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40220130405018 2

  1. 1. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING & ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME TECHNOLOGY (IJEET) ISSN 0976 – 6545(Print) ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), pp. 173-183 © IAEME: www.iaeme.com/ijeet.asp Journal Impact Factor (2013): 5.5028 (Calculated by GISI) www.jifactor.com IJEET ©IAEME THE AUTOMATIC VOLTAGE CONTROL DEVELOPED FOR THE MAXIMUM POWER POINT TRACKING OF A PV SYSTEM Mohammed SEDDIK1, S. Zouggar1, F.Z.Kadda1, 1 A. Aziz1, M.L.Ahafyani1, R.Aboutni1 Higher Institute of Technology EEML-BP. 473 Hay El Qods-60000 - Oujda, Morocco ABSTRACT The output power of the Photovoltaic generator is influenced by the climate changes, Such as the temperature and the illumination. So, a maximum power point tracking is required to optimize the performance of the PV system. Several MPPT techniques have been proposed in the literature, among them we find the voltage control technology (the optimal output voltage of the PV generator is weakly depending on the illumination), which has a major drawback; it neglects the effect of the temperature on the PV generator. In this article, we present the Automatic Voltage Control developed (AVCD) that takes into account the changes in the temperature. The PV model integrating the AVCD and the Power Interface DC-DC Boost are implanted in the environment ORCAD / PSPIC. The simulation and experimental results obtained are in very good agreement and show excellent performance. Keywords: Hybrid System, Photovoltaic System, Automatic voltage control, Boost Converter. 1. INTRODUCTION This work is a part of the energy management and the optimization of a hybrid system (HS), that combines a photovoltaic generation system (PV) and wind turbine which are coupled via a DC bus associated with a battery bank (figure1) [1]-[12]. With the HS, we can ensure the permanent energy required by the load, by overseeing the power produced by the hybrid system (PV & Wind Energy) and the level of charge and discharge of the battery. Generally, the optimization of a hybrid system involves the optimization of the PV system and the wind turbine. So the final goal is to provide a control laws to optimize the elements constituting the hybrid system. 173
  2. 2. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME Fig.1. Photovoltaic & Wind Hybrid System In this work, we are particularly interested in the photovoltaic system to operate it under the optimal conditions. The PV power has non-linear characteristics; these characteristics have a Maximum Power Point (MPP) depending on the illumination and the temperature. So, it is imperative to track the maximum power of the PV. This tracking is usually done using adapters that are interposed between the generator and the receiver. This adapter is a static converter controlled using laws which are known by the name MPPT. Several MPPT techniques of PV systems have been proposed as the perturbation and observation (P & O) [1, 2, 3], the incremental conductance (IncCond) [4,5], the method of short circuit current (Isc ) [6], the method of open circuit voltage (Voc) [7], and the subservience control voltage technique of PV generator [8], It maintains the terminal voltage of the PV generator at its maximum value because the optimum voltage depends very little of the illumination, therefore the output power is then maintained to the optimum one. This command was attractive because of its simplicity of implementation and its lower cost. But, it has a major drawback; it neglects the effect of the temperature on the PV generator, knowing that the temperature is an important parameter in the behavior of the photovoltaic panel. Indeed, if the temperature increases, the maximum power decreases, the MPPT point moves to the left and the open circuit voltage (Voc) decreases, as shown in figure 2. Fig.2. Evolution of the characteristic P (V) of the PV according to the temperature In this article, we present theAutomatic Voltage Control developed (SCV,) which takes into account the temperature changes. To do this, we have added a digital potentiometer to the SCV, which tracks the maximum power point even if the temperature varies. The simulation results (ORCAD / PSPICE) obtained show that CDAT has good results and that the controller is effective and robust. 174
