Abstract-This paper focuses on a Matlab/SIMULINK model of a photovoltaic cell. This model is based on mathematical equations and is described through an equivalent circuit including a photocurrent source, a diode, a series resistor and a shunt resistor. The developed model allows the prediction of PV cell behaviour under different physical and environmental parameters. The model can also be used to extract the physical parameters for a given solar PV cell as a function of temperature and solar radiation. In addition, this study outlines the working principle of PV module as well as PV array. In order to validate the developed model, an experimental test bench was built and the obtained results exhibited a good agreement with the simulation ones. Keywords-Matlab, SIMULINK, PV, solar cell model, solar array model, solar radiation, maximum power point
1. Introduction The development of new energy sources is continuously enhanced because of the critical situation of the chemical industrial fuels such as oil, gas and others. Thus, the renewable energy sources have become a more important contributor to the total energy consumed in the world. In fact, the demand for solar energy has increased by 20% to 25% over the past 20 years [1]. The market for PV systems is growing worldwide. In fact, nowadays, solar PV provides around 4800 GW. Between 2004 and 2009, grid connected PV capacity reached 21 GW and was increasing at an annual average rate of 60% [2]. In order to get benefit from the application of PV systems, research activities are being conducted in an attempt to gain further improvement in their cost, efficiency and reliability. With no pollutant emission, Photovoltaic cells convert sunlight directly to electricity. They are basically made up of a PN junction. Figure 1 shows the photocurrent generation principle of PV cells. In fact, when sunlight hits the cell, the photons are absorbed by the semiconductor atoms, freeing electrons from the negative layer. This free electron finds its path through an external circuit toward the positive layer resulting in an electric current from the positive layer to the negative one.
The Term Paper on Detailed Information On Solar Energy
The sun is the source of all life on earth. Thanks to the sun, there is light, warmth and food on the earth. Many kinds of energy on earth originate from and through solar radiation. Since the sun doesn’t have the same strength at all places and all times, the earth is warmed up unequally. This causes wind which can be converted into electricity by means of wind turbines. By evaporation we ...
Fig.1.Photocurrent generation principle. Typically, a PV cell generates a voltage around 0.5 to 0.8 volts depending on the semiconductor and the built-up technology. This voltage is low enough as it cannot be of use. Therefore, to get benefit from this technology, tens of PV cells (involving 36 to 72 cells) are connected in series to form a PV module. These modules can be interconnected in series and/or parallel to form a PV panel. In case these modules are connected in series, their voltages are added with the same current. Nevertheless, when they are connected in parallel, their currents are added while the voltage is the same. Three major families of PV cells are monocrystalline technology, polycrystalline technology and thin film
INTERNATIONAL JOURNAL of RENEWABLE ENERGY RESEARCH Tarak Salmi et al., Vol.2, No.2, 2012 technologies. The monocrystalline and polycrystalline technologies are based on microelectronic manufacturing technology and their efficiency is in general between 10% and 15% for monocrystalline and between 9% and 12% for polycrystalline. For thin film cells, the efficiency is 10% for a-Si, 12% for CuInSe2 and 9% for CdTe [3]. Thus, the monocrystalline cell that has the highest efficiency is the focus of this paper. This paper carried out a Matlab/SIMULINK model of monocrystalline PV cell that made possible the prediction of the PV cell behaviour under different varying parameters such as solar radiation, ambient temperature, series resistor, shunt resistor, diode saturation current, etc. The focus of this paper is on solar cell modelling which is discussed in section two. Section three presents the effects of the variation of the solar radiation. In section four, the influence of temperature on the PV cell outputs are investigated. The effects of the series resistance have been presented in section five. Section six focuses on the effects of the shunt resistance. In section seven, the effects of the diode reverse saturation current are studied. The model features and its experimental validation are discussed in sections eight through ten. While conclusions and future works are presented in section eleven. 2. PV cell model Fig. 4.I-V curves and P-V curves for a given PV cell 3. Effects of Solar Radiation Variation and Rsh, the I-V and P-V curves are generated as shown in Fig.4.
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Introduction My neighbor Cindy is asking my advice about her new idea of running a contracting business for the installation of solar panels. She is interested about the cost savings that households and business can take advantage of as a competitive advantage to promote the investment. In addition, she thinks that consumers will be willing to invest in solar panel services due to the reality that ...
Fig. 3. PV cell Matlab/SIMULINK model.
The equivalent circuit of a PV cell is shown in Fig. 2. It includes a current source, a diode, a series resistance and a shunt resistance [4, 5].
The above model includes two subsystems: one that calculates the PV cell photocurrent which depends on the radiation and the temperature according to equation (2) [3].
I ph I sc K i T 298 1000
(2)
where Ki=0.0017 A/◦C is the cell’s short circuit current temperature coefficient and β is the solar radiation (W/m2).
