tube. The waterspeedandpressuredependontheavailablemechanicalpowerattherotatingimpellerandthetotalhead,but thedisplacementpumpusesapistonorascrewtocontrolthewaterflow.Thepositivedisplacementpumpgrantsa betterefficiencyunderlowpowerconditionsthanthecentrifugalpump.Thewaterpumpsmaybedrivenbymany typesofdrivingsystems.Themorepopulararedirectcurrent(DC)motors,alternativecurrent(AC)motorsorBLDC motors(Mohammedietal.,2013).BrushlessDC(BLDC)motordriveshavereceivedwidecareastheirperformance issuperiortothoseofconventionalbrushedDCmotorsandACmotors.Insmallunitsupto5.0kW,BLDCmotorsare preferableandhaveincreasedtherequestinwaterpumpingsystemsoperatedbyaphotovoltaicarraybecauseoftheir higheroperatingefficiencyandgoodstartingtorque(PuttaSwamyetal.,1995).Hysteresiscurrentcontrolisoneof thesimplePWMcurrentcontroltechniqueswhichareusedforminimizingcommutationtorqueripple,andareeasy toimplement(DasandChanda,2014).Asphotovoltaicproduceselectricityonlywhenthesunlightexists,sostand alonePVsystemsneedabackupenergystoragewhichmakesitavailablethroughthebadweatherornightconditions. InstandalonePVsystems,amongmanypossiblestoragemediums,batteriesarecommonlyusedasastorageelement. Thelead-acidbatteryismostcommonusedwithstandalonePVsystemsbecauseitisquitecheapandbroadlyavailable (JaycarElectronicsReferenceDataSheet,2016).ThispaperpresentsanefficientPVwaterpumpingsystem.Itprovides theoreticalstudiesandmodelingforallthesystemcomponents,comparisonbetween(P&O)&fuzzymaximumpower pointtechniques,andprovidesthemotorperformance(speed,torque,etc.)results.

2. Theproposedsystem

Thestand-alonePVwaterpumpingsystemconsistsofasinglePVmoduleof300Wrating,amaximumpower pointtracking,abatterybankwithchargingcontroller,BLDCmotordrivingapositivedisplacementpump,andBLDC motorcontrollerasshowninFig.1.

2.1. PVmodulemodel

TherearevarioussizesofPVmoduleavailableinthemarket.Usually,anumberofPVmodulesarecombinedas anarray(eitherseriesorparallelconnection)tomeetdifferentenergydemands.ThesizeofthePVmoduleselected fortheproposedsystemis300Wmodule.TheselectedmoduleisIS4000P300Wmulti-crystallinePVmodule.As showninFig.2,themodelofthePVmodulecanberepresentedasshownintheequivalentcircuit(Fig.2)asacurrent sourceinparallelwithadiode(Mahmoudetal.,2012).

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Fig.2.ThePVmodelanditssimulatedelectricalcharacteristics.

Fig.3.Generalmodelofbattery.

The PV cellelectricalcharacteristics are nonlinear and varyaccording tothe solar insolation (G) andthe cell temperature(T).ThePVoutputcurrentIpvcanbestatedbyEq.(1).

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Ipv =Iph−I0(e(

q×Vpv

nKT )−₁₎ ₍₁₎

whereIpvistheoutputcurrentfromthePVcell,Iphisthephotogeneratedcurrent,I0isthesaturationcurrentinthe

dark,qistheelectroncharge=1.6×10−19(C),VpvistheoutputvoltageofthePVcell,nisthediodeidealityfactor,K

isBoltzmannconstant=1.38×10−23(J/K),Tisthecelltemperature(◦C).ThePVmoduleoutputcurrentofanumber ofcellsconnectedinseries(Ns)andnumberofcellsconnectedinparallel(Np)canbestatedbyEq.(2).

Ipv =NpIph−NpI0(e(

q×Vpv

Ns×n×K×T)−₁₎ ₍₂₎

The simulated electrical characteristics of the adopted PV module at standard conditions (irradi-ance=1000W/m2&temperature=25◦C)areshowninFig.2.

