an artifical intelligent controller for 3 phase inverter based solar pv system using boost converter

7/27/2019 An Artifical Intelligent Controller for 3 Phase Inverter Based Solar Pv System Using Boost Converter

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IEEE- Fourth International Conference on Advanced Computing, ICoAC 2012MIT, Anna University, Chennai. December 13-15, 2012

An Artificial Intelligent Controller for a ThreePhase Inverter based Solar PV System using BoostConverterVasantharaj Subramanian', SasikumarMurugcsan

IpG Scholar, Dept. of Electrical and Electronics Engineering, Jeppiaar Engineering College, Chennai, Indiavasantharaj l18@gmail .com2Professor & Head, Dept. of Electrical and Electronics Engineering, Jeppiaar Engineering College, Chennai, [email protected]

Abstract: In this paper, the effectivenessofthe soft switching controlstrategies for the Three Phase Inverter based Solar EnergyConversion system with boost converter was explained. The solarirradiation and temperature are mainly depends on the output powerproduced from the PV conversion process. The Boost Converter isused to obtain the maximum power and is controlled by the Fuzzylogic controller. The Sinusoidal Pulse Width Modulation (SPWM)produces the soft switching control strategy for the proposedtopology. The proposed system involves a Stand-Alone PhotovoltaicSystem, Boost converters, Fuzzy Logic Controller, Three Phaseinverter and a load. The regulated voltage and current from theboost converter isfed to the inverter circuit which is connected to theload with a continuous maximum power. The fuzzy logic controlleris used to improve the boost converter efficiency and the sinusoidalPWM is used to give pulses for the inverter circuit. The inverteroutput current for driving a load should be noted such that it doesnot carry the harmonic content. However since disturbed sine waveis unavoidable under various factors it is necessary to reduce theharmonic level to obtain a highly effective output. The results aregenerated in MATLABSIMULINK and are shown.Keywords: Photovoltaic (PV), Maximum Power Point Tracking(MPPT), Fuzzy Logic Controller (FLC), Stand Alone, SinusoidalPulse Width Modulation (SPWM), Direct Current (DC), AlternatingCurrent (AC).

I. INTRODUCTIONAmong all renewable energy sources, solar power systemsattract more attention because they provide excellentopportunity to generate electricity while greenhouse emissionsare reduced. The only way of generating electricity from solarenergy will be PV cells or panels. Temperature, insolation,spectral characteristics of sunlight, dirt, shadow, etc., are themain factors to be considered for the efficiency of solar cells.The PV cells are made up of silicon, which is also used incomputer "chips". The radiation produced from the sun will beconverted into direct current (DC) by this Photovoltaic process.

978-1-4673-5584-1/12/$31.002012 IEEE

This point is known as maximum power point (MPP). Due tothis solar irradiation and the cell temperature there will a nonlinear variation in the point of locus. The MPPT is the efficientway to track the maximum available output power of the PVsystem. The PV panel module physically moves to pointdirectly at the sun and which the MPPT [1], [2] is not amechanical tracking system. The battery is directly connectedto the module and it is charging a discharged battery. Hence themodule will be operated at battery voltage. The graph (Fig 1)shows the PV module Power/Voltage/Current and thetraditional Current vs. Voltage curve for a 75W module for astandard test conditions of 25C cell temperature and1OOOW/m2 of insolation.

Fig.1 Power/voltage/current curve of a 75Watts PV panel.The above graph also shows the module voltage vs. PVmodule power delivered. The original MPPT system in a de-deconverter calculates the voltage at which the module is able toproduce maximum power.II. MODELING OF PHOTOVOLTAlC ARRAYSYSTEMThe equivalent circuit of the PV cell is shown in fig 2.


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IEEE-ICoAC 2012of the array. The cells connected in parallel which increases thecurrent and the greater output voltage will be produced by thecells connected in series. The Np parallel connections of cellcomposes the array, the PV and saturation currents may beexpressed as,

Ipv = Ipv,cen*Np (5)(6)

Fig.2 Equivalent Circuit of a PV CellThe basic equation of I - V characteristic of the ideal PV ismathematically described from the theory of semiconductors

This equations originate the I-V curve in figure 4 below,where the three outstanding points are highlighted: short circuit(O,lsc), Maximum Power Point (Vmp- Imp), and open circuit(Voc, 0).

