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Maximum Power Point Tracking using modified Perturb & Observe and Incremental Conductance Techniques Bilal Masoodi, M. Shahzad Siddiqueii, M. Zia-ul-Haqiii Department of Electrical Engineering, Superior University, 15-KM Raiwind Road Lahore Email: [email protected], [email protected], [email protected] Abstract: The development of renewable energy has been an increasingly critical topic in the 21st century with the growing problem of global warming and other environmental issues. With greater research, alternative renewable sources such as wind, water, geothermal and solar energy have become increasingly important for electric power generation. Although photovoltaic cells are nothing new, their use has become more common, practical, and useful for people worldwide. Although each cell output is relatively low voltage, if many are connected in series, a solar photovoltaic (PV) module is formed. Although the price for such cells is decreasing, making use of a solar cell module still requires substantial financial investment. At a given temperature and insolation level, PV cells supply maximum power at one particular operation point called the maximum power point tracking (MPPT). However, the MPP locus varies over a wide range, depending on PV array temperature and insolation intensity. Instantaneous shading conditions and aging of PV cells also affect the MPP locus. In this research paper two reformed algorithms have been proposed for MPPT, the most widely used ones are the ‘Perturb and Observe’ (P&O) and the Incremental Conductance algorithms. The duty cycle of the converter will be controlled, so that the source will send maximum power to the load. The research paper presents a new reformed technique of harvesting MPP from PV cells after evaluating the previous ones. All the previous techniques were thoroughly studied before making any reform in the traditional MPP techniques. Both techniques have their own significance at different situations of weather. In this paper new technique is introduced by using both of above P&O and Incremental Conductance. Keywords – Perturb and Observe (P&O), Maximum Power Point Tracking (MPPT), Photo Voltaic Cell (PV cell) I. Introduction: History of PV Cells The history of PV dates back to 1839 when a French physicist, Edmund Becquerel, discovered the first photovoltaic effect when he illuminated a metal electrode in an electrolytic solution. Thirty-seven years later British physicist, William Adams, with his student, Richard Day, discovered a photovoltaic material, selenium, and made solid cells with 1~2% efficiency which were soon widely adopted in the exposure meters of camera. In 1954 the first generation of semiconductor silicon-based PV cells was born, with efficiency of 6%, and adopted in space applications. Today, the production of PV cells is following an exponential growth curve since technological advancement of late ‘80s that has started to rapidly improve efficiency and reduce cost. Topology about PV Cells Renewable energy technologies are playing an increasingly important role in supplying the world’s electricity demands. In particular, the PV generation system, a promising source of energy for the future, is evolving rapidly and showing an industrial growth of approximately 40% per year worldwide. Solar energy which is free and abundant in most parts of the world has proven to be an economical source of energy in many applications. The most important aspect of a solar cell is that it generates electrical energy directly from sun light through the photovoltaic module, made up of commonly silicon cells. The energy, the earth receives from the sun is so enormous and so lasting that the total energy consumed annually by the entire world is supplied in as short period as half an hour. On a clear day, the sun's radiations on the earth can be 3000 watts per square meter depending on the location. The sun is a clean and renewable energy source, which produces neither green-house effect gas nor noxious waste through its utilization. The photovoltaic process is completely solid state and self-contained. There are no moving parts and no materials are consumed or emitted. Consider the advantages that photovoltaic systems have over competing power options: They are non-polluting with no detectable emissions or odors. They can be stand-alone systems that reliably operate unattended for long periods. They require no connection to an existing power source or fuel supply. They may be combined with other power sources to increase system reliability. They can withstand severe weather conditions including snow and ice. They consume no fossil fuels - their fuel is abundant and free. They can be installed and upgraded as modular building blocks - as power demand increases; more photovoltaic modules may be added Role of MPPT in Solar Energy The PV systems when connected directly to the load result in overall poor efficiency where as such MPPT should have been introduced in PV systems that increase the efficiency of the system. Solar radiations, load impedance and module temperature are the three factors which affect the maximum power extraction from solar PV module. Unlike conventional energy sources, it is desirable to operate PV systems at its MPP. [1] Thus, to make a PV module useful, it is necessary to extract as much energy as possible from such a system. To achieve operation at the MPP, a time varying matching network is required that interfaces the varying source and possibly the varying load [9]. The role of this matching network, called the MPPT network, is to ensure operation of the PV array at its MPP, regardless of atmospheric conditions and load variations. I-V curve of PV module is a function of insolation and temperature which affects output current and voltage [10]. The increased temperature decreases the open circuit voltage (Voc) while increased intensity of solar radiations increases short circuit current (Isc). The concept of MPPT is to monitor the terminal voltage and current continuously and update the control signal accordingly to achieve maximum power point (MPP) [2]. A DC/DC convertor with MPPT algorithm is used between PV module and load to extract maximum available power [11]. An example of MPPT with a typical cell of voltage and current is shown in figure below. It shows where the maximum power point lies for that typical cell is. Figure 1. Typical forward bias