2.2. Batterymodel

Thebatteriesareusedfor storetheexcesspowerandsupplyittotheloadinbadweatherconditionsor innight periods.Inthestandalonephotovoltaicsystemsthecommercialrechargeablebatteriesinthemarketare:lead-acidor (Pb-S),thenickel-cadmiumor(NiCad),thenickel-metalhydrideor (NiMH),andthelithium-ionor(Li-ion)types. Lead-acidbatteriesarethemostpopular,andwidelyusedinrenewableenergysystems.Theequivalentcircuitofa generalbatterydynamicmodelparameterizedtocharacterizemostpopulartypesofrechargeablebatteries.Thismodel canberepresentedbyasimplecontrolledvoltagesourceinserieswithaconstantresistance,asshowninFig.3,and describedbyEqs.(3)&(4)(Tremblayetal.,2007).

E=E0−K Q Q− idt +Aexp(−B idt) (3) Vbat.=E−i×R (4)

whereEistheno-loadvoltage(V),E0isthebatteryconstantvoltage=12V,Kisthepolarizationvoltage(V),Qis

thebattery capacity(Ah),idtistheactualbatterycharge(Ah),Aistheexponentialzoneamplitude(V),Bisthe

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Fig.4.Circuitdiagramofdeltaconnectedmotor.

exponentialzonetimeconstantinverse(Ah)−1,Vbatisthebatteryvoltage(V),Ristheinternalresistance(ohm),iis

thebatterycurrent(A).

2.3. BLDCmotormodel

Threephase BLDCmotorconnectionmaybestaror deltaconnected,the motorused inthe simulationisdelta connectedasshowninFig.4.

ThelinetolinevoltagesandBEMFsarethesameasphasevoltagesandBEMFs(PillayandKrishnan,1989a,b). SupposeLab=Lbc=Lca=L,andRab=Rbc=Rca=R.

V1=i1R+L di1 dt +e1 (5) V2=i2R+L di2 dt +e2 (6) V3=i3R+L di3 dt +e3 (7)

whereListhearmatureself-inductance[H], Risthearmatureresistance[],Va,Vb,Vcaretheterminalphasesor

linesvoltages[V],i1,i2,i3aremotorinputcurrents[A],ande1,e2,e3aremotorback-EMFs[V].Inthe3-phaseBLDC

motor,theback-EMFisrelatedtoafunctionoftherotorpositionandtheback-EMFofeachphasehas120◦phase angledifferencesotheequationofeachphaseshouldbeasfollows:

ea = Kwf(θe)ω (8) eb= Kwf(θe−120)ω (9) ec= Kwf(θe−240)ω (10) e1=ea−eb (11) e2=eb−ec (12) e3=ec−ea (13)

whereKwisthebackEMFconstantofonephase[V/rads−1],θeistheelectricalrotorangle[◦el.],ωistherotorspeed

[rads−1],ea,eb,ecaretrapezoidalfunctionswith120◦flattop,theelectricalrotorangleisequaltothemechanical

rotoranglemultipliedbythenumberofpolepairsp:

θe= _p 2 θm (14) 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105

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whereθmisthemechanicalrotorangle[rad].

ThefunctionF(θe)givesthetrapezoidalwaveformoftheback-emf.Oneperiodofthisfunctioncanbewrittenas:

f(θe)= ⎧ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎨ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎩ 1 0≤θ< 2π 3 1−6 π θe− 2π 3 2π 3 ≤θ<␲ −1 ␲≤θ< 5π 3 −1+ 6 π θe+ 2π 3 5π 3 ≤θ<2␲ (15)

Totaltorqueoutputcanberepresentedasthesummationofthatofthe3phases.Nextequationrepresentsthetotal outputtorquein[Nm]:

T = eaia+ebib+ecic

ω (16)

Themechanicalequationofthemotorisasfollows:

Te −Tl =J dω dt + βω (17)

Sothemotorspeedcanbecalculatedas:

ω=

(Te−Tl−βω)

J (18)

whereTlisthepumploadtorque[Nm],Jistheinertiaofrotorandcoupledshaft[kgm2],βisthefrictionconstant [Nmsrad-1].Thentherotorpositioniscalculatedbyintegratingthespeedofthemotor,andthenwecouldcalculate thephasecurrentsandlinecurrentsbyapplyingKirchhoff’slawatthreenodes(a–c).Theselinecurrentsarefeedback tothehysteresiscurrentcontroltogetthestateofthetransistors.