(1)

(2)

(3)Fig.4 Characteristic I-V curve of a practical PV module

The PV panel is modeled as an equivalent current source.From the MATLAB Simulink library the mathematical modelfor the various equations describing the PV panelcharacteristics are modeled. The below fig 5 shows theequivalent circuit model of the PV panel. This simulation isdone for standard test condition (STC) when temperature is 25C and Irradiation is 1000 W/m2.

=

Where,Ipv,cell is the ~ u r r e n t generate? incident light (it isdirectly proportional to the Sun irradiation),Id is the Shockley diode equation,10cell is the reverse saturat ion or leakage current of thediode, q is the electron charge (1.60217646 x 10-19 C),k is the Boltzmann constant (1.3806503 x 10-23 J/K),T (in Kelvin) is the temperature of the p-n junction, anda is the diode ideality constant.

Ipv t, I.....---....

v V VFig.3 Origin of I -V equation of an Ideal PV cell.The fig 3 shows the origination of the I - V curve for theequation (2). Practical arrays are made up of multiple modules.The observation of the characteristics at the terminals of the PV

array requires the inclusion of additional parameters to thebasic equation.

Fig.5 Equivalent circuit of solar PV using MATLAB

V = NskT/q is the thermal voltage of the array with N, cellsconnected in series.Rs & Rp is the equivalent series and parallel resistance

Fig.6 Maximum current (1m)of Solar PV usingMATLAB


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Fig.7 Current generated by the incident light (Ipv)of PV usingMATLAB

Fig.8 Reverse saturation current (10)using MATLABIII. BLOCK DIAGRAM AND CIRCUIT DIAGRAMFOR DC - DC BOOST CONVERTERThe maximum available power will be extracted by theoperation ofPV generator at its MPP, by the role of the MPPT.The fig 9 shows the general block diagram for a MPPT solarPV system, using a general DC/DC converter [11]. This one is

connected to the PV generator, a battery and a load profile(such as a resistance, DC/DC motor). The main objective ofthis MPPT technique is to obtain the maximum power from thePV generator.

Fig.9 Block diagram of proposed method.In a boost converter [9], [11] the output is greater than the inputvoltage, hence the name "boost". A boost converter circuit isshown in the fig 1O. The operation of boost converter is dividedinto two modes.

Fig.l0 Boost Converter CircuitThe operation of boost converter can be divided into twomodes. Mode 1 begins, the MOSFET Mj is switched on at t=Oand hence the input current rises, flows through inductor LandMOSFET MI. Mode 2 begins when the MOSFET M1 isswitched off at t=tl and hence the current flowing through theMOSFET would now flow through inductor L, capacitor C,load and Diode Dm. The inductor current falls until MOSFETM1 is turned on again in the next cycle. The load whichreceives the energy from the inductor L.

IV. FUZZY LOGIC CONTROLLER (FLC)The main components which are used in fuzzy logic [5]based MPPT [3], [6] controller are fuzzification, rule-based,and inference and defuzzification which is shown in the belowfig 11. The input variables to the controller are the change inPV array power (Al'pv) and change in voltage (Avpv) whereasthe output of the controller is the step change of boost convertervoltage reference ( ~ V r e f ) . This is used to drive the boostconverter to maximize the output from solar PV panel.

Fig.ll Structure of Fuzzy Logic Controller.The variation of power ( ~ P p v ) will be in positive or in thenegative direction. The value of ( ~ P p v ) can also be small orlarge. By increasing or decreasing the reference photovoltaicvoltage variation ( ~ V p v , r e f ) the power Ppv will be increased in asmall or large way in the direction.. The control rules areindicated in Table 1 with ( ~ P p v ) and ( ~ V p v ) as inputs, while( ~ V p v , r e f ) represents the output. These inputs and outputvariables are expressed in terms of linguistic variables (such asNB (negative big), NS (negative small), Z (zero), PS (positivesmall), and PB (positive big). From these linguistic rules, theFLC proposes a variation of the reference voltage ~ V accordingto equations (vii-ix).where Ppv[k] and Vpv[k] are the powerand voltage of the photo-voltaic generator at sampled times (k),and Vpv,ref[k] the instant of reference voltage.


