A PHOTOVOLTAIC PANEL MODEL IN MATLAB/SIMULINKShivananda Pukhrem* *[email protected],[email protected] Faculty of Electrical Engineering Program: Renewable Energy System Wroclaw University of Technology, 27 Wybrzeże Wyspiańskiego St., 50-370 Wrocław, Poland Abstract— A circuit based simulation model for a PV cell for estimating the IV characteristic curves of photovoltaic panel with respect to changes on environmental parameters (temperature and irradiance) and cell parameters (parasitic resistance and ideality factor).This paper could be used to analyze in the development of MPPT (maximum power point tracking) algorithm. Using a Shockley diode equation, an accurate simulink PV panel model is developed. 60W Solarex MSX60 PV panel is chosen for evaluating the developed model. Index Terms—Photovoltaic (PV), Shockley diode, irradiance, Matlab/Simulink, IV and PV curves and MPPT. I. Introduction Renewable energy resources have become a hot topic for the past two decades. Many research institutions have dedicated their time to harness the optimum power from it [1]. In case of PV plant, the optimum efficiency is affected mainly by three factors: the efficiency of the PV panel (in commercial PV panels it is between 8-15 %[2]), the efficiency of the inverter (9598%[3]) and the efficiency of the maximum power point tracking (MPPT) algorithm (which is over 98%[4]).Improving the efficiency of panels and inverter is not easy as it depends on the technology availability and expenses, however improving the MPPT algorithm is an inexpensive way. This paper allows a researcher to develop a better MPPT algorithm by understanding the PV panel behavior under different conditions (environmental as well as the cell parameters). II. The Physics of Photovoltaic cell A simple solar cell consist of solid state p-n junction fabricated from a semiconductor material (usually silicon).In dark, the IV characteristic of a solar cell has an exponential characteristic similar to that of a diode[5]. However when the solar energy (photons) hits on the solar cell, energy greater than the band gap energy of the semiconductor, and release electrons from the atoms in the semiconductor material, creating electron-hole pairs [6].The charged carrier are moved apart under the influence of internal electric fields of the p-n junction and hence a current proportional to the incident photon radiation is developed. This phenomenon is called photovoltaic effect, first observed by A.E Becquerel in 1839[7].When the cell is short circuited, this current flows in the external circuit but when open circuited, this current is shunted internally by the intrinsic p-n junction diode. In this paper, a variable load is connected in the external short circuit. The complete model is available in [8]. A. A PV cell model A simplest equivalent circuit of a solar cell is a current source in parallel with a diode. The output of the current source is directly Temperature dependence photo current Iph. the load characteristic is a straight line with slope . Fig: 1 Circuit diagram of a PV cell [6]. IV curve for a PV cell the Equations which define the model of a PV cell are given below [9]. 3. in parallel with the diode. In some cases if the R . of Fig: 2 Characteristic of IV curve from Iph and Id[11]. the solar cell is not an active device. However. it works as a diode. if it is allowed to connect to an external source (large voltage) it generates a current Id. The net current I is obtained from the photo current Iph and the diode current Id [11]. During darkness. (5) 6.Accurate simulation is obtained after considering the following parameters: Temperature dependence of the diode reserved saturation current Is. this corresponds to the leakage current to the ground. [10]: 1. i. (2) Fig: 3 Current-Voltage (IV) curve for a PV cell[6]. Power delivered to the load depends on the value of the resistance only. It produces neither a current nor a voltage. (7) 8. Shunt resistance Rsh [9]. A general I-V characteristic of the solar cell for a given ambient irradiation ‘G’ and fixed cell temperature ‘T’ is shown in Fig 3. a p-n junction. called diode (D) current or dark current. Nomenclature from page-6 for the (1)-(8) equations variables. Series resistance Rs [9] (internal losses due to the current flow) which gives a more accurate shape between the maximum power point and the open circuit voltage. (6) 7. B.For a certain resistive load. The diode determines the IV characteristics of the cell. The circuit diagram of a PV cell is shown above in Fig 1. (1) 2. (3) 4. (4) 5. Fig 2 shows the characteristic of IV curve.proportional to the solar energy (photons) that hits on the solar cell (photocurrent Iph). (8) Used V.e. r. which is the change in panel per ºC at temperatures other than 25°C. Environmental parameters (temperature and irradiance): The influence of the cell temperature T and the ambient irradiation G on the cell characteristics can be obtained from the model equations. which is almost equivalent to a short circuit current. the PV cell act as a constant current source. Short circuit current: = (Greatest value of the current generated by a PV cell. where is the ambient irradiation and A is the PV cell area. = 25ºC) = from (7) which is the greatest current. 