The energy utilization efficiency of the photovoltaic can be significantly improved by employing the MPPT (Maximum power point trackers) method. The MPPT is one of the key technologies in photovoltaic generation system;it allows extraction of maximum available power from the photovoltaic (PV) array.The maximum available power is tracked using specialized algorithms such as Perturb and Observe (P&O), and Incremental Conductance (InCd), which are widely applied in the MPPTcontroller due to their simplicity and easy implementation. This paper presents a detailed comparison of their theories and their simulations under the Matlab / Simulink environment. The obtained results show that the use of MPPT control improves in a considerable way the performance of PV systems

Bouhouch, L.

Elyaqouti, M.

Farhat, S.

Hakim, Safa

Moudden, A.

English

The energy utilization efficiency of the photovoltaic can be significantly improved by employing the MPPT (Maximum power point trackers) method. The MPPT is one of the key technologies in photovoltaic generation system;it allows extraction of maximum available power from the photovoltaic (PV) array.The maximum available power is tracked using specialized algorithms such as Perturb and Observe (P&amp;O), and Incremental Conductance (InCd), which are widely applied in the MPPTcontroller due to their simplicity and easy implementation. This paper presents a detailed comparison of their theories and their simulations under the Matlab / Simulink environment. The obtained results show that the use of MPPT control improves in a considerable way the performance of PV systems