Fig. 2.PV cell equivalent circuit. In view of that, the current to the load can be given as: [6,7,8] Based on the above equation, the subsystem of Fig. 5 is obtained and the model simulation results are shown in Figs. 6 and 7.
q V Rs I V Rs I I I ph I s exp 1 NKT Rsh
(1)
In this equation, Iph is the photocurrent, Is is the reverse saturation current of the diode, q is the electron charge, V is the voltage across the diode, K is the Boltzmann’s constant, T is the junction temperature, N is the ideality factor of the diode, and Rs and Rsh are the series and shunt resistors of the cell, respectively. As a result, the complete physical behaviour of the PV cell is in relation with Iph, Is, Rs and Rsh from one hand and with two environmental parameters as the temperature and the solar radiation from the other hand. Based on equation (1), the Matlab/SIMULINK model of Fig.3 was developed. For a given radiation, temperature, Rs
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Fig. 5. Iph Matlab/SIMULINK subsystem for varying cell temperature and solar radiation. As it can be seen from Figs.6 and 7, the PV cell current is strongly dependent on the solar radiation. However, the 214
INTERNATIONAL JOURNAL of RENEWABLE ENERGY RESEARCH Tarak Salmi et al., Vol.2, No.2, 2012 voltage has a 50 mV increase as the solar radiation increased from 400 W/m2 to 1000 W/m2. In general, for a given solar radiation, when the cell temperature increases, the open circuit voltage Voc, drops slightly, while the short circuit current increases. This behaviour is validated and presented in Figs. 9 and 10.
Fig.6.I-V curves for different solar radiations. Fig.9.I-V curves for different cell temperatures.
Fig.7.P-V curves for different solar radiations. 4. Effect of Varying Cell Temperature 5. Fig.10.P-V curves for different cell temperatures. Effect of Varying Rs
The diode reverse saturation current varies as a cubic function of the temperature and it can be expressed as:
T I s T I s T nom
3 E exp T 1 g N .V Tnom t
(3)
where Is is the diode reverse saturation current, Tnom is the nominal temperature, Eg is the band gap energy of the semiconductor and Vt is the thermal voltage. The reverse saturation current subsystem shown in Fig.8 was constructed based on equation (3).
The series resistance of the PV cell is low, and in some cases, it can be neglected [3]. However, to render the model suitable for any given PV cell, it is possible to vary this resistance and predict the influence of its variation on the PV cell outputs. As seen in Figs.11 and 12, the variation of Rs affects the slope angle of the I-V curves resulting in a deviation of the maximum power point.
Fig.11.I-V curves for different Rs.
Fig. 8. Matlab/SIMULINK temperature effect subsystem on diode reverse saturation current.
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INTERNATIONAL JOURNAL of RENEWABLE ENERGY RESEARCH Tarak Salmi et al., Vol.2, No.2, 2012 7. Effects of Varying Is.
The model assists in expecting the behaviour of the PV cell for different reverse saturation currents of the diode. The curves of Figs.15 and 16 were plotted for three different values of Is: 100nA, 10nA and 1nA. The influence of an increase in Is is evidently seen as decreasing the open-circuit voltage Voc. 8. Fig.12.P-V curves for different Rs The simulation was performed for three different values of Rs, namely 1mΩ, 4mΩ and 8mΩ. It was shown that higher values of Rs reduce the power output of the PV cell. According to equation (4), the fill factor, given by equation (4), decreases as Rs increases. PV Module
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INTRODUCTION “Because we are now running out of gas and oil, we must prepare quickly for a third change, to strict conservation and to the use of coal and permanent renewable energy sources, like solar power.” – JIMMY CARTER, televised speech, Apr. 18, 1977 In times such as today, cumulative solar energy production accounts for less than 0.01% of total Global Primary Energy demand. And the ...
As previously mentioned, a PV module is a connection of tens of PV cells. Figure 17 shows the bloc diagram of Matlab/SIMULINK model of a PV module. This model contains an external control block permitting an uncomplicated variation of the models’ parameters. In this model, 36 PV cell are interconnected in series to form one module. As a result, the module voltage is obtained by multiplying the cell voltage by the cells number while the total module current is the same as the cell’s one. The results are shown in Figs.18 and 19.
FF
Pmax Voc I sc
(4)
6.
Effect of Varying Rsh
The shunt resistance of any PV cell should be large enough for higher output power and fill factor. In fact, for a low shunt resistor, the PV cell current collapses more steeply which means higher power loss and lower fill factor. These results can be seen in Figs.13 and 14.