  3. 3. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME 2. THE CHARACTERISTICS OF THE SOLAR PANEL The Mitsubishi UD180MF5 commercial PV module installed in our laboratory LGEM was selected in this study [9, 12]. The characteristics of the PV module given by the manufacturer to the temperature 25 C shown in Table 1 plus the model of the solar cell were used in the simulations to obtain the output characteristics of the solar panel [10, 11]. Parameter Value Number of cells 50in series Maximum power rating 80Wp Open circuit voltage (Voc) 30.4V Short circuit current (Isc) 8.03A Maximum power voltage (Vmp) 24.2V Maximum power current (Imp) 7.45A TABLE 1: Electrical Characteristics of the mitsubishi UD180MF5 PV module [9] The electrical characteristics of the PV module are represented generally by the current in function of the voltage (I-V) and the power according to the voltage (P-V). The curves of Figures 3 and 4 show the characteristics of the PV module for different intensities of solar illumination. It should be noted that each curve has a maximum power point which is the optimal point for the effective use of the panel. This depends on the values of the temperature and the illumination. 10A 200W 8A 150W 6A 100W 4A 50W 2A 0A 0W 0V 10V 20V W(V1) V_V1 0V 30V 10V 20V I(V1) V_V1 30V a) Characteristic P-V b) Characteristic I-V Fig.3. Characteristics of the PV module referenced by UD180MF5 In Figure 4 we represent the influence of the temperature on the characteristic of the PV for an illumination of 1000W/ m² and deferent temperature values (60 °C, 25 °C, 0 °C). 175
  4. 4. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME Fig.4. Characteristics P-V of the PV module referenced by UD180MF5 3. DESCRIPTION OF THE PROPOSED SYSTEM The Figure 5 shows the block diagram of a photovoltaic chain that feeds a resistive load (Rs).which is formed by the following elements: a photovoltaic generator (PVG), a quadripole adaptation which is an energy converter of type booster (boost) and a tracking device (the Automatic Voltage Control developed (MPPT)) [8]. Boost converter has the role of raising the voltage at the output and regulating the voltage at the terminals of the PVG at a fixed value, by adjusting the duty ratio. The most important function of the MPPT which represents the main objective of the present work is to adjust the output voltage of the panel at a constant value (24.2V), so that the panel provides the maximum power to the load. Fig.5. Chain of a photovoltaic conversion system with CS controlled by a control voltage 4. DC-DC CONVERTER (BOOST) The basic circuit topology of the Boost DC-DC is shown in Figure 6. Fig.6. Boost Circuit 176
  5. 5. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME The specifications is set for a voltage across the load less than 100 V and with a residual ripple in the output voltage does not exceed 10 mV and the input does not exceed 100 mV. The chopping frequency is set at 20 KHz. The duty cycle (eq 1) is defined as the ratio between the duration of the high period of the signal (ton) and its period T= ton+toff. D= t on t = on t on + t off T (1) Equation 2 of the duty ratio gives the control law which is produced by the MPPT system to operate the PV at its maximum power point for a given load, illumination and temperature. ܸ‫ ݏ‬ൌ 5. ܸ‫ݒ݌‬ 1െߙ ሺ2ሻ THE PROPOSED MPPT CONTROL The diagram of the figures 7 and 8 shows the topology of the Automatic Voltage Control developed. The latter generally includes: a temperature sensor, a digital potentiometer which varies the picked voltage value of the PV, a differential amplifier which calculates the error between the voltage taken from the PV and the reference voltage, an inverting operational amplifier 10 for amplifying the error, a PI corrector, an integrator RC, and a comparator which compares the voltage to a triangular wave signal to generate a pulse width modulated signal (PWM) (figure 8). To measure the temperature, we used the open circuit voltage which gives a picture of the temperature. The digital potentiometer used contained generally the integrated circuit CD4051 which is an analog switch of type 1 position among eight (figure 7). In our case, we have used a bridge resistor divider at several points, consisting of nine resistors placed in series. Then, the temperature of the analog switch is used for connecting to an intermediate point of the resistor network. Finally, we have the equivalent of a potentiometer. The resistance values are fixed to vary the value of the terminal voltage of the PV from 19.1V to 26.2 by one steps (1V). PV CD4051B 1 5 2 4 11 10 9 6 0 I/O2 I/O3 I/O4 I/O5 I/O6 A B C INH Temperature Sensor Fig.7. Digital Potentiometer 177 O/I I/O7 V EE 12 I/O1 V DD 15 I/O0 7 14 16 13 3 AVC
