Modeling and simulation of photovoltaic arrays

Authors:Eng. Ioan‐Viorel BANU, PhD studentProf. Eng. Marcel ISTRATE, PhD

„Gheorghe Asachi” Technical University of Iaşi

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Among of the systems which use renewable energy sources,photovoltaic cells are promising, because of the intrinsicqualities of the system itself: very low exploitation costs (freefuel), limited maintenance requirements, reliable, silent and easyto install.Usually the solar cells are modeled using a specific type ofequivalent circuit. Any photovoltaic model is based on diodebehavior, which gives to photovoltaic cell its exponentialcharacteristic.The method of modeling of photovoltaic arrays is performedinto MATLAB® 7.13 (2011b) using the Solar Cell block fromSimElectronics® library. The solar cell is a solar current source,which includes solar‐induced current and temperaturedependence.

INTRODUCTION

Solar‐induced current

··· 1 ·

·· 1

·

Where:Solar‐induced current;Saturation current of the first diode and second diode respectively;

, Quality factor (emission coefficient) of the first and second diode;Thermal voltage ⁄ , ( : Boltzmann constant, : device temperature);

, Series and parallel (shunt) resistance;Voltage at the terminals of the solar cell.

INTRODUCTION

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Solar cell equivalent circuit model Temperature dependence

· 1 1 ·

Where:1 First temperature coefficient for  ;

Extraction temperature parameter.

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The Simulink® model for plotting the characteristics ofphotovoltaic arrays

MODEL OF PHOTOVOLTAIC ARRAY

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Parameter ValueShort-circuit current [A] 34.7scI Open-circuit voltage [V] 6.0ocV Quality factor N = 1.5 Series resistance [Ω] 0sR First order temperature coefficient for phI [1/K]

TIPH1 = 0

Temperature exponent for sI TXIS1 = 3

Temperature exponent for sR TRS1 = 0 Parameter extraction temperature [°C]

25measT

Fixed circuit temperature [°C] TFIXED = 25

The parameters of a single solar cell

Current, voltage and power curves for PV array

MODEL OF PHOTOVOLTAIC ARRAY

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Model using test equipment dataIf experimental data and mathematical model are available, theinformation are entered in MATLAB and Simulink with tools thatallow to do curve fitting in these data points and is created athree‐dimensional surface.From this mathematical representation is create a Simulink blockwhich represents the model directly.

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Simulation of photovoltaic panel

Model using test equipment data

Solar panel V‐I source

Photovoltaic panel is modeled as a constant DC source.The Photovoltaic V‐I Curves 2D Lookup Table block has twoinputs: the irradiation and the voltage and in the output of theblock is calculated the current.The model generates a current and receives voltage back fromthe system.

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EXPERIMANTAL RESULTS

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If the irradiance decreases, thephotovoltaic current generateddecreases proportionally to that, andvariation of no‐load voltage is verysmall.When the temperature of moduleincreases the voltage decreases andthe produced current remainspractically constant.For an irradiance of 600 ⁄ isobtained a maximum power of 70and for an irradiation of 800 ⁄the photovoltaic panel can provide amaximum power of 96 .

Results of the simulation ofphotovoltaic panel

Variation of solar radiation

EXPERIMANTAL RESULTS

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This paper analyzed the implementation of a method formodeling in MATLAB®/Simulink® of photovoltaic arrays andmodeling using experimental data for create a photovoltaic arraysimulator.To build photovoltaic panel was used the Solar Cell block, and toimplement the fixed predictive model for use as a source for aphotovoltaic system was used Curve Fitting Tools.The implemented model was validated through simulation.The simulation results show that the proposed method isefficient in terms of modeling of the functioning of thephotovoltaic system.

CONCLUSIONS

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THANK YOU!