Revues Scientifiques Marocaines

7 Comparison of MPPT techniques...S. Hakim, M. Elyaqouti, S. Farhat, L. Bouhouch and A. MouddenFrontiers in Science and Engineering - Vol. 5 - n° 2 - 2015An International Journal Edited by The Hassan II Academy of Science and TechnologyComparison of MPPT techniques:“P&O” and “InCd” for PV systemsS. Hakim1, M. Elyaqouti2, S. Farhat2, L. Bouhouch2 and A. Moudden11 LMTI, Faculty of Sciences of Agadir (FSA),University Ibn Zohr, BP 8106, Agadir, Maroc2 ERTAIER, Superior school of Technology (EST), BP 33/S, Agadir, MarocCorresponding author E-mail: safa.hakim@edu.uiz.ac.maAbstract. The energy utilization efficiency of the photovoltaic can be significantly improved by employing the MPPT (Maximum power point trackers) method. The MPPT is one of the key technologies in photovoltaic generation system;it allows extraction of maximum available power from the photovoltaic (PV) array.The maximum available power is tracked using specialized algorithms such as Perturb and Observe (P&O), and Incremental Conductance (InCd), which are widely applied in the MPPTcontroller due to their simplicity and easy implementation. This paper presents a detailed comparison of their theories and their simulations under the Matlab / Simulink environment. The obtained results show that the use of MPPT control improves in a considerable way the performance of PV systems.Key words: DC-DC power conversion; Matlab/ Simulink; Maximum Power Point Tracking (MPPT); Photovoltaic (PV) power systems.1. IntroductionWith the increasing demand of electrical energy and the rise of the global warming, it is natural that scientific research is increasingly oriented towards renewable energies development [1]. These technologies have an important role in solving the mentioned greatest issues [2].Nowadays it is an indisputable fact that people are obliged to cover their continuously increasing energy needs with new, inexhaustible, and environmentally friendly electric power sources[3]. Among of renewable sources, PV generation is gaining increased importance and has become quite popular thanks to inherent advantages like absence of fuel cost, no noise and wear due to absence of moving parts, little maintenance and not producing any green house gasses[4].So the PV is an attractive source of energy. Abundant and ubiquitous, this source is one of the most important renewable-energy sources that have been increasing worldwide year by year[5].However, a simple system configured with PV generator (PVG) presents production loss because it does not operate at the maximum power point (MPP). To solve this problem it is possible to insert a DC/DC converter between the PVG and the load. This latter, besides the typical functions assigned to the controllers, it can control the seeking of the MPP. This converter is named MPPT system [6].Several MPPT techniques have been proposed in the literature, such as “Perturb and Observe”, “Incremental Conductance”, “Parasitic Capacitance”, “Constant Voltage”, and “Artificial intelligence techniques”. These methods vary in their simplicity, convergence speed, and hardware implementation [7].On the 8 Comparison of MPPT techniques...S. Hakim, M. Elyaqouti, S. Farhat, L. Bouhouch and A. MouddenFrontiers in Science and Engineering - Vol. 5 - n° 2 - 2015An International Journal Edited by The Hassan II Academy of Science and Technologyone hand, conventional methods, as “Perturb and Observe”, guarantee acceptable performances, and are easy to implement. On the other hand, artificial intelligent methods perform better but are generally more complicated to implement; they also require relatively high performance of control processor [5].Our paper is organized as follows: after an introduction, a brief description of photovoltaic and modeling of the system are presented in section 2. Section 3 describes the implementation of the chosen MPPT algorithms; “P&O” and “InCd”. Results and discussions are given in section 4. Finally, we conclude our investigations in section 5.2. System modelingThere are multiple ways of achieving impedance matching for the solar panel to the load: a general diagram is presented in Fig. 1. The system is composed of a MPP computing device and a DC-DC converter.Figure 1: Block diagram of the proposed PVG system.2.1. PV panel modelThe PV panel studied in this paper is Kyocera KC40 [8] that is installed in ERTAIER laboratory (Research team in Advanced Technologies and Engineering of Renewable energies located at University of Technology of Agadir). Table 1 summarizes the used electrical characteristics and parameters for modeling the PV panel:Parameter ValueOpen circuit voltage VocMaximum power voltage VmShort circuit current IscMaximum power current ImMaximum power Pm21.5 V16.9 V2.48 A2.34 A40 WTable 1: PV cell’s parametersA solar cell is a basic building block of a PV system. Normally, a small solar cell generates about one watt. A group of solar cells are connected in series and parallel circuits to generate high power and this combination is called PV panel.The PV cell can be represented by the electrical model shown in Fig. 2. This model consists of a current source, a diode D, and a pair