Fig.15.I-V curves for different Is
Fig.13.I-V characteristics for different Rsh
Fig.16.P-V curves for different Is
Fig.14.P-V curves for different Rsh
Fig.17. SIMULINK model for the PV module. 216
INTERNATIONAL JOURNAL of RENEWABLE ENERGY RESEARCH Tarak Salmi et al., Vol.2, No.2, 2012
Fig.18.I-V curves of the PV module model
Fig.21.I-V curves for the PV array model
Fig.19.P-V curves of the PV module model 9. PV Array
Fig.22.P-V curves for the PV array model 10. Experimental Results and Validation In order to validate the Matlab/SIMULINK model, The PV test bench of Fig.23 was investigated. It consists of a rheostat, a daystar-meter to measure the solar radiation, two digital multi-meters and a solar panel that has the key specifications listed in Table 1.
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In order to get benefit from these developed models, an array of 6 PV modules has been constructed. In fact, these PV modules were interconnected in series and all of them are connected to the external control block as shown in Fig.20.
Fig.20. PV array model. The PV array model was simulated similarly to the model of the PV module and the obtained results are shown in Figs.21 and 22, respectively. Fig. 23. Setup of the PVL-124 solar laminate panel.
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INTERNATIONAL JOURNAL of RENEWABLE ENERGY RESEARCH Tarak Salmi et al., Vol.2, No.2, 2012 Table 1. Electrical specifications for the test panel Solar Laminate PVL-Series Model: PVL-124 Maximum power 124 W Voltage at Pmax 30 V Current at Pmax 4.1 A Open circuit voltage 42 V Short circuit current 5.1 A The Matlab/SIMULINK model was evaluated for the PVL-124 solar panel. The results are shown in Fig.24. On the other hand, the experimental results for a solar radiation of 540 W/m2 are shown in Fig. 25. The I-V and P-V simulation and experimental results show a good agreement in terms of short circuit current, open circuit voltage and maximum power. In this study, the Matlab/SIMULINK model not only helps to predict the behavior of any PV cell under different physical and environmental conditions, also it can be considered a smart tool to extract the internal parameters of any solar PV cell including the ideal factor, series and shunt resistance. Some of these parameters are not always provided by the manufactures. 11. Conclusion A Matlab/SIMULINK model for the solar PV cell, modules and array was developed and presented in this paper. This model is based on the fundamental circuit equations of a solar PV cell taking into account the effects of physical and environmental parameters such as the solar radiation and cell temperature. The module model was simulated and validated experimentally using the high efficient PVL-124 solar laminate panel. As a result of the study, one can benefit from this model as a photovoltaic generator in the framework of the SimPower-System Matlab/SIMULINK toolbox in the field of solar PV power conversion systems. In addition, such a model would provide a tool to predict the behaviour of any solar PV cell, module and array under climate and physical parameters changes.
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When we have a job that we love, we want to keep it no matter what. That’s understandable, but we have to be careful how far we actually go in order to keep it. There are things much more important than any job in the world like our health. Even for those who’s jobs, looks are everything. We all want to look our best at all time, especially if we are in the modeling business. There have been many ...
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Fig. 25.PVL-124 solar laminate panel experimental results. References [1] Jeyraj Selvaraj, Nasrudin A. Rahim, “Multilevel Inverter For Grid-Connected PV System Employing Digital PI Controller”, IEEE Transactions On Industrial Electronics, vol. 56, No. 1, pp. 149-158 , 2009. [2] Renewable Energy Policy Network for the 21st Century (REN21), “Renewable 2010 Global Status Report”, Deutsche Gesellschaftfür Technische Zusammenarbeit (GTZ) GmbH, pp. 19, 2010. [3] Savita Nema, R.K. Nema, Gayatri Agnihotri, “MATLAB/Simulink based study of photovoltaic cells / modules / array and their experimental verification”, International journal of Energy and Environment, vol.1, No.3, pp.487-500, 2010. [4] Huan-Liang Tsai, Ci-Siang Tu, Yi-Jie Su, “Development of Generalized Photovoltaic Model Using MATLAB/SIMULINK”, Proceedings of the World Congress on Engineering and Computer Science WCECS, San Francisco, USA, 2008. [5] Francisco M, González-Longatt, “Model of Photovoltaic Module in Matlab™”, 2do congresoı beroamerı cano de estudıantes de ıngenıeríaeléctrı ca, electrónıca y computacıón pp.1-5, 2005. [6] S. Rustemli, F. Dincer, “Modeling of Photovoltaic Panel and Examining Effects of Temperature in Matlab/Simulink”, Electronics and Electrical Engineering, ISSN 1392-1215, no. 3(109), pp. 35-40, 2011. [7] Kinal Kachhiya, Makarand Lokhande, Mukesh Patel, “MATLAB/Simulink Model of Solar PV Module and MPPT Algorithm”, Proceedings of the National Conference on Recent Trends in Engineering and Technology, 2011. [8] I.H. Atlas, A.M. Sharaf, “A Photovoltaic Array Simulation Model for Matlab-Simulink GUI Environment”, International Conference on Clean Power, pp. 341-345, 2007.
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