3.A PV cell is characterized by the following fundamental parameters w. Cell parameters (parasitic resistance and ideality factor): Resistive effects in solar cells reduce the efficiency of the solar cell by dissipating power in the resistances. hence making the PV cell less efficient. From (7) as G increases the increases but from (2) as the increases the decreases. The prominent effect with increasing the PV cell’s temperature is the linear decrease of the open circuit voltage. However FF decreases as the cell temperature increases. since = 25ºC for all test conditions. if the R load is large. Maximum power point is the operating point in Fig 3. in (7) is greater when changes from (=25°C). which is produced by the short circuit condition: V=0. 5.t Fig3 1.5. the PV cell operates in the M-N region of the IV curve (Fig3). the PV cell operates in the P-S region of the IV curve. From equation (7) photo current (A) is a function of the ambient irradiation G (W/ ) and from equation (2) cell temperature (K) is linear decrease of the .It presumes the voltage of the PV cell in the night and it is expressed by (2). Fill factor (FF) is the ratio of the maximum power that can be delivered to the load and the theoretical maximum power which is the product of and . Open circuit voltage is a voltage drop across the diode D when the generated current I=0. G= 1 kW/m at spectral distribution of AM =1. Influence of . However. the PV cell act as a constant voltage source almost equivalent to the open circuit voltage [9]. Both the magnitude and impact of series and shunt resistance depends 2. Consideration of environmental parameters and cell parameters in PV cell model i. The short circuit current slightly increases with the cell temperature. Maximum efficiency is the ratio of the maximum power and the incident solar energy (photons).7 for a good PV cell. The most common parasitic resistances are series resistance and shunt resistance whose key impact is to reduce the fill factor. At STC (Standard Test Condition. current is a linear function of the ambient irradiation.where the power dissipated in the resistive load is maximum: 4.load is very small.FF is a measure of real I-V characteristic which value much be higher than 0. The open circuit voltage increases logarithmically with the ambient irradiation where as the short circuit . C. ii. Series resistance in a solar cell has three causes: the movement of current through the emitter and base of the solar cell. D. rather than poor solar cell design. not in the junction). and [10].Fig:4 depicts the PV cell simulation set up in general. The ideality factor n of a diode is a measure of how closely the diode follows the ideal diode equation. An estimate for the value of the of a solar cell can be determined from the slope of the IV curve near the point [12].2 . the contact resistance between the metal contact and the silicon. Significant power losses caused by the presence of a shunt resistance are typically due to manufacturing defects.However recombination does occur in other ways and in other areas of the device.1 Also some calculated data for Solarex MSX60[13] which is important for evaluating with simulated model is shown in Table.e. A straight forward method of estimating the series resistance from a solar cell is to find the slope of the IV curve at the point [12]. and n different results are obtained.For an ideal condition (ideal diode characteristic). Fig: 4 A PV cell simulation set up After changing . (1. It is measured in Ω . at the operating point of the solar cell.on the geometry of the solar cell. 2) is developed in MATLAB/SIMLINK with a variable load resistance at the output. and the resistance of the top and rear metal contacts. some predefined specification are obtained for Solarex MSX-60 from [13] and is shown in Table. This recombination’s produce ideality factors n that deviate from the ideal [12]. The ideal diode equation assumes that all the recombination occurs via band to band or recombination via traps in the bulk areas from the device (i. Prior to simulation. A PV cell simulation set up Considering the environmental and cell parameters. a PV cell simulation set up model based on equations (1)-(8) and Tables. 