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1. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 - 6375(Online), Volume 5, Issue 3, March (2014), pp. 91-97 © IAEME 91 ENERGY AMELIORATION AND SIMULATION IN A MATLAB/SIMULINK” ENVIRONMENT OF A PHOTOVOLTAIC GENERATOR Abraham Kanmognea* , Oumarou Hamandjodaa , Boaz Wadawaa , Jean Nganhoua . a Laboratoire d’Energétique, Ecole Nationale Supérieure Polytechnique, BP 8390 Yaoundé, Cameroun ABSTRACT The study of the influence of solar parameters in the improvement of what about photovoltaic energy is the subject of this article. Solar intensity is highest at latitude of 18.88 °. This leads to a high value of illumination hence maximizing the electric power of a photovoltaic system. The simulation of a photovoltaic system providing energy to a Telecentre in Ngaoundéré and modeled by a resistive load in Matlab/Simulink for two different configurations: One with a Maximum Power Point Tracking adapter (MPPT) and the other without MPPT showed the stability of the power delivered by a photovoltaic system with MPPT control. Keywords: Photovoltaic Generator, Maximum Power Point Tracking (MPPT), Meteorological Parameters, Electrical Power. 1. INTRODUCTION In recent years, people in developing countries are increasingly becoming aware of the important role that renewable energy can play in overcoming energy shortage and in their socio economic development. The use of solar energy is very popular due to its potential which is about 1000 W/m2 , not leaving out the fact that it’s free anda non-pollutant. Its exploitation from photovoltaic cells provides electricity to isolated locations and for different applications such as Health needs, irrigation, lighting, telecommunications, etc. The exploitation of solar energy plays an important role in information and communication technologies which is a key factor in the promotion of education and socio-economic development of a country. However, with six billion people on the planet and only about 800 million existing telephone lines, it is likely that more than half the world's population has not yet made a telephone call, has no access to the Internet  etc. In an effort to bring information and communication technologies closer to the local populations, commonly known as telecentre, the optimization of photovoltaic solar energy as their energy source INTERNATIONAL JOURNAL OF COMPUTER ENGINEERING & TECHNOLOGY (IJCET) ISSN 0976 – 6367(Print) ISSN 0976 – 6375(Online) Volume 5, Issue 3, March (2014), pp. 91-97 © IAEME: www.iaeme.com/ijcet.asp Journal Impact Factor (2014): 8.5328 (Calculated by GISI) www.jifactor.com IJCET © I A E M E
International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 - 6375(Online), Volume 5, Issue 3, March (2014), pp. 91-97 © IAEME 92 is a determining factor. In that light, our work focuses on finding the optimum orientation of solar panels during the year and the simulation of a Photovoltaic Generator with an analogue MPPT control in the "MATLAB/SIMULINK" environment, with the goal of increasing and stabilising the power output of photovoltaic systems for a better use of solar energy. Thus, this model allows us to have the point of maximum power and its stabilization. We hypothesize that the maximum photovoltaic solar power transmitted depends on solar parameters like illumination and temperature, as well as the orientation of the solar panels. The daily illumination curve is approximated by a sine function. 2. MATERIAL AND METHOD 2.1. Material The material used in the context of our work consists of a photovoltaic module, a Cuk converter, an inverter, a resistive load which symbolizes the telecentre, a computer, MATLAB Version 7.5. The Photovoltaic module used for the simulation has as reference MSX-60  with characteristics as shown in Table 1 below. Table 1: Characteristic parameters of the photovoltaic module MSX-60 Imp Vmp Pmax ISC VOC KV KI NS A Rp RS 3.5 A 17.1 V 60 W 3.8 V 21.1 V -0.12 V/K 0.0032 A/K 36 1.3 415.4 0.22 2.2. Method The determination of the sun's altitude and azimuth will permit us to calculate the solar declination so as to choose the optimum orientation of solar panels. Irrespective of the inclination, the solar panel is always facing south to allow maximum reception