I-V characteristics of a PV cell II. Techniques: A Short Review on Conventional MPPT Techniques The conventional P&O algorithm is easy to implement and is most commonly used in battery charging with commercial PV modules. In this method, the operating voltage or current of the PV module, is perturbed and then the power obtained is observed to decide the direction of further changes in the voltage or current [8]. If the power is increased by the perturbation then voltage or current is kept on changing in the same direction until the power begins to fall. The algorithm measures the instant voltage (Vt) and current (It) to calculate the power (Pt) and then compares it with last calculated power (Pt-1) [7]. The algorithm continuously perturbs the system if the operating point variation is positive, otherwise the direction of perturbation is changed. Here is the flow chart for the conventional P&O algorithm Figure 2. Flow Chart of P&O Algorithm The second one is the conventional Incremental Conductance (INC) method. The incremental conductance algorithm of MPPT was developed by K. H. Hussein, I. Muta, T. Hoshino and M. Osakada, however the concept technique was developed by O. Wasyneczuk. They used derivative of conductance to determine the maximum power point (MPP) [12]. The MPP is determined by comparing instant conductance I/V to the incremental conductance ΔI/ΔV and the INC technique is based on the fact that slope of P-V curve is zero at MPP as shown in Fig. 3. [3] This algorithm performs better than P&O algorithm in rapidly varying environment and is robust to the rapidly varying solar radiation. The MPPT speed and accuracy was improved by introducing automatically adjustable variable step size to conventional INC technique [4]. When MPP is far from operating point, the step size is large for fast tracking while during operating point closer to MPP, the step size becomes small to reduce steady state oscillation. accurate and effective than most commonly used P&O algorithms at low solar radiations. Therefore these algorithms are combined with P&O and INC algorithms to increase their effectiveness. The P&O based algorithms oscillate around the MPP in slow varying atmospheric conditions. Therefore to decrease losses due to oscillations, the P&O based algorithms are suitable in only rapidly changing atmospheric conditions and the constant voltage method is fast and sufficient for constant conditions. The two mode control algorithm combines these two algorithms by using incremental conductance method for more than 30% normalized solar radiations and constant voltage method for less than 30% normalized radiations. The flow chart of the algorithm of this method is shown in Fig 4. Figure 3. Flow chart of Incremental Conductance Algorithm The algorithm is modified and the derivative of resistance (dV/dI) is used in place of derivative of conductance. The modified algorithm is variable step-size incremental resistance (INR) algorithm is based on the fact that slope of P-I curve is zero at MPP, positive on the left of MPP, and negative on the right of MPP [13]. Figure 4. Flow Chart of Modified hybrid techniques using two mode control method algorithm III. Modified P&O with INC Algorithm The Modified P&O with INC Algorithm consists of hybrid algorithm using a different algorithm technique along with the P&O method for faster and accurate tracking of MPP [5]. The voltage and current controlled algorithms are more IV. Conclusion In the above research we reviewed previous MPP techniques and also their algorithms. Both of the above techniques have their own significance for faster and slow changing weather conditions. We proposed a new techniques say hybrid both of P&O and INC which actually works in both slow and faster changing conditions of weather. This is basically an advancement in conventional P&O and INC method. From this research we also came to know that both techniques are really efficient for MPPT. [12]. A. Yafaoui., B. Wu and R. Cheung, Implementation of Maximum Power Point Tracking Algorithm For Residential Photovoltaic Systems, 2nd Canadian Solar [1]. Joe-Air Jiang, Tsong-Liang Huang, Ying-Tung Hsiao, Buildings Conference Calgary, June 10 – 14, 2007 Chia- Hong Chen, Maximum Power Tracking for Photovoltaic Power Systems, Tamkang Journal of Science [13]. Dezso Sera, Tamas Kerekes, Remus Teodorescu and and Engineering, 2005, Vol. 8, No. 2, pp. 147-153. Frede Blaabjerg, Improved MPPT algorithms for rapidly changing environmental conditions [2]. Mahmoud A. YOUNIS , Tamer KHATIB, Mushtaq NAJEEB, A Mohd ARIFFIN, An Improved Maximum Power Point Tracking Controller for PV Systems Using [14]. Mohammed A. Elgendy, Bashar Zahawi, Senior Member, IEEE, and David J. Atkinson, Assessment of Artificial Neural Network Perturb and Observe MPPT Algorithm Implementation Techniques for PV Pumping Applications, IEEE [3]. L. MacIsaac, A. Knox, Improved Maximum Power Point TRANSACTIONS ON SUSTAINABLE ENERGY, Tracking Algorithm for Photovoltaic Systems VOL. 3, NO. 1, JANUARY 2012 V. References: [4]. Fu Qiang, Tong Nan, A Strategy Research on MPPT [15]. Ioan Viorel BANU, Răzvan BENIUGĂ, Marcel Technique in Photovoltaic Power Generation System, ISTRATE, Comparative Analysis of the Perturb-andTELKOMNIKA, Vol. 11, No. 12, December 2013, pp. Observe and Incremental Conductance MPPT Methods, 7627~7633 e-ISSN: 2087-278X THE 8th INTERNATIONAL SYMPOSIUM ON ADVANCED TOPICS IN ELECTRICAL [5]. Thomas Bennett, Ali Zilouchian and Roger ENGINEERING May 23-25, 2013 Bucharest, Romania Messenger, Perturb and Observe versus Incremental Conductance MPPT Algorithms [6]. J. Surya Kumari Dr. Ch. Sai Babu, A. 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Shahzad Siddique, Final Year Student and active Researcher at Department of Electrical Engineering, Superior University Lahore [10]. Samer Alsadi, Basim Alsayid, Maximum Power Point Tracking Simulation for Photovoltaic Systems Using Perturb and Observe Algorithm, International Journal of Engineering and Innovative Technology (IJEIT) Volume 2, Issue 6, December 2012, ISSN: 2277-3754 [11]. Ch. Kalpana, Ch. Sai Babu, J. Surya Kumari, Design and Implementation of different MPPT Algorithms for PV System, International Journal of Science, Engineering and Technology Research (IJSETR) Volume 2, Issue 10, October 2013, ISSN: 2278 – 7798 iii M. Zia-ul-Haq, Final Year Student and active Researcher at Department of Electrical Engineering, Superior University Lahore