  6. 6. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME Fig.8. Synoptic Diagram of the AVC 6. SIMULATION RESULTS 6.1. Without Digital Potentiometer A first simulation of the PV system was conducted by varying the temperature from 25 ° C to 60 ° C. the figure 9 illustrates the variation of the output power and The terminal voltage of the PV. Indeed, up to t = 1.5s, the temperature is 25 ° C, the input voltage fluctuates around 24V (fig.9.b) and the power supplied by the PV oscillates around its optimal value (180W) (fig.9.a). At time t = 1.5s, the temperature change (60 ° C-Voc = 27.1), the input voltage of the chopper still oscillates about 24V and the power delivered by the PV fluctuates around 130W (fig 9.a). Knowing that the optimum power that corresponds to the temperature 60°C is 150W and the optimum voltage is 21.1V as shown in the figure 4, it is noted that there is a loss of power of 20W. 250W 42V 36V 195W 30V 24V 130W 18V 12V 65W 6V 0W 0V 0s 0.5s 1.0s 0s I(L2)*V(V_PV) 0.5s 1.0s V(V_PV) Time Time a) Power b) voltage Fig.9. : Power supplied by the PV and the terminal voltage of the PV with a temperature variation of (25 ° C-60 ° C) for the illumination of 1KW / m² 6.2. With digital potentiometer The second simulation was performed for a MPPT controller containing the digital potentiometer and for a temperature range from 25 °C to 60 °C and then at 0 °C. The figure 10 shows the power produced by the PV and the terminal voltage of the PV. As we can see, up to time t = 1.5s, the temperature is 25 °C, the voltage across the PV oscillates around 24V (fig 10.b) and the power 178
  7. 7. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME supplied by the PV reaches its optimum value (180W) (fig 10 a). As at time t = 1.52s the temperature is set to 60 °C, and we note that the input voltage of the chopper fluctuates around 21.3V (fig 10.b) and the provided power from the PV is 150W (fig 10.a). At time t = 1.5s, the temperature reaches 0 °C, we observe that the output voltage of the PV oscillates around 27.2V (fig 10.b) and the power supplied by the PV is 200W (fig 10.a). Consequently, the command tracks the maximum power point even if the temperature varies. 250W 35V 30V 200W 25V 150W 20V 100W 15V 10V 50W 5V 0W 0V 0s Fig.10. 7. 0.5s 1.0s V(V_PV)*I(I_pv) Time 1.5s 0s 0.5s 1.0s 1.5s V(V_PV) Time a)Power b)Voltage The power delivered by the PV and the terminal voltage of the PV with a temperature change (25 °C / 60 °C / 0 °C) EXPERIMENTAL RESULTS In order to validate the simulation results we have realized the system of figure 5.the Figures 11 and 12 show the PV panels (UD180MF5) used and the tester bank. The different blocks of photovoltaic (converter, AVCD control) were performed on test models as recorded in Figure 13. Fig.11. PV installed in our laboratory [9] 179
  8. 8. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME Fig.12. Photovoltaic system used for experimentation Fig.13. Boost converter with the CATD We set the parameters of the MPPT control for regulating the voltage of the PVG to the desired optimum value which varies from 19.1V to 26.3V. In this sites the optimal voltage of the PV range from 19.1V (Voc = 25.1) to 24.1V (Voc = 30.1V) which corresponds to a variation of the open circuit voltage (Voc) of 25.1V to 30.1 V. The different measurements are performed during a day where the open circuit voltage is 27.4V (fig 14.c). This value corresponds to the optimal voltage 21.1V (fig 4). On figures 14, 15, 16, we reproduce the voltage and the current measurements at the output and the input of the boost converter, as well as the signals controlling the switch of the converter for a load of 20 . We can see that the AVCD command instantaneously converges the photovoltaic system to the optimal conditions and all the electrical values oscillate around the optimal values. We can see that the AVCD command instantaneously photovoltaic system converges to the optimal conditions and that all electrical values oscillate around the optimal values. The input voltage (output) of the converter oscillates around 21.13V (fig 14.a) and the output is 44.9V (fig 14.b), and the duty cycle value oscillates around the value 0.5236 (fig16). 180
  9. 9. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME a)The voltage across the terminals of thePV b)The output voltage of the converter c) The open circuit voltage of the PV Fig.14. The input (Vin) and the output voltage (Vout) of the converter and The open circuit voltage of the PV a)input b) output Fig.15. The Current at the input and at the output of the converter 181