of radiation . While varying the angle of inclination, we calculate the monthly solar energy captured by the solar panel, then we determine the average annual luminous intensity for each angle in the region of Ngaoundéré located at latitude 7.15° in the northern hemisphere. The orientation of the panels is defined by three angles: Inclination i, which depends on the latitude of the place and declination δ and azimuth Y measured from the South. For the simulation of a photovoltaic generator, the model takes into account the meteorological parameters of the location, the characteristics of the module and the load which modelled with a resistor representing the Ngaoundéré community telecentre. 3. RESULTS AND DISCUSSION 3.1. Monthly illuminance as a function of the inclination of the photovoltaic panel The values of the monthly illumination calculated are shown in Table 2 . Table 2: Monthly illumination as a function of the angle i in Ngaoundéré. i (°C) Illumination ( KWh/m2 ) Jan Feb Marc Apri May Jun July Aug Sept Oct Novem Decem 1.3 7.47 7.31 7.04 6.71 6.45 6.27 6.23 6.34 6.56 6.87 7.19 7.42 4.58 7.66 7.47 7.13 6.72 6.52 6.34 6.31 6.40 6.56 6.91 7.30 7.59 7.15 7.79 7.55 7.17 6.71 6.47 6.36 6.34 6.39 6.54 6.93 7.38 8 10.44 7.94 7.65 7.21 6.68 6.47 6.40 6.36 6.42 6.50 6.93 7.19 7.84 13.01 8.04 7.72 7.23 6.65 6.44 6.41 6.40 6.42 6.46 6.92 7.5 7.93 18.88 8.22 7.83 7.24 6.54 6.36 6.40 6.40 6.38 6.33 6.87 7.57 8.1 24.7 8.28 7.87 7.18 6.37 6.22 6.33 6.35 6.28 6.14 6.75 6.56 7.90 The graph in figure 1, obtained from values in Table 2, shows that the illumination is maximum for i = 18.88; where i is the angle of inclination.
International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 - 6375(Online), Volume 5, Issue 3, March (2014), pp. 91-97 © IAEME 93 5 10 15 20 6.8 6.85 6.9 6.95 7 7.05 X: 4.58 Y: 6.9 X: 7.15 Y: 6.97 X: 10.45 Y: 6.96 X: 13.02 Y: 7.01 X: 18.88 Y: 7.02 X: 24.75 Y: 6.93 X: 1.3 Y: 6.83 Figure 1: Average annual illumination for inclination i 3.2. Modelling of the photovoltaic generator (PVG) Ngaoundéré, where the PVG is installed has a room temperature between 22 and 28°C, and an annual average temperature of 25°C [5, 6]. The temperature of the photovoltaic module is given by: (1) Where: Ta is the average ambient temperature of the medium in the year; Tm is the average module temperature (°C); the average illuminance corresponding to i=18.88°; ambient reference temperature which is 20°C under standard conditions; Garef: ambient reference illumination which is 800 W/m2 under standard conditions; NOCT: The operating temperature of the cell which is the temperature reached by an encapsulated module subjected to an illumination of 800 W/m². It is about 45 °C. The value of Tm is 25.2 °C and corresponds to a module in mono-crystalline silicon. The model of the photovoltaic generator is a function of its equivalent electrical circuit. Several models of the photovoltaic generator are found in literature which differs in the number of parameters involved in the calculation of the voltage and current of the photovoltaic generator. Thus, there is a model with a single diode and a model with two diodes. We used the single diode model in this study because it is the most widely used. The photovoltaic module is characterized by its equivalent circuit diagram (Figure 2) which consists of a current source which models the conversion of luminous flux into electrical energy, a shunt resistance RP representing the leakage current of the junction, a series resistor RS representing the various resistors and contacts, and a diode in parallel which models the PN junction . Figure 2: Equivalent circuit diagram of the Model  Inclination i G(KWh/m²)
