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Modeling Solar Photovoltaic Cell and Simulated Performance Analysis of a 250W PV Module Md. Aminul Islam, Graduate Student Member, IEEE, Adel Merabet, Member, IEEE, Rachid Beguenane and Hussein Ibrahim
Abstract--The main purpose of this study is to develop the mathematical model of solar photovoltaic (PV) cell and to simulate its behavior. The study includes the performance analysis of a 250W PV module and its behavior on different temperature conditions, irradiance levels. It also focuses on the effects of varying shunt and series resistances. The model has been developed considering possible environmental effects on solar PV generation. The results of the characteristics curves in this paper are compared to the curves provided by the CS6P250M PV module datasheet. Using this model it is possible to simulate the behavior of any large scale PV array or solar Photovoltaic Energy Conversion Systems (PVECS). The model was developed by using Matlab®/Simulink® software. This model can be used for further simulation based research and analysis on PVECS. Index Terms—mathematical model; photovoltaic cell; PV module; simulation; solar irradiance; temperature
I. NOMENCLATURE Β I IPH IRS IS ISC K Ki N P PV q RS RSH STC T Tref V VOC Vt
Solar irradiation (W/m2) Load current (A) Photocurrent (A) Diode reverse saturation current (A) Diode saturation current (A) Short circuit current (A) Boltzmann’s constant (1.38 x 10-23 J/K) Temperature coefficient of short circuit current (A/0C) Diode ideality factor Cell generated power (W) Photovoltaic Electron charge (1.602 x 10-19 C) Series resistance (Ω) Shunt resistance (Ω) Standard Test Condition Cell temperature (K) Reference temperature (K) Cell terminal voltage (V) Open circuit voltage (V) Thermal voltage (V)
This work was supported by the Faculty of Graduate Studies and Research, Saint Mary’s University. M. A. Islam is with the Division of Engineering, Saint Mary’s University, Halifax, NS B3H3C3 Canada (e-mail:
[email protected]). A. Merabet is with the Division of Engineering, Saint Mary’s University, Halifax, NS B3H3C3 Canada (e-mail:
[email protected]). R. Beguenane is with the Department of Electrical and Computer Engineering, Royal Military College, Kingston, ON Canada H. Ibrahim is with Wind Energy Techno-Center, Gaspe, QC Canada 2013 IEEE Electrical Power & Energy Conferenc (EPEC) 978-1-4799-0106-7/13/$31.00 ©2013 IEEE
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II. INTRODUCTION
OSSIL fuels are playing a major role to meet the increasing growth on energy demand. At the same time it is responsible for many environmental hazards like carbon emissions and global warming. The concept of using renewable energy sources emerged from the need to search for alternate green sources of energy. In order to diminish the greenhouse effect and slow the depletion of fossil fuel, the solar energy has been developed [1]. Photovoltaic (PV) power systems are becoming increasingly important in modern electrical grids. In recent years, PV power systems have drawn significant research attention in modeling and simulation studies for stand-alone and grid-tied systems [2]. Simulation based implementation is being widely popular in research, especially for large scale analysis. PV module is the basic building block to construct the PV systems. The conventional technique to model the solar cell is to establish the mathematical expression based on the equivalent circuits of the cell [3]. A solar cell consists of layers of semiconductor materials that exploit the photoelectric effect to convert the photon energy of the sun radiation into electricity. In terms of power electronics the solar cell can be considered as a current source that exhibits non-linear characteristics [4].
This paper presents a mathematical model of solar PV cell based on an equivalent circuit [5]-[6]. It was applied to develop a 250W PV module in order to simulate its behavior. The results were compared to the original characteristics curves from the datasheet of the CS6P-250M module. This model can generate the I-V and P-V characteristics of the PC cell and module. The model is designed to study different parameters variations effect on the output of PV module. Matlab®/Simulink® software is used to develop this model, simulate and to obtain the results. Section III describes the mathematical model and simulation results of the PV cell. Section IV describes the development of the PV module based on the CS6P-250M datasheet and its basic characteristics curves. Section V focuses on the effects on solar irradiance variation on the module. Section VI analyses the effects of temperature variation on the module. The effects of varying series and shunt resistances are described in section VII and VIII respectively. Conclusions of the study are stated in section IX. III. MODELING PV CELL The equivalent circuit of a solar photovoltaic (PV) cell is
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given in the following figure. It includes a current source, a diode, a shunt resistance and a series resistancce [7].