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V. THREE PHASE VOLTAGE SOURCE INVERTERThe circuit diagram for three-phase VSI topology is shownin fig 12 and the e igh t valid swi tch states are g iven in Table 2.As in single- phase VSIs, the switches of any leg of the inverter(Sr and S4, S3 and S6, or Ss and S2) cannot be swi tched onsimultaneously because this would result in a short circuitacros s the de link voltage supply. Similarly, in order to avoidundef ined s tates in the VSI, and thus undef ined ac output linevoltages, the switches of any leg of the inverter cannot beswitched of f s imul taneously as this wil l resul t in vol tages thatwill d ~ p ~ n d upon the respective line current polarity.

Table.1 Fuzzy Rule Table~ V p v / ~ P p v NB NS Z PS PB

NB NB NB NB NS ZNS NS NS NS Z ZZ Z Z Z PS PSPS Z Z PS PS PSPB Z PS PB PB PB

Pk -V k * Ikpv " pv pvk k k-lP pv = P pv" P pvk k k-lV pv = V pv" V pv

(7)

(8)

(9)

produce nonzero ac output voltages . The inver ter moves fromone state to another to generate a required vol tage waveform.Thus the resu lting ac ou tput line voltages cons is t of discretevalues of voltages that are Vs, 0, and -V s for the topologyshown in Fig. 9. The modulating technique is used to ensure thevalid states.Table 2. Valid switch states for a three-phase VSI

State State Switch Vab Vbe VeaNo. StatesSI, S2, 1 100 Vs 0 -VsS3 onS2, S3, 2 110 0 Vs -VsSlonS3, S4, 3 010 -Vs Vs 0S2 onS4, S5, 4 011 -Vs 0 VsS3 onS5, S6, 5 001 0 -Vs VsS4 onS6, SI, 6 101 Vs -Vs 0S5 onSI, S3, 7 111 0 0 0S5 onS4, S6, 8 000 0 0 0S2 onThe line to neutral vol tage must be dete rmined to find theline (or phase) current. There are three modes of operation in a

half - cycle and the expression for each mode will be givenbelow,During Mode I: (0 ::: rot:::n/3)

R/ 2 V R ( )Van = = -R - V = - ,Vbn = - -R - V = -2V /3 10R+(z) 3 R+(z)During Mode II: (n/3::: rot:::2n/3)

R- V RVbn= ~ n = - - - - - 1 . . . . . . - ( R ) V= - - , V a n= -R -V= 2V/3 (11)R+ z 3 R+(z)During Mode III: (2n/3::: rot::: n)

R/ 2 V R ( )Van = Vbn = - -R V =- = - -R - V = -2V/3 12R+(z) 3 R+(z)

Fig.12 CircuitDiagram for Voltage Source Inverter.Dur ing the s tates 7 & 8 (in table 2) the ac current f reewheelthrough either the upper or lower component which produceszero ac line voltages . The remain ing states (1 to 6 in Tab le 2)

VI. SINUSOIDAL PULSE WIDTH MODULATIONThe generation of gating signals with Sinusoidal PWM iss hown in fig 13. There are three sinusoidal reference wavesrv., v., and v. each shifted by 120. A carrier wave iscompared with the reference signal corresponding to a phase togenerate the gating signals for that phase. Comparing thecarri er signa l Vcr with the reference phases Vra- Vrb- and Vcrproduces SI and S3 respectively as shown in fig 13b. Theinstantaneous line - to - line output voltage is Vab = Vs(S1 -