International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 - 6375(Online), Volume 5, Issue 3, March (2014), pp. 91-97 © IAEME 94 The current generated by the module is given by: (2) Where: IPV is the photovoltaic current and I0 the saturation current. is the thermodynamic potential with: NS, the number of cells connected in series, K is Boltzmann's constant (1.380 × 10 -23 JK ⁻¹), q is the electron charge (1.602 × 10 -19 C), T the junction temperature, a is the idealistic constant of the diode, Rp ( ) is the resistance of the shunt characterising the junction leakage current. The photovoltaic current is given by: (3) where IPV is the photovoltaic current under standard conditions (25 °C and 1000 W/m²), ∆T=T-Tn, T and Tn are respectively the actual and the standard temperatures ( in Kelvin ), G ( W/m²) is the illuminance at the surface of the module and G n, the standard illuminance. The saturation current is given by: (4) Where Eg is the energy gap of the semiconductor (Eg = 1.12 eV for crystalline silicon at 25 °C) and I0,n, the standard saturation current: (5) ISC ,n is the nominal short-circuit current and VOC ,n, the nominal open circuit voltage. I0 can be expressed including in I0, n, the current coefficients (KI) and voltage (kV) (6) 3.3. Photovoltaic module adapted by an analog MPPT control For a photovoltaic generator to operate under optimal conditions, it must have a matching quadruple which is a DC- DC converter (chopper) booster or reducing transformer depending on the application. When the system supplies a resistive load and the external conditions change (light and temperature), the adaptation of the PV generator to the load is through this converter. The problem is to see the influence of Maximum Power Point Tracking adapter (MPPT) on the output quantities (power, voltage, current) of a photovoltaic generator when it supplies a load. The objective here is to simulate with the SIMULINK / MATLAB software, a photovoltaic system whose operation is controlled by an analog MPPT control. MPPT control used in our study is from the work of Abdelhak AZIZ . 3.3.1. Influence of resistive load on the Photovoltaic system without MPPT control Figure 3 shows the simulated output power of the PV generator without MPPT control for the conditions (G = 1000 W/m2 , T = 25 ° C and R = 50 ) .
International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 - 6375(Online), Volume 5, Issue 3, March (2014), pp. 91-97 © IAEME 95 Figure 3: Features of the simulated output power of the PV generator without MPPT 3.3.2. Influence of resistive load on the Photovoltaic system with MPPT control Figure 4 shows the simulated power with MPPT order and with the same settings as before (G = 1000 W/m2 , T = 25 °C and R = 50 ) Figure 4: Simulated power curve across the load for system with MPPT For a period of 20 ms, the MPPT control oscillates operating point around the maximum power point (MPPT) which is 19.06 W. We note an output power of the PV generator with MPPT control to be less than that of the PV generator control without MPPT control. This is normal because the adapter dissipates energy. 3.3.3. Influence of meteorological parameters (illuminance, temperature) on the output power of the PV system The variation of the solar power received by the photovoltaic generator yielded the simulated electrical values shown in Table 3. The simulated electrical Output quantities of the generator increase with the solar power received. Table 3: Electrical quantities simulated as a function of the illuminance Illuminance G (W/m2 ) Current (A) Voltage (V) Power (W) 800 0.5072 25.36 12.86 600 0.3804 19.02 7.36 400 0.2536 12.68 3.216 On the other hand, the higher the temperature of the panels, the lower the simulated output power of the photovoltaic generator. Figure 5 and Figure 6 show respectively the simulated curve of the power terminals of the load with MPPT control and without the MPPT control for 1000 W/m2 of illuminance, a temperature of 30 °C and a load of 50 . P(W) t(s) P(W) t(s)
International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 - 6375(Online), Volume 5, Issue 3, March (2014), pp. 91-97 © IAEME 96 Figure 5: Characteristics of the simulated power for the system without MPPT at T = 30°C Figure 6: Characteristics of the simulated power for the system with MPPT at T = 30 ° C The values of the simulated power across the load for the temperatures 25 °C and 30 °C of the photovoltaic generator are contained in Table 4. Table 4: Simulated electrical power as a function of temperature Temperature (°C) System configuration Simulated power (W) 25 Without MPPT 21 With MPPT 19.06 30 Without MPPT 19.38 With MPPT 18.36 The set of simulation results are those of a control system or system regulation. The expected qualities of these results are generally stability, precision and