3. Controlstrategy

Inthisworkthecontrolstrategyisdividedintothreemaincontrolunits.(1)Firstcontrol unitisresponsiblefor speedandhysteresiscurrentcontrolfortheBLDCmotorpump,(2)secondcontrolunitisresponsibleforMPPT,and (3)thirdcontrolunitisresponsibleforcharginganddischargingofthebatterybank.

3.1. SpeedandhysteresiscurrentcontrolfortheBLDCmotorpump

Fig.5describesthebasicblocksofthePMBLDCMdrive.Thedrivecontainsspeedcontroller,referencecurrent generator,PWMcurrentcontroller,positionsensor,themotorandtheinverter.Thepurposeofamotorspeedcontroller istoyieldasignalrepresentingtherequiredspeed,andtodriveamotoratthatspeed.Speedcontrollercalculatesthe differencebetweenthereferencespeedandtherealspeedproducinganerror,whichisfedtothePIcontroller.The parametersofthePIcontrollersareobtainedbyusingtrialanderrormethod.PIcontrollersareusedwidelyformotion controlsystems.Thecontrollertriestominimizetheerrorbyadjustingtheprocesscontrolinputs.Heretheproposed techniqueconsistsoftheouterspeedloopandoneinnercurrentloopasthedouble-loopcontrolsystemisintroduced, showninFig.5.Inthedouble-loopcontrolsystem,aPIcontrollerisadoptedinthespeedloopandahysteresiscurrent controllerisadoptedinthecurrentloopontheprincipleofhysteresiscurrenttrackcurrentcontrolledvoltagesource inverter(SanitaandKuncheria,2013).HysteresiscurrentcontrolisoneofthesimplePWMcurrentcontroltechniques whichareusedforminimizingcommutationtorqueripple,anditiseasytoimplement.Thissimplecontrolstrategy willbepresentedatlowcostandusessimplestructureandrequiresminormemoryorprocessingabilities.Thistypeof BLDCdriveisverysuitableforrenewableapplications.Althoughhysteresiscontrolisinsensitivetomotorparameter variations,thestabilityofitsnormaloperationshastobeconfirmed(DasandChanda,2014).

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Fig.5.ThebasicblocksoftheBLDCmotordrive.

Table1

Thereferencecurrentdependingonrotorposition.

Q8 Rotorposition(θ) Referencecurrents I∗a I∗b I∗c 0≤θ<π/3 Is −Is 0 π/3≤θ<2π/3 Is 0 −Is 2π/3≤θ<π 0 Is −Is π≤θ<4π/3 −Is Is 0 4π/3≤θ<5π/3 −Is 0 Is 5π/3≤θ<2π 0 −Is Is Table2

Hysteresiscurrentcontrollogic(PuttaSwamyetal.,1995).

Ix Switch

Q1 Q2 Q3 Q4 Q5 Q6

IA>h ON OFF OFF OFF OFF OFF

IA<−h OFF OFF OFF ON OFF OFF

IB>h OFF OFF ON OFF OFF OFF

IB<−h OFF OFF OFF OFF OFF ON

IC>h OFF OFF OFF OFF ON OFF

IC<−h OFF ON OFF OFF OFF OFF

3.3.1. Referencecurrentgenerator

Theinputsignalsneeded for generatingthe referencecurrents(I∗a, I∗b,I∗c)are the rotorposition (θ),andthe

magnitudeofthethreephasecurrents(I∗)generatedfromEq.(19):