5 Current A Current A 3 2 2 1. Under STC with Rs=0.5 2 1.5 1.3 can be compared with Table. parasitic series resistor(Rs) 4 Rs=0 ohm Rs=0.5 3 2.90 3.5 4 0 5 10 15 20 0 5 10 15 20 25 Volatge V 25 Volatge V Fig: 8 IV curves at different Fig: 5 IV curves at different G Fig: 9 shows the IV curves at different under STC with =0.54 n=1.5 1 1 0.5 2 1.18 ohm Rp=360 ohm and at different n Under G=1000 W/sq.5 0 0 5 10 15 Volatge V Fig: 9 IV curves at different n 20 25 .5 0 0 Rp=5 ohm Rp=10 ohm Rp=50 ohm Rp=360 ohm Rp=1000 ohm 3.36 n=1. Table.5 3 G=400 W/m2 G=200 W/m2 Current A 2.3 shows the calculated data from the simulated model [8] at STC.18 ohm.5 0 0 5 10 15 20 Volatge V Fig: 6 IV curves at different Top 25 n=1. Simulation results Fig: 7 shows the IV curves at different under STC with =360 ohm.5 1.18 ohm and =360 ohm.18 n=1.m and different Top 4 4 Top=0°C Top=25°C Top=50°C Top=75°C Top=100°C 3.5.5 0 0 5 10 15 20 25 Volatge V Fig: 7 IV curves at different Fig: 8 shows the IV curves at different under STC with =0. Fig: 6 shows the IV curves at different (ºC) with constant G=1000 W/ and AM=1.36 ohm Rs=0.Table. parasitic shunt resistor(Rp) 4 Top=25°C and different Irradiance G=1000 W/m2 3 G=800 W/m2 3.5 Current A G=600 W/m2 2 2.72 n=1.54 ohm Rs=0. Fig: 5 shows the IV curves at different irradiance G (W/ ) with constant =25ºC and AM=1.5 0.III.5 1 0.72 ohm 3.5 2.5 1 1 0.18 ohm Rs=0.5 0.5 Current A 3 2.5. Under STC with Rp=360 ohm and diff. Under STC with Rp=360 ohm and diff.1 for evalating the simulation results. org [2] “Trends in photovoltaic applications. Fernandez Gamiz. 4.5. 36 : No of PV panel in series & parallel : Band-gap energy of the cell. 1. Vol.mathworks. March 2013 [14] http://californiasolarcenter. Zamora. 1. Mar. vol.J. Hence this paper is a summary for understanding the behavior of PV panel with change of the said variables and also in estimating the IV curves under such changes.org/wiki/A. and n=1.49-56.2010 [4] L. no. [5] G.wikipedia.36 C: No of cells in a PV panel.M=1. 2010 [3] “Sunny Family 2010/2011 . the variables .6e-19 C : Diode reversed saturation current.org/ssh. vol. no.Solar Electricity Engineering of Photovoltaic Systems. R. Nomenclature STC: Standard Test Condition. =0. International Energy Agency.21. 3. 5.Donatien Njomo. Iss. 2001. S." Renewable Power Generation.pveducation. IET._E. Walker.38e-23 : Cell operating temperature in ºC : Cell temperature at 25ºC : Electron Charge constant. “Two photovoltaic cell simulation models in Matlab/Simulink ”(IJTPE). This ideal condition is also specified in the Solarex MSX-60 datasheet [14]. Zulueta .Every manufacture intends to produce their PV panel in the ideal condition as mentioned above.3 Vol. Conclusion VI. vol. "Evaluating MPPT converter topologies using a MATLAB PV model. Iss. pp.1. A V: Output voltage from the PV panel. Motrico . “Comprehensive Approach to Modeling and Simulation of Photovoltaic Arrays” -IEEE Transactions on power electronics. Rizzo. [1] Sustainable Energy for All http://www.O. 2012 [11] Marcelo Gradella Villalva. References From the simulation results which are depicted in figures (5)-(9). Zacharie Koalaga. these results could be used to develop the MPPT algorithm by understanding how these variables work. Ramos-Hernanz. [7] https://en.12eV A.2do congreso iberoamericano de estudiantes de ingeniería eléctrica.M= Air mass coefficient [15] at spectral . Piegari. Australia. July 2010.18 ohm. “Modeling and Simulation of photovoltaic module considering single-diode equivalent circuit model in MATLAB”. .org/pvcdrom/solar-celloperation/ [13] Dominique Bonkoungou. . E. In addition to it. [10] J.J. V. I.com/matlabcentral/fileexch ange/41537-a-photovoltaic-panel-model-inmatlabsimulink [9] Francisco M. Artes Graficas Gala. Larranaga .J. May 2009 [12] http://www. A : Shunt current. electrónica y computación. 4. G= 1kW/ distribution of AM=1. [6] Lorenzo.org/wiki/Air mass(solar_energy) . 4.5 =25ºC : Solar irradiance ratio = : Thermal Voltage. The ideal condition for obtaining the maximum power from the PV panel are =25ºC. Barambones . and n which affects the performance of a PV panel is studied thoroughly. 24.(IJETAE).wikipedia.” Journal of Electrical & Electronics Engineering.sustainableenergyforall.html/newssh/pd fs/Solarex-MSX64. 1. 1.the Future of Solar Technology”.. No. V : Boltzmann’s constant. and Ernesto Ruppert Filho. 1. Spain. No. Report IEAPVPS Task 1 T1-19:2010. A : Diode reversed saturation current at I: Output current from the PV panel.L.J. (1994). V n: Diode ideality factor.pdf [15] http://en. González-Longat . 317-328. Campayo .A.U. "Adaptive perturb and observe algorithm for photovoltaic maximum power point tracking._Becquerel [8] http://www. Survey report of selected IEA countries between 1992 and 2009”.IV. pp. 10.36 which is shown in Fig: 5 with legend G=1000 W/ (blue color).IEAust. A. “Model of Photovoltaic Module in Matlab” (II CIBELEC 2005). Jonas Rafael Gazoli. E.SMA product catalogue.
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