rapidity. In a simplified approach, a system is considered stable if, for a finite amplitude variation of the ordered value or a perturbation, the measure of the quantity to be mastered stabilizes to a finite value. By observing Figures 4 and 6, signals are dampened after a 20 ms response time and stabilize at power of 19.06 W and 18.36 W respectively. It can be deduced that the photovoltaic generator with MPPT control is very stable. The curves without MPPT power system (Figs. 3 and 5) and with MPPT (Figs. 4 and 6) have a gap between them of approximately 5 %, the losses are attributed to the components of the adjustment device of the load. This insignificant gap enables us to say that the system with MPPT control is accurate. This is in agreement with the theoretical prediction shown [8,9]. The response time of the figures presented above is in the order of milliseconds, while the one shown in [8,9] for fast digital systems is in the order of a few seconds . A system with MPPT control is faster. t(s) P(W) t(s) P(W)
International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 - 6375(Online), Volume 5, Issue 3, March (2014), pp. 91-97 © IAEME 97 4. CONCLUSION A study of the influence of the illuminance and temperature on the electrical output variables of a photovoltaic generator was carried out. A simulation of the photovoltaic generator with and without MPPT control was made. The results obtained show that the electric power supplied by a photovoltaic generator is a function of the temperature of the solar panels and the sunlight received. The electrical power supplied by the photovoltaic generator is optimal for an angle of inclination of the panels of 18.88 °C, which corresponds to the maximum reception level of the solar radiation on the panel. The photovoltaic generator with MPPT control is more stable and faster. REFERENCES  Yves Jannot, 2007, Thermique solaire. Note de cours, Ecole des mines de Nancy.  Ky Thierry S. Maurice, 2007, Système photovoltaïque, dimensionnement pour pompage d’eau, pour une irrigation goute à goute. Mémoire de DEA physique, Université du Burkina Faso.  Alain Ricaud, 2007, Convertisseurs photovoltaïques. Note de cours, Université de Savoie.  Abraham Kanmogne, Guy Edgar Ntamack and Boaz Wadawa, 2011, Energie solaire pour le développement de télécommunication. Livre imprimé aux Editions Universitaires Européennes. ISBN : 978-3-8417-95533, 76 p.  A. F. Oehinger, 1968, Self-adaptive DC converter for solar spacecraft power supply, IEEE Transactions On Aerospace and Electronic Systems, pp. 102-111,  M. Petibon Stephane, 2009, Nouvelles architectures distribuées de gestion et de conversion d’énergie pour les applications photovoltaïques. Thèse de Doctorat, Université de Toulouse.  A. Aziz, 2006, Conceptions des circuits microélectroniques et microsystèmes, Thèse de Doctorat, Université de TOULOUSE III.  C. Hua, C. Shen, 1998, Comparative study of peak power tracking techniques for solar storage system, IEEE Applied Power Electronics Conference, APEC’98, Vol. 2.  G. E. Ahmad, H. M. S. Hussein, and H. H. El-Ghetany, 2003, Theoretical analysis and experimental veriﬁcation of PV modules, renewable energy, vol. 28, N°. 8.  A. Chouder, F.Guijoan , S. Silvestre, 2008,Simulation of fuzzy-based MPP tracker and performance comparison with perturb & observe method, renewable energy, vol. 11, N° 4.  Mohammed Seddik, S. Zouggar, F.Z.Kadda, A. Aziz, M.L.Ahafyani and R.Aboutni, “The Automatic Voltage Control Developed for the Maximum Power Point Tracking of a PV System”, International Journal of Electrical Engineering & Technology (IJEET), Volume 4, Issue 5, 2013, pp. 173 - 183, ISSN Print: 0976-6545, ISSN Online: 0976-6553.  Aishwarya P. Mulmule, Rambabu A. Vatti and Pratik M. Porwal, “MPPT Technique to Improve Efficiency in Wind-Solar Hybrid System”, International Journal of Electrical Engineering & Technology (IJEET), Volume 4, Issue 6, 2013, pp. 74 - 82, ISSN Print: 0976-6545, ISSN Online: 0976-6553.  Anto Joseph, Nagarajan and Antony Mary, “A Multi Converter Based Pure Solar Energy System with High Efficiency MPPT Controller”, International Journal of Electrical Engineering & Technology (IJEET), Volume 4, Issue 4, 2013, pp. 205 - 212, ISSN Print: 0976-6545, ISSN Online: 0976-6553.