I∗=T

∗

Kt

(19) whereKtisthetorqueconstant,T∗isthereferencetorquevaluegeneratedfromthePIspeedcontroller.Thereasonthat

thisiscalledahysteresiscontrolleristhatthephasevoltageswitchestoretainthephasecurrentswithinthehysteresis bands.Thehysteresisbandhasawidthequal2h.Hysteresiscurrentcontrolcanbeimplementedbycomputingreference currentI*xasshowninTable1andmeasuringtheactualcurrentIxwherex=a,b,orcandthencalculateerrorsignal

Ix=I*x−IxandthenapplythelogicshowninTable2,whichactivatetheswitchesshownaboveinFig.5.The

referencecurrentvaluescanbecreatedwithrespecttotherotorpositionasshowninTable1(PuttaSwamyetal.,1995; PillayandKrishnan,1989a).

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Fig.6.Perturbandobservealgorithm(P&O)(Oi,2005).

Thehysteresiscurrentcontrollergivestheswitchingof6switchestotheinverterdevicesshownupinFig.4.The switchinglogicisformulatedasgiveninTable2.

3.2. TheMPPTcontrolunit

TheMPPTcontrolunitisusedtokeeptheoutputpowerofthePVasmaximumaspossible.Thiscontrolunitis implementedusingtwoMPPTalgorithms:(1)P&Oand(2)FLCasfollows:

3.2.1. P&Oalgorithm

InthismethodthePVoutputcurrentandvoltagearemeasured(Ipv,Vpv),andtheoperatingvoltage(Vpv)isperturbed

(increased)byasmalldecreaseinthedutycycleDbyarate(dD)oftheboostconverterandobservingthechangein powerandthechangeinvoltagethencalculatethe(dP/dV)value.If(dP/dV)ispositivetheperturbationoftheoperating voltagewillbeinthesamewayofincreasingsoshouldcontinuedecreasingthedutycycleoftheboostconverter.If dP/dVisnegativetheoperatingvoltageshouldbeperturbedinthereversedirection(decreased).Themaximumpower pointisobtainedwhendP/dV=0.TheflowchartofthisalgorithmisshowninFig.6.(Oi,2005;Elgendyetal.,2012).

3.2.2. FLCbasedMPPTalgorithm

Fuzzylogiccontrol (FLC) isused largely incontrol engineeringandisvery importantwhen thereis noexact mathematicalmodelorwhilethecontrolledprocessisnonlinear(Rebhietal.,2013).Fuzzylogiccontrollerhasbeen largelyusedforindustrialprocessesintherecentyearsduetoitssimplicityandeffectivenessforbothlinearand non-linearsystems.Itconsistsofthreeblocks:Fuzzification,Fuzzyrulesandinferenceengine,andfinallyDefuzzification (AashoorandRobinson,2013).

3.2.2.1. Fuzzification. Inthefuzzificationstage, numericalinputvariablesaretransformedintolinguisticvariables basedonsubsetscalledmembershipfunction.TheproposedfuzzylogiccontrollerhastwoinputvariablesdPpv &

dIpv,andoneoutputvariabledD:

dPpv = Ppv(k)−Ppv(k−1) (20)

dIpv = Ipv(k)−Ipv(k−1) (21)

dD = D(k)−D(k−1) (22)

wheredPisthechangeinPVpower,dIisthechangeinPVcurrentanddDisthechangeindutycycle.Fig.7shows themembershipfunctionsofthetwoinputsandtheoutputfuzzysets.Eachfuzzysethasfourmembershipfunctions asfollows:PB(PositiveBig),PS(PositiveSmall),NS(NegativeSmall)andNB(NegativeBig).

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-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 x 10-3 0 0.2 0.4 0.6 0.8 1 dD D e g ree of m e m b e rs h ip b p s p s n b n -5 -4 -3 -2 -1 0 1 2 3 4 5 0 0.2 0.4 0.6 0.8 1 dp Degree of membership NS PS PB B N -0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1 0 0.2 0.4 0.6 0.8 1 dI Degree of membership B P S P S N B N

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Table3 Fuzzyrules. dI dP PB PS NS NB PB PB PS NS NB PS PB PS NS NB NS NB NS PS PB NB NB NS PS PB

Fig.8.Intermittentcharging&dischargingcontrol.