Fig. 1. Equivalent circuit of a solar ccell
An equation of current to the load can be obtained from the equivalent circuit in Fig. 1. The load current equation is given below [8]-[10]: 1
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In this equation, I is the load currrent, IPH is the photocurrent, IS is the diode saturation currentt, q is the electron charge, V is the terminal voltage of the celll, N is the diode ideality factor, K is the Boltzmann constaant, T is the cell temperature, RS and RSH is the series and shunt resistance respectively. So, the behavior of a solar photoovoltaic (PV) cell is completely dependent on these parameters..
ulated PV cell Fig. 4. P-V curve of simu
bsystem for solar PV cell. Fig. 2 shows the Simulink® sub Generated output results in I-V and P-V characteristics curves y. are given in Fig. 3 and 4 respectively IV. MODELING PV MODULE In order to develop the model of a 250W solar photovoltaic P-250M manufactured by module a real PV module CS6P Canadian Solar has been considered as a standard module. n the available information The model was developed based on from the datasheet. Following table shows the key specification of the PV module under Standard Test Conditions (STC) [11]. TABLE I
Key Specification of CS6P-250M M PV Module under STC Electrical Characteristics Nominal Maximum Power Optimum Operating Voltage Optimum Operating Current Open Circuit Voltage, VOC Short Circuit Current, ISC Temperature Coefficient of ISC, Ki Fig. 2. Simulation model subsystem of solaar PV cell
CS6P-250M 250W 30.4V 8.22A 37.5V 8.74A 0.005A/0C
The original PV module containss total 60 cells. In order to generate the specified voltage from the simulated model, total 60 cells are required to be connected in series. In this system, desired voltage level is achieved by applying a gain on the cell t cells, to develop the voltage, equals to the number of total model of a 250W PV module.
Fig. 3. I-V curve of simulated PV ceell Fig. 5. I-V characteristics of module for diffferent irradiation and temperature
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m varies as a function temperature. The output of the PV module of solar irradiance level which caan be obtained from the following equation [8]-[10]:
1000
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Here, ISC is the short circuit currrent, Ki is the temperature coefficient of short circuit current, T is the cell temperature, d B is the solar irradiation Tref is the reference temperature and in W/m2. Fig. 6. Simulation model of solar PV m module
Fig. 9. Simulation model subsystem for photocurrent
c the photocurrent. Fig. 9 shows the subsystem that calculates The simulation was performed for 1000, 800, 600 and 400 (W/m2) irradiation levels under the Standard Test Conditions (STC). Cell temperature, T was kept constant at 250C (298K).
Fig. 7. I-V curve of simulated PV moddule
Fig. 10. I-V curve of the PV module fo or different irradiance level
Fig. 8. P-V curve of simulated PV moodule
Fig. 5 shows the I-V curve of the CS6P-2250M module for different irradiation and temperature [11].. The Simulink® model of the PV module, I-V and P-V charracteristics curves from the simulation are given in Fig. 6, 7 andd 8 respectively. V. EFFECTS OF SOLAR IRRADIANCE VARIATION The above model of PV cell in Fig. 2 inncludes two major subsystems that play a great effect on thee behavior of PV module. One of them calculates the photoocurrent, IPH. The photocurrent, IPH depends on the solar irrradiance and cell
Fig. 11. P-V curve of the PV module fo or different irradiance level
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The effects of different irradiation level on I-V and P-V characteristics are presented in Fig. 10 and 11 respectively. As seen in Fig. 10 and 11, the variation of irradiation level affects widely on the current and voltage generated in PV module. According to the results; open circuit voltage, VOC drops slightly and short circuit current, ISC decreases widely with the decrement of solar irradiation, B. This behavior for different solar irradiation has been validated from the datasheet of the CS6P-250M PV module and Fig. 5 [11].
The simulation was performed for 50C (278K), 250C (298K), 450C (318K) and 650C (338K) under the Standard Test Conditions (STC). During this test solar irradiation, B was kept constant at 1000W/m2.
VI. EFFECTS OF TEMPERATURE VARIATION The other subsystem of PV cell model calculates the diode saturation current, IS. The diode saturation current varies as a cubic function of the temperature and it can be expressed as the following equation [8], [12]-[13]:
3 Fig. 14. I-V curve of the PV module for different temperature level
In this equation, IRS is the diode reverse saturation current and Vt is the thermal voltage. The cell reverse saturation current can be obtained from the equation given below [12]:
/
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Thermal voltage, Vt can be obtained from the following equation: 5
Fig. 15. P-V curve of the PV module for different temperature level
The effects of different temperature on I-V and P-V characteristics are presented on Fig. 14 and 15 respectively. According to the I-V and P-V characteristics in Fig. 14 and 15; open circuit voltage, VOC drops and short circuit current, ISC rises slightly when the temperature increases. This behavior for varying temperature has been validated from the datasheet of the CS6P-250M PV module and Fig. 5 [11]. Fig. 12. Simulation model subsystem for diode saturation current
Fig. 13. Simulation model subsystem for reverse saturation current
The subsystems showed on Fig. 12 and 13 are constructed to generate the saturation current, IS and reverse saturation current, IRS based on (3) and (4) respectively.
VII. EFFECTS OF VARYING RS Generally the typical value of series resistance of the PV cell, RS is very low. This model was developed to render the suitable model for any given PV cell so that it is possible to vary RS and observe its effects on the behavior of the PV module. This simulation was performed for three different values of RS, respectively 1mΩ, 5mΩ and 10mΩ. The simulation was performed under the standard test condition (STC), where temperature, T was kept constant at 250C (298K) and solar irradiation level, B was kept constant at 1000W/m2.