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S3). The output voltage as shown in fig 13d is generated byeliminating the condition that two switching devices in thesame arm cannot conduct at the same time. The normalizedcarrier frequency mf should be odd multiple of three. Thus, allphase - voltage (Van, Vbn- and Ven)are identical, but 1200 out ofphase without even harmonics; moreover, harmonics atfrequencies multiple of three are identical in amplitude andphase in all phases. For instance, if the ninth harmonic voltagein phase 'a ' is,Van9(t)= v9 sin.9mt.The ninth harmonic in phase bnwill be,Vbn9(t) = v, Sin(9(mt-1200))

= v, Sin(9mt-10800)= v, Sin9mtThe ideal waveform for sinusoidal pulse width modulationwas given below,

Fig.13 Waveform for SPWM.VII. SIMULATION, HARDWARE AND SYSTEMRESULTS.

The input to the controller is the voltage and power signalsfrom the PV panels which are analog signals. The varying dutycycles for the inverter circuit will be produced by theSinusoidal PWM method. This proposed system is used formaximizing the solar panel PV power output. Theimplementation of the MPPT controller, initially modelling andsimulation of the controller employing fuzzy logic (FL) usingthe MATLAB/Simulink was carried out. fig 14 shows thedeveloped PV model system consisting of PV array, boostconverter circuit with a fuzzy logic controller connected to aninverter and a load. The PV module considered in thesimulation is the 72W PV module. The fuzzy logic basedMPPT [8], [9] controller is simulated and compared withoutMPPT controller. The simulation is used for validating thedeveloped hardware prototype.

Fig.14 Integrated PV Panel with Fuzzy based MPPTController using MATLAB

Fig.15 Pulse for Inverter Circuit

Fig.16 Boost converter output using MATLAB

Fig.17 Inverter Phase voltage using MATLAB


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Fig.IS Inverter current waveform using MATLABFig.20 Hardware Setup for Testing the Prototype MPPTController

Fig.I9 Three phase voltage using MATLABThe hardware setup for testing the prototype MPPTcontroller is as shown in fig 20. A 20-26V DC power supply isused to replace an actual PV module for the purpose of testingthe controller. Value of the inductor (L) in is 2mH. Forswitching device we use MOSFET with diode for protection.Type of the MOSFET is IRF540N. The value of the capacitor(C) is 1000 llF and the load resistance is 2 ohm. The DC-DC

converter is controlled by the analog based PID controller. Itcalculates the solar watts generated, by reading the voltage andcurrent of solar panels through the analog device AD633.Thiscontroller compares the power with previous instant andproduce the error signal either positive or negative. TheRegulating pulse-width modulators LM3254 is sendcorresponding control signal to the converter with the help ofthese error signal. To tum off the converter accordingly theconverter duty cycle will be increased or decreased. The analogbased PID controller tries to maximize the watts output fromthe solar panel by controlling the duty cycle to keep the solarpanel operating always at its Maximum Power Point. Theconverter is operating at high frequency. The suitable regulatorswhich acts as an external source delivers the necessary powerfor controller and other peripheral devices. Solar Panel is testedwith and without MPPT system at different environmentalcondition with a resistive load of 2 ohm. It is observed that thepower extracted by peak power tracker is more than thatwithout the MPPT system.

Fig.21 PWM OutputVIII. CONCLUSION

In this paper the intelligent controI techniques for the trackingofMPP were investigated in order to improve the efficiency ofPV systems, under different temperature and irradianceconditions. The design and simulation of a fuzzy logic basedMPPT controller was proposed using MATLAB. The proposedmethod has very good performances, fast responses with noovershoot and less fluctuation in the steady state, for rapidirradiance and temperature variations. By using this PWMtechnique the harmonics will be reduced. These controllers areable to maintain very rapidly and the operating point of the PVsystems at the maximum power point hence improving theamount of energy effectively extracted from the PV modules,i.e. increasing the efficiency of the PV system.