3.3.2.2. Fuzzy rulesandinferenceengine. Fuzzyrulesincludeasetofrulesinlinguisticformwhichsubordinate thefuzzyinputswiththefuzzyoutput.Thesearecreatedbyanexpertknowledgeandunderstandingofthesystem performancethatisessentialtorealizethecontrolobjectives.Thefuzzycontrolruleshavebeenestablishedusinga setofIF-THENrulesasdefinedinTable3.

3.2.2.3. Defuzzification. In the defuzzificationstep the output of fuzzy logiccontrol is converted from linguistic variables tonumericalvariables, where inthisprocess the crisp output of the FLC (dD) is calculated. Thereare differentapproachesfordefuzzifyingaresultfuzzyset.ThemethodusedinthispaperiscalledtheCenterofGravity (AashoorandRobinson,2013).FLCcantracktheMPPrapidlywithsmalloscillationsaroundit(Mansouretal.,2015).

3.3. Thebatterybankcharginganddischargingcontroltechnique

Therearemanybatterychargingalgorithmsusedtokeepthebatteryatahighstateofchargeandincreasethelife timeofthebattery. Theintermittentchargingcontrolisthemostgenerallyusedtechniqueincommercialchargers (Armstrongetal.,2008).Inthechargingmode,thebatteryischargedwithmaximumpowerpointtracking(MPPT) betweentwopredefinedvoltageedgesasshowninFig.8.Whenthebatteryreachestheuppervoltageedge,atpoint 1,thechargingisstopped,thenthebatteryvoltageisobserveduntilitdropstothelowervoltageedge,atpoint2,then thechargingbeginsagain.Thesameprocessisrepeatedatthedischargingmodeprocesstoprotectthebatterybank fromdeepdischarging,whenthebatteryvoltagereachestheedgepoint4thedischargefrombatterybankshouldstop, andrepeatdischargingfrombatteriesaftertheirvoltagebecomelargerthanorequaltothevoltageatedgepoint3.So, wecouldprotectthebatterybankfromovercharginganddeepdischarging.

4. Simulationresults

ThesystemissimulatedintheMATLAB/SIMULINKprogramwithsampletimeequaltotwomicrosecondsusing twoMPPTtechniques(P&O,andfuzzy)usingthesamemotorcontrol(outerspeedcontrol,innerhysteresiscurrent controller). 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197

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Fig.9.Motorratedspeedandratedtorque. 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 -8 -6 -4 -2 0 2 4 6 8 time (sec) 3 ph as e c u rr e n t (A )

Fig.10.Motorthreephaseratedcurrents.

4.1. BLDCmotorpumpsimulationresults

SupposethemotorworksatnominalspeedandatnominalvoltageasinAppendixA.Theratedspeedandrated torque,thethreephasecurrents,rotorposition,andBEMFsareshowninFigs.9–12respectively.

4.2. MPPTsimulationresultsusingP&Otechnique

Supposethemoduletemperatureisconstantat25◦Candtheirradianceisvariableandchangethroughadayas(0.4, 0.6,0.7,0.8,0.9,1,0.9,0.8,0.7,and0.3),andthestepchangeindutycycleisdD=0.001.Theresultsshowtheoutput modulepowerthroughaday(representedinsimulationtimebyonesecond)inFig.13usingP&OMPPTtechnique.

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0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 -1 0 1 2 3 4 5 6 7 time (sec) po si ti on (r ad /s e c )

Fig.11.Motorrotorpositions.

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 -40 -30 -20 -10 0 10 20 30 40 time (sec)

3 phase Back EMF (V)

Fig.12.MotorthreeBEMFs.

4.3. MPPTsimulationresultsusingfuzzytechnique

Supposethemoduletemperatureisconstantat25◦Candtheirradianceisvariableandchangethroughdayas(0.4, 0.6,0.7,0.8,0.9,1,0.9,0.8,0.7,and0.3).Theresultsshowtheoutputmodulepowerthroughaday(representedin simulationtimebyonesecond)withMPPTusingfuzzyintelligenttechniquesshowninFig.14.