of resistors.9 Comparison of MPPT techniques...S. Hakim, M. Elyaqouti, S. Farhat, L. Bouhouch and A. MouddenFrontiers in Science and Engineering - Vol. 5 - n° 2 - 2015An International Journal Edited by The Hassan II Academy of Science and TechnologyFigure 2: Equivalent circuit diagram of a solar cellThe I-V characteristic of PV cells is expressed by the following equation (1). Sometimes, to simplify the model, the effect of the shunt resistance is not considered, i.e. Rsh is infinite, so the last term in (1) is neglected.I = I ph I s exp(q (V + Rs I )nKT) 1V + Rs IRsh   (1)Where:ParameterI,VIphIsqnKTRs, RshCurrent and Voltage of PV cell (A)PV generated current (A)Diode saturation current (A)Electronic charge (= 1.6 10-19 C)Diode ideality factorBoltzmann’s constant (= 1.38 10-23 J/K)The solar array panel absolute temperature (°K)Serial and Parallel resistorTable 2: Equation’s parameters2.2. Static converter Boost type’sThe converter is used to increase the output voltage, compared to that delivered by the source; its simplest form is shown in scheme of Fig. 3. In the reference [9], the authors present the design method of boost converters. The table 3 summarizes the parameters values used by these authors.Figure 3: Diagram of the Boost converter10 Comparison of MPPT techniques...S. Hakim, M. Elyaqouti, S. Farhat, L. Bouhouch and A. MouddenFrontiers in Science and Engineering - Vol. 5 - n° 2 - 2015An International Journal Edited by The Hassan II Academy of Science and TechnologyBoost ConverterCondenser C 7.5 mFInductor L 50 mHResistor Rc 0 WResistor RL 1 WCondenser of  Coupling Condenser C1 440 nFLoad Resistor Ro 12 WTable 3: Parameters of Boost converter3. MPPT algorithms3.1. “P&O” commandThe most commonly used MPPT algorithm is “P&O” (Perturb and Observe), due to its ease of implementation in its basic form.Thus, if the operating voltage of the PV array is perturbed in a given direction and dP/dV > 0, it is known that the perturbation has moved the PV panel operating point toward the MPP. The P&O algorithm would then continue to perturb the PV array voltage in the same direction. If dP/dV < 0, then the change has moved the operating point of PV panel, away from the MPP, and the P&O algorithm reverses the direction of the perturbation.A problem with P&O is that it oscillates around the MPP in steady state operation. It also can track in the wrong direction, away from the MPP, increasingly rapidly when the irradiance levels increases or decreases. There are several variations of the basic P&O that have been designed to minimize these drawbacks[10].3.2. “InCd” commandThe incremental conductance algorithm seeks to overcome the limitations of the P&O algorithm by varying a PV panel’s incremental conductance to compute the sign of dP/dV without a perturbation.The incremental conductance algorithm is derived by differentiating the PVpanel power with respect to voltage (dP/dV), and setting the result equal to zero (dP/dV = 0).Beginning with this condition, it is possible to show that, at MPP the dI/dV = -I/V. Thus, the MPPT based on incremental conductance achieves the MPP and stop disturbing the operating point. If the condition is not met, the relationship between dI/dV and -I/V can be used to determine the direction in which the voltage must be changed in order to reach the MPP.This relationship is deduced from the fact that dP/dV is negative when the operating point is to right of “MPP” and positive when it’s to the left of “MPP”[10].“InCd” algorithm has advantages over “P&O” in that it can determine when the operating point has reached the “MPP”, whereas “P&O” oscillates around the MPP. Also, “InCd” can track rapidly the increasing, and decreasing irradiance, with higher accuracy than “P&O” without oscillations. One disadvantage of InCd algorithm is his increased complexity when compared to “P&O”. This leads at an increases in computational time, and slows down the sampling frequency of the PV panel voltage and current [10].4. Results and interpretationsFigures 4 and 5 show that the current and the power extracted at a fixed temperature (T = 25 °C), increase proportionally with the solar flux. Indeed the maximum power is very sensitive to the variations of irradiation. 11 Comparison of MPPT techniques...S. Hakim, M. Elyaqouti, S. Farhat, L. Bouhouch and A. MouddenFrontiers in Science and Engineering - Vol. 5 - n° 2 - 2015An International Journal Edited by The Hassan II Academy of Science and Technology2.521.510.50 5 10 151000 W/m2800 W/m2600 W/m2400 W/m220 25Voltage (V)Current (A)Figure 4: Current-voltage characteristics I(V)Power (W)403020105 10 15 20 25 30Voltage (V)Figure 5: Power-voltage characteristics P(V)After several tests, for example for radiation (G = 1000 W/m2), and at ambient temperature (25 °C), the simulations results of the power provided by the PVGshown in Fig. 6 show that the system converges quickly towards maximum power point (MPP) after a less than 240 ms, applying MPPT algorithm using the controller «P&O» and after 450 ms in the case of the controller «InCd».Once the desired «MPP» is reaches, the controller oscillates around the MPP. We noted also that the «P&O» method produces oscillations