  10. 10. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME Fig.16. Signal controlling the BOOST switch From these results we can deduce the power delivered by the PV (Pe) and the power consumed by the load (Ps). The calculated results are: Pe= 123.39W Ps=104.617W On this test, the yield measured according to Equation 3 is 84.78% with a power supplied by the PVG of 123.39W. ηൌ 8. Ps Pe CONCLUSION In this paper, we validated in simulation and experimentally that the automatic voltage control developed (AVCD) can follow the maximum power point of the PV generator even if the temperature varies. It regulates the power delivered by the PV generator at its optimum value. The different experimental results presented show a very good agreement with those simulated in Orcad-Pspice. These results demonstrate the robustness and reliability of the proposed system. REFERENCE [1]. Zhong Zhi-dan, Huo Hai-bo, Zhu Xin-jian,Cao Guang-yi, Ren Yuan, 2008. “Adaptive maximum power point tracking control of fuel cell power plants”, J. Power Sources, Vol. 176, pp. 259–269. [2]. O. Wasynczuck, 1983. “Dynamic Behavior of a Class of Photovoltaic Power Systems”, IEEE Trans. Apparatus and Systems, Vol. PAS-102, No. 9, pp. 3031-3037. [3]. C. hua, J.Lin, and C.Shen. “Implementation of a DSP-Controlled Photovoltaic System with Peak Power Tracking” IEEE transactions on industrial electronics, vol. 45, no. 1, February 1998. [4]. C. R. Sullivan and M. J. Powers, “A high-efficiency maximum power point tracker for photovoltaic array in a solar-powered race vehicle,” in Proc. IEEE PESC, 1993, pp. 574–580. 182
  11. 11. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME [5]. K. H. Hussein et al., “Maximum photovoltaic power tracking: An algorithm for rapidly changing atmospheric conditions,” Proc. Inst. Elect. Eng. vol. 142, pt. G, no. 1, pp. 59–64, Jan. 1995. [6]. T.Noguchi, S.Togashi, R.Nakamoto, 2002. “Short-Current Pulse-Based Maximum-Power Point Tracking Method for Multiple Photovoltaic and Converter Module System”, IEEE Trans. On Industrial Electronics, Vol. 49, pp. 217-223. [7]. J. H. R. Enslin, M.S.Wolf, D.B.Snyman and W.Swiegers, 1997. “Integrated Photovoltaic Maximum Power Point Tracking Converter”, IEEE Trans. on Industrial Electronics, Vol. 44, pp. 769-773. [8]. M. Seddik , S. Zouggar, T. Ouchbel, M. Oukili, A. Rabhi, A. AZIZ, M.L. Elhafyani “A stand-alone system energy hybrid combining wind and photovoltaic with voltage control« feedback loop voltage”. International Journal of Electrical Engineering IJEET, vol. 6, n°2, 2010, pp 9-13. [9]. http://www.mitsubishielectricsolar.com/images/uploads/documents/specs/UD5_spec_sheet_1 75W_190W.pdf. [10]. A.AZIZ. “Propriétés électriques des composants électroniques minéraux et organiques”. “Conception et modélisation d'une chaîne photovoltaïque pour une meilleure exploitation de l'énergie solaire” Rapport LAAS N°06234 Doctorat, Université Paul Sabatier, Toulouse, 173 pages ,28 Novembre 2006 ; [11]. T. Yu, T. Chien, “Analysis and simulation of characteristics and maximum power point tracking for photovoltaic systems”. in: International Conference on Power Electronics and Drive Systems, 2009, pp. 1339-1344. [12]. M. Seddik, S. Zouggar, M. Oukili, T. Ouchbel, A. Aziz, M.L.Elhafyani, F.Z.Kadda, “The Digital Energy Management of a Stand- Alone Hybrid System Photovoltaic-Wind” International Journal of Engineering and Innovative Technology (IJEIT) vol. 3, issue 3, 2013, pp 156-163. [13]. M.Sujith, R.Mohan and P.Sundravadivel, “Simulation Analysis of 100kw Integrated Segmented Energy Storage for Grid Connected PV System”, International Journal of Electrical Engineering & Technology (IJEET), Volume 3, Issue 2, 2012, pp. 164 - 173, ISSN Print: 0976-6545, ISSN Online: 0976-6553. [14]. T.Balamurugan, Dr.S.Manoharan, P.Sheeba and M.Savithri, “Design a Photovolatic Array with Boost Converter using Fuzzy Logic Controller”, International Journal of Electrical Engineering & Technology (IJEET), Volume 3, Issue 2, 2012, pp. 444 - 456, ISSN Print: 0976-6545, ISSN Online: 0976-6553. [15]. Manoj Kumar, Dr. F. Ansari and Dr. A. K. Jha, “Analysis and Design of Grid Connected Photovoltaic System”, International Journal of Electrical Engineering & Technology (IJEET), Volume 3, Issue 2, 2012, pp. 69 - 75, ISSN Print : 0976-6545, ISSN Online: 0976-6553. [16]. M D Goudar, B. P. Patil and V. Kumar, “A Review of Improved Maximum Peak Power Tracking Algorithms for Photovoltaic Systems”, International Journal of Electrical Engineering & Technology (IJEET), Volume 1, Issue 1, 2010, pp. 85 - 107, ISSN Print: 0976-6545, ISSN Online: 0976-6553. 183

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