4.4. Simulationresultsofbatteryintermittentchargingcontrolalgorithm

Theintermittentchargingcontrol hastwobandstoprotectthebattery fromoverchargingwherebatteriesSOC supposed(98:100%)andlowerbandtoprotectthebatteriesfromthedeepdischargingwherebatteriesSOCsupposed (25:20%).

Supposethebatteriesinitialstateofcharge(SOC)is30%,andtheweatherisbadoratnight,thenthebatteries dischargeuntiltheSOCbecomes≤20%(atpoint4)herestopthedischargeprocessbyswitchingoffaswitchsupposed it(s2).Andwhenthebatteryrechargesagain,thesupposedswitch(s2)becomesONbutaftertheSOCreaches≥25%

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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 50 100 150 200 250 300 time (sec) P o we r (W )

Fig.13.ModuleoutputpowerthroughadaywithMPPTusingP&Otechnique.

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 50 100 150 200 250 300 time(sec) Mo d u le ou tp u t po we r( W)

Fig.14.ModuleoutputpowerthroughadaywithMPPTusingfuzzyintillegenttechnique.

(atpoint3) whichrepresentminimumallowablebatterychargingwhiledrivingtheload. Alsosupposethe battery continuechargingtillreaching themaximumchargingvalueofthe upperband100%(atpoint1). Inthiscasewe shoulddisconnectthecurrentsuppliedtothebatteriestoprotectthemfromoverchargingbyswitchingOFFasupposed switch(S1),andreswitchingitONagainiftheSOCislowerorequaltotheminimumupperband98%(atpoint2)as showninFig.15,andthesupposedswitchS2isatONstateasshowninFig.16.

5. Discussionandconclusions

ThestandalonePVwater pumpingsystemusedisdescribed first.Itconsists of aPV array,amaximumpower pointtracking(MPPT)systemcontrollingaDC–DCboostconverterwhichdrivesaBLDCmotordrivingapositive displacementwaterpump.TwoMPPTtechniquesareintroducedP&OmethodandFLCmethod,andthetwomethods arecompared.FromthesimulationresultsitcanbenoticedthatFLCisfasterandhasloweroscillationaroundthe maximumpowerpointthantheP&O.Thebatterybackingsystemisalsodesignedtogetherwithitscontrolsystem tosatisfysystemrequirementsallthetime.Simulationresultspresentingthesystemperformancewerepresentedand discussed.Byapplythissysteminmultipleorlargescalesystemcouldsolvetheproblemofwaterinremoteareas

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0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 x 104 0 10 20 30 40 50 60 70 80 90 100 time(sec)

Battery SOC(%)&Switch(S1) status

Switch (s1) status battery SOC(%)

Fig.15.BatterySOC(%)withswitch(S1)status.

Fig.16.BatterySOC(%)withswitch(S2)status.

andcouldextractitforone-fifthoftheworld’spopulation(about1.2billionpeople)wholiveinzoneswherewateris physicallyrare.

AppendixA. BLDCmotorparameters

Q7

Motordata Unit Value

Numberofpairpoles 1

Powerrating W 101

Nominalvoltage V 48

Ratedspeed rpm 10,000

Ratedtorque mNm 40

Noloadcurrent A 0.109

Terminalresistancephasetophase Ohm 4.4

Terminalinductancephasetophase mH 0.678

Torqueconstant mNm/A 37.02

BEMFconstant mV/rpm 3.877

Rotorinertia gcm2 34

Frictiontorque mNm/rpm 2.4×10−4

229 230

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References

Aashoor,F.A.O.,Robinson,F.V.P.,2013.Maximumpowerpointtrackingofphotovoltaicwaterpumpingsystemusingfuzzylogiccontroller.In: IEEE48thInternationalUniversities’PowerEngineeringConference(UPEC),2–5September,pp.1–5.

Armstrong,S.,Glavin,M.E.,Hurley,W.G.,2008.Comparisonofbatterychargingalgorithmsforstandalonephotovoltaicsystems.In:IEEEPower ElectronicsSpecialistsConference(PESC),15–19June.