REFERENCES[1] Azadeh Safari and Saad Mekhilef, "Simulation and HardwareImplementation of Incremetal Conductance MPPT with Direct ControlMethod Using Cuk Converter", IEEE TRANSACTIONS ONINDUSTRIAL ELECTRONICS, VOL. 58, NO.4, APRIL 2011.[2] Ahmed K.Abdelsalam, Ahmed M. Massoud, ShehabAhmed and PrasadN. Enjeti, "High-Performance Adaptive Perturb and Observe MPPTTechnique for Photovoltaic- Based Micro grids", IEEE TRANSACTIONSON POWER ELECTRONICS, VOL. 26, NO.4, APRIL 2011.[3] Ch. Hua and Ch. Shen, Comparative "Study of peak power trackingtechniques for the solar storage system", in IEEE APPLIED POWER


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IEEE-ICoAC 2012ELECTRONICSCONFERENCEAND EXPOSITION (APEC' 98), Vol.2,1998, pp.679 - 685.[4] J ian-Long Kuo, Kai -Lun Chao, and Li-Shiang Lee, "Dual MechatronicMPPT Controllers with PN and OPSO Control Algorithms for RotatableSolar Panel in PHEV System", IEEE TRANSACTIONS ONINDUSTRIAL ELECTRONICS, VOL. 57, NO.2, FEBRUARY 2010.[5] Mummadi Veerachary, Tomonobu Senjyu, and Katsumi Uezato, "Neural- Network Based Maximum Power Point Tracking of Coupled InductorInterleaved Boost Converter Supplied PV System Using FuzzyController" IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS,VOL. 50, NO.4, AUGUST 2003.[6] Nobuyoshi Mutoh, Masahiro Ohno, and Takayoshi Inoue, "AMethod for MPPT Control While searching for ParametersCorresponding to Weather Conditions for PV Generat ion Systems",IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 53,NO.4, AUGUST 2006.[7] Nicol a Femia, Giovanni Petrone, Giovann i Spagnuoloand Mass imoVitelli, "Optimization of Perturb and Observe Maximum Power PointTrackingMethod", IEEE TRANSACTIONSON POWER ELECTRONICS,VOL. 20, NO.4, JULY 2005.[8] Oscar Lopez-Lapena, Maria Teresa Penel laand Manel Gasul la, "A NewMPPT Method for Low-Power Solar Energy Harvesting", IEEETRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 57, NO.9,SEPTEMBER 2010.[9] Pallab Midya, Ken Haddad, and Matt Miller, "Buck or BoostTracking Power Converter", IEEE POWER ELECTRONICS LETTERS,VOL. 2, NO.4, DECEMBER 2004.[10] Vil lalva M G "Modell ing and circuit-based simulat ion of photovoltaicarrays", IEEE TRANSACTIONS ON POWER ELECTRONICS 2009 VOL.25, NO.5, PP. 1198 -1208.[11] Z. Salameh and Daniel Taylor, Step-up maximum power point t rackerfor photovoltaic arrays, Solar Energy, Vol. 44, n 1, 1990, pp. 57-61.

ACKNOWLEDGEMENTMr. S. Vasantharaj has received the Bachelor degreein Electrical and Electronics Engineering from M.Kumarasamy Col lege of Engineering, AnnaUnivers ity, India in 2008. He has worked one yearfor Gulfmax International LLC, Dubai and one yearfor LMD Electricals and Engineering works, India inElectrical Maintenance. He is pursuing Master ofEngineering in Power Electronics and Drives fromJeppiaar Engineering College, Anna University,India.Prof. Dr.M.Sasikumar has received the Bachelordegree in Electr ica l and Elect ronics Engineeringfrom K.S .Rangasamy College of Technology,Madras Univers ity , India in 1999, and the M.Techdegree in power electronics from VIT University, in2006. He has obtained his Ph.D. degree fromSathyabama Univers ity , Chennai. Cur rent ly he isworking as a Professor and Head in JeppiaarEngineering College, Chennai Tamilnadu, India. Hehas pub lis hed papers in Na tional, Internationalconferences and journals in the field of powerelectronics and wind energy conversion systems. His area of interest includes inthe fields of wind energy sys tems and power converter with soft swi tching

PWM schemes. He is a life member ofISTE.

an artifical intelligent controller for 3 phase inverter based solar pv system using boost converter

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