around the MPP. While the «InCd» technique has the advantage over the «P&O» method that it can reach the MPP without oscillating around this value. So the technique «InCd» is much more stable.But «P&O» has the potential to be very competitive with other methods, if it is properly optimized and leads to an efficiency which is equal to that obtainable by the «InCd» method.353025201510500 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.80.5630.530Time(s)P&OINCInCdP&OPower(W)0.58 0.62Figure 6: Comparison between “P&O” and “InCd” techniques12 Comparison of MPPT techniques...S. Hakim, M. Elyaqouti, S. Farhat, L. Bouhouch and A. MouddenFrontiers in Science and Engineering - Vol. 5 - n° 2 - 2015An International Journal Edited by The Hassan II Academy of Science and TechnologyIn order to validate our results, we compared our simulations with experimental results obtained by my colleagues [11] in our ERTAIER laboratory, using a DAQ acquisition card. Figure 7 summarizes the obtained results.35302520151050 1 2 3 4 5 6 7 86 89 10Power(Watt)Time(s)Experimental Result for G=1000 w/m2 and T=26 °CP&OInCd3130.53029.5Figure 7: Comparison between the experimental results of “P&O” and “InCd” techniques [11]We can deduce that this experience confirms the simulation results that we have obtained. We note that the practical response time is slightly larger to the simulated; this is probably due to the time of acquisition and processing of the acquired data on the card.5. ConclusionIn this work, we have studied and analyzed, by modeling and simulating under Matlab/Simulink, the operation of a PV system. The latter has a load controlled by a Boost converter. The control is provided by two types of MPPT control which are “P&O” and “InCd”.The obtained results based on simulations and experimental validation, show that the use of MPPT control improves in a considerable way the performance of PV systems. A comparison between the two algorithms confirms that there is a significant improvement in stability around the PPM by using the “InCd”. Indeed, we note that the technique “InCd” is much more stable, because we have observed that the “P&O” method produces oscillations around the MPP, whereas the “InCd” technique can reach the MPP without oscillations. However, it happens that the”P&O” method, when properly optimized, can have MPPTefficiencies well in excess of 97%,and is highly competitive against other MPPT algorithms.13 Comparison of MPPT techniques...S. Hakim, M. Elyaqouti, S. Farhat, L. Bouhouch and A. MouddenFrontiers in Science and Engineering - Vol. 5 - n° 2 - 2015An International Journal Edited by The Hassan II Academy of Science and TechnologyReferences[1] Dorin Petreuş, Toma Pătărău, Stefan Dărăban, Cristina Morel, Brian Morley, A novel maximum power point tracker based on analog anddigital control loops, Solar Energy, Vol. 85, Issue 3, (2011), pp. 588-600.[2] S.A.KH. Mozaffari Niapour, S. Danyali, M.B.B. Sharifian, M.R. Feyzi, Brushless DC motor drives supplied by PV power system based on Z-source inverter and FL-IC MPPT controller, Energy Conversion and Management Vol. 52, Issues 8-9, (2011), pp. 3043-3059.[3] Sotirios B. Skretas, Demetrios P. Papadopoulos, Efficient design and simulation of an expandable hybrid (wind–photovoltaic) power system with MPPT and inverter input voltage regulation features in compliance with electric grid requirements, Electric Power Systems Research, Vol. 79, Issue 9, (2009), pp. 1271-1285.[4] S.M. Ali, Punyashree Pattanayak, Prasun Sanki, R.R. Sabat, Modeling and control of grid-connected hybrid photovoltaic distributed generation system,IJESET, ISSN: 2231–6604, Vol. 4, Issue 1, (2012), pp. 125-132.[5] A.Mellit, H. Rezzouk, A. Messai, B. Medjahed, FPGA-based real time implementation of MPPT-controller for photovoltaicsystems, Renewable Energy,Vol. 36, Issue 5, (2011), pp. 1652-1661.[6] V. Salas, E. Olıas, A. Lázaro, A. Barrado, Evaluation of a new maximum power point tracker (MPPT) applied to the photovoltaic stand-alone systems, International Conference on Physics, Chemistry and Engineering, Solar Energy Materials and Solar Cells,Vol. 87, Issues 1-4, (2005), pp. 807-815.[7] Nacerk M’Sirdi, Abdelhamid Rabhi, Mouna Abarkan, A new VSAS approach for maximum power tracking for renewable energy sources (RES), Energy procedia 42, (2013), pp. 708-717.[8] KYOCERA Corporation, KC40, High Efficiency Multicrystal Photovoltaic Module, http://www.kyocerasolar.com/assets/001/5158.pdf[9] M. Meddah, M. Bourahla, N. Bouchetata, Synthèse des convertisseurs statiques DC/AC pour les systèmes photovoltaïques,Revue des Energies Renouvelables, ICESD’11, Adrar, (2011), pp. 101112.[10] D.P. Hohm, M.E. Ropp, Comparative Study of Maximum Power Point Tracking algorithms,Progress in Photovoltaics: Research and Applications,Vol. 11, Issue 1, (2003), pp. 47-62.[11] S. Farhat, R. El Moutawakil Alaoui, L. Bouhouch, A. Ihlal, P&O and InC Implementation, accepted in IREE journal, (March 2015).

Comparison of MPPT techniques: “P&O” and “InCd” for PV systems

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Comparison of MPPT techniques: “P&O” and “InCd” for PV systems

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