Das,Bikram,Chanda,Mahua,2014.TorqueripplereductionandspeedperformanceofBLDCMdrivewithhysteresiscurrentcontroller.Int.J.Eng. Res.Technol.(IJERT)3(May(5)),194–201.

Elgendy,M.A.,Zahawi,B.,Atkinson,D.J.,2012.EvaluationofperturbandobserveMPPTalgorithmimplementationtechniques.In:6thIET InternationalConferenceonPowerElectronics,MachinesandDrives,27–29March,pp.1–6.

Hmidet,Ali,Gammoudi,Rabiaa,Hasnaoui,Othman,Dhifaoui,Rachid,2014.AnalogMPPTcontrollercircuitusedinphotovoltaicpumpingsystems. In:IEEEFifthInternationalRenewableEnergyCongressIRECHammamet,Tunisia,25–27March.

JaycarElectronicsReferenceDataSheet,ChoosingaRechargeableBattery.http://www.jaycar.com/imagesuploaded/recharge.pdf.

Mahmoud,Yousef,Xiao,W.,Zeineldin,H.H.,2012.Asimpleapproachtomodelingandsimulationofphotovoltaicmodules.IEEETrans.Sustainable Energy3(January(1)),185–186.

Mansour,AtefM.,Faris,KhaledN.,El-DinAboulZahab,Essam,2015.Smartenergymanagementcontrollerforamicrogrid.Int.J.Eng.Res. (IJER)4(8),456–464.

Mohammedi,Ahmed,Rekioua,Djamila,Mezzai,Nabil,2013.ExperimentalstudyofaPVwaterpumpingsystem.J.Electr.Syst.9(2),212–222. Oi,Akihiro,2005.Designandsimulationofphotovoltaicwaterpumpingsystem.In:AThesisPresentedattheFacultyofCaliforniaPolytechnic

StateUniversity,SanLuisObispo,September.

Pillay,Pragasen,Krishnan,Ramu,1989a.Modeling,simulation,andanalysisofpermanent-magnetmotordrives,PartI:thepermanent-magnet synchronousmotordrive.IEEETrans.Ind.Appl.25(March/April(2)),265–273.

Pillay,Pragasen,Krishnan,Ramu,1989b.Modeling,simulation,andanalysisofpermanent-magnetmotordrives,PartII:thebrushlessDCmotor drive.IEEETrans.Ind.Appl.25(March/April(2)),274–279.

PuttaSwamy,C.L.,Singh,B.,Singh,B.P.,1995.DynamicperformanceofapermanentmagnetbrushlessDCmotorpoweredbyaPVarrayfor waterpumping.Sol.EnergyMater.Sol.Cells36(2),187–200.

Rebhi,Mhamed,Benatillah,Ali,Sellam,Mabrouk,Kadri,Boufeldja,2013.ComparativestudyofMPPTcontrollersforPVsystemimplementedin theSouth-westofAlgeria.EnergyProcedia36,142–153.

Sanita,C.S.,Kuncheria,J.T.,2013.ModellingandsimulationoffourquadrantoperationofthreephasebrushlessDCmotorwithhysteresiscurrent controller.Int.J.Adv.Res.Electr.Electron.Instrum.Eng.(IJAREEIE)2(June(6)),2461–2470.

Sreekumar,Shilpa,Benny,Anish,2013.Maximumpowerpointtrackingofphotovoltaicsystemusingfuzzylogiccontrollerbasedboostconverter. In:IEEEInternationalConferenceonCurrentTrendsinEngineeringandTechnology,ICCTET’13,Coimbatore,India,3July.

The United Nations World Water Development Report, 2015. Water for a Sustainable World. http://unesdoc.unesco.org/images/0023/ 002318/231823E.pdf.

Tremblay,Olivier,Dessaint,Louis-A.,Dekkiche,Abdel-Illah,2007.Agenericbatterymodelforthedynamicsimulationofhybridelectricvehicles. In:IEEEVehiclePowerandPropulsionConference,9–12September,pp.284–289.

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