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Fig. 16. I-V characteristics of PV module for different RS
Fig. 19. P-V characteristics of PV module m for different RSH
Fig. 18 and 19 shows the effects of varying RSH on module vely. For low value of RSH I-V and P-V characteristics respectiv the output current of the PV cell dro ops so fast and it causes a high power loss. The simulation was performed for three different values of RSH, respectively 1Ω, 10Ω and 1000Ω. The effects of different RSH can be seen in following I-V and P-V dule. Variation of RSH also characteristics curve of the PV mod affects the deviation of maximum power p point of the PV cell and module as well. IX. CONCLUSSION
Fig. 17. P-V characteristics of PV module for different RS
As seen in Fig. 16 and 17, the variation of RS affects the deviation of maximum power point of the PV cell and the module as well. However, the open circuit voltage, VOC and short circuit current, ISC remains same. VIII. EFFECTS OF VARYING RSH In general, the value of the shunt resistannce, RSH of the PV cell should be large enough to achieve the maximum output from the PV module.
The paper presents a simulation n model of solar PV cell based on mathematical expression built from an equivalent circuit. The model is proposed to simulate the characteristics of solar PV cell. This model can geenerate the behavior of PV cell depending on different solar irrradiation and temperature conditions. It can be used to develop p PV modules of any rated size. In this study the PV module waas constructed based on the datasheet of CS6P-250M module. The developed model is used to simulate the energy yield to solar PV module and m the datasheet of the given simulation results are validated from module. Furthermore, the proposed d simulation model can be extended to any desired level for furtther studies and research. X. REFERENC CES [1] [2] [3]
[4]
[5]
[6] Fig. 18. I-V characteristics of PV module for ddifferent RSH
Y. Jiang, J. A. A. Qahouq and I. Battarseh, "Improved solar PV cell Matlab simulation model and comp parison," Proc. of 2010 IEEE International Symposium on Circuits an nd Systems, pp. 2770-2773, 2010. W. Xiao; F. F. Edwin, G. Spagnuollo and J. Jatskevich, "Efficient Approaches for Modeling and Simulatin ng Photovoltaic Power Systems," IEEE Journal of Photovoltaics, vol.3, no o.1, pp. 500-508, Jan. 2013. W. Shen, Y. Ding, F. H. Choo, P. Wang; W P. C. Loh and K. K. Tan, "Mathematical model of a solar modulle for energy yield simulation in photovoltaic systems," International Conference C on Power Electronics and Drive Systems, pp. 336-341, Nov. 2009. 2 M. A. Vitorino, L. V. Hartmann, A. M. N. Lima and M. B. R. Corre a, "Using the model of the solar cell for determining d the maximum power point of photovoltaic systems," European Conference on Power Electronics and Applications, pp. 1-10, Sept. 2007. M. Bouzguenda, T. Salmi, A. Gastli and A. Masmoudi, "Evaluating solar photovoltaic system performaance using MATLAB," First International Conference on Renew wable Energies and Vehicular Technology, pp. 55-59, March 2012. B. S. Manju, R. Ramaprabha and B. I. Mathur, "Modelling and control of standalone solar photovoltaic ch harging system," International
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[7] [8]
[9] [10] [11] [12]
[13]
Conference on Emerging Trends in Electrical and Computer Technology, pp. 78-81, March 2011. W. Chen, H. Shen, B. Shu, H. Qin and T. Deng, “Evaluation of performance of MPPT devices in PV systems with storage batteries,” Renewable Energy, vol.32, no.9, pp. 1611-1622, July 2007. T. Salmi, M. Bouzguenda, A. Gastli and A. Masmoudi, “Matlab/Simulink based modeling of solar photovoltaic cell,” International Journal of Renewable Energy Research, vol.2, no.2, pp. 213-218, Feb. 2012. S. Kebaili and A. Betka, “Design and simulation of stand alone photovoltaic systems,” WSEAS Transactions on Power Systems, vol.6, no.4, pp. 89-99, Oct. 2011. I. V. Banu and M. Istrate, “Modeling and simulation of photovoltaic arrays,” Buletinul AGIR, vol.3, pp. 161-166, Aug. 2012. Canadian Solar, “CS6P 240/245/250/255/260M,” CS6P-250M Datasheet, 2013. [Online]. Available: http://www.canadian-solar.com S. Said, A. Massoud, M. Benammar, and S. Ahmed. “A Matlab/Simulink based photovoltaic array model employing SimPowerSystems toolbox,” Journal of Energy and Power Engineering, vol.6, pp. 1965-1975, Dec. 2012. T. Bennett, A. Zilouchian and R. Messenger, “Photovoltaic model and converter topology considerations for MPPT purposes,” Solar Energy, vol.86, no.7, pp. 2029-2040, July 2012.
