USE OF BY-PASS DIODE IN MAXIMUM POWER POINT TRACKING SYSTEM

Transcription

1 International Journal of Electrical Engineering & Technology (IJEET) Volume 6, Issue 9, Nov-Dec, 2015, pp.01-06, Article ID: IJEET_06_09_001 Available online at ISSN Print: and ISSN Online: IAEME Publication USE OF BY-PASS DIODE IN MAXIMUM POWER POINT TRACKING SYSTEM S. D. Pagare and Asso Prof A. K. Jhala RKDF COE Bhopal ABSTRACT The shading due to clouds, buildings, tree s etc. may affect the performance of photovoltaic array. Including this variation in temperature, solar separation is some more factors which affect the performance. The complete or partial shadowing of PV array tremendously affects its performance. In case of large PV array systems installed for distributed power generation schemes, the situation may get more complex under partially shaded condition. The multiple peaks generated due to shadowing affect may make PV characteristics more complex. It is significant to understand the maximum peak possibilities in order to extract the maximum possible power. This paper is a attempt to describe the MATLAB-based modeling and simulation scheme suitable for studying the I V and P V characteristics of a PV array under a non-uniform isolation due to partial shading. The present paper will explain a comparative study and give glimpse on different method for maximum power point tracking system. Key words: Power point and Tracking System Cite this Article: Pagare, S. D. and Jhala, A. K. Use of By-Pass Diode in Maximum Power Point Tracking System. International Journal of Electrical Engineering & Technology, 6(9), 2015, pp INTRODUCTION The rapid growing demand of energy is a biggest challenge in present. To accomplish the day by day increasing demand of energy, the energy through sun (solar energy) could be the best solution. Photovoltaic technology is been used for converting solar energy into electrical energy. The use of PV array systems in several electric power applications has been grown in recent past. Even with of the high initial cost and low efficiency, PV system has small operation and maintenance costs as it is a stationary source of energy fabricated from semiconductor material[1]. Because solar energy is having zero pollution and No-negative effect on environment, govt. is also promoting the same and offering subside on establishing solar plants. 1 editor@iaeme.com

2 S. D. Pagare and A. K. Jhala The reduction of output power in solar photo voltaic (SPV) modules can be attributed to many reasons, but the most significant are maximum power point (MPP) mismatch and shadows. Numbers of factors are present which affect the SPV generators performance which cannot be neglect some of them are shadowing effects due to tree leaves, dust or opposite house antennae in urban street. In a large SPV system occupying a wide area of land, moving clouds can also lead to shading. In building integrated SPV systems, SPV modules may be installed with different orientations to fit the building outer wall, which makes the modules receive different levels of brightness of solar light, a circumstances similar to partial shading. The major power reduction due to shading effect can be addressed by judiciously reconfiguring the array and effectively tracking the MPP. The maximum power point tracking (MPPT) technique has been developed such that it can adjust operating point according to the given condition, when no shading effect is present. In the situation of partial shading, problem of multiple peaks is observed in the P-V characteristics. The cause of these multiple peaks is mismatch in individual SPV module characteristics. Modern inverters for solar power plants (SPP) are capable to perform maximum power point tracking. Total efficiency of solar power plant is highly dependent on MPPT performance, which determines the maximum amount of produced electrical energy. In solar power plants without maximum power point tracking energy losses can be up to 30 % higher than in the solar power plants with maximum power point tracking [2]. 2. MAXIMUM POWER POINT TRACKING SYSTEM Because of the lesser efficiency of photovoltaic array most of the energy, impacting over array gets wasted. The algorithm known as maximum power point tracking may be helpful to enhance the performance of solar panel. The MPPT algorithm works on principal of Thevenin, according which the power output of a circuit is maximum when impedance of circuit matches with the load of impedance. So now we have to match the impedance instead of tracking maximum power point. There are different techniques used to track the maximum power point. Few of the most popular techniques are: 1. Perturb and observe (hill climbing method) 2. Incremental Conductance method 3. Fractional short circuit current 4. Fractional open circuit voltage 5. Neural networks 6. Fuzzy logic 3. PERTURB AND OBSERVE The P&O algorithm and hill-climbing, both names refer to the same algorithm depending on how it is implemented. The basic difference between these two is that Hill-climbing involves a deviation of the duty cycle of the power converter and in P&O anxiety on the operating voltage of the DC link between the PV array and the power converter takes place [3]. The deviation of duty cycle of the power converter is the modification of the voltage of DC link between the PV array and the power converter refer as Hill-climbing, so both names refer to the same technique. What 2 editor@iaeme.com

3 Use of By-Pass Diode in Maximum Power Point Tracking System should be the next perturbation is decided by considering the sign of the last perturbation and the sign of the last increment in the power. The perturbation will remain in the same direction if power is incremented, and if power is decreased then next perturbation will be in the opposite direction. The process will be repeated until the point of maximum power will be reached. Then the operating point oscillates around the MPP. 4. INCREMENTAL CONDUCTANCE The slope of the curve between power and voltage of PV module is the deciding factor in incremental conductance algorithm, if it is zero it shows point of MPP positive (negative) on the left of it and negative (positive) on the right. V/ P = 0 at the MPP V/ P > 0 on the left V/ P < 0 on the right The change of MPP voltage is identified by comparing the change of the power to increment of the voltage of current curve. 5. FRACTIONAL SHORT CIRCUIT CURRENT Fractional short circuit current method states that the ratio between array voltage at maximum power V MPP to its open circuit voltage V OC is nearly constant. V MPP k 1 V OC The constant K 1 is having value between 0.71 to Now the value of V MPP can be calculate by periodically measuring V OC. This method is simple and cheap to implement but its efficiency is relatively low due to the utilization of inaccurate values of the constant k1 in the computation of V MMP. 6. PHOTOVOLTAIC CELL To convert the light energy supplied by sun the semiconductor solution is the photovoltaic cell it converts light energy to electrical energy by photovoltaic effect. The energy photons are available with light, if there energy is greater than the energy gap of atomic electronics, than the outer most electrons of atoms are get emitted because of the impact of these photon. These electrons get flow freely and cause current. The construction of photovoltaic cell is similar as the construction of p-n junction diode. A photovoltaic cell is composed of two different layers of silicon one is P-type layer where negative ions are there with one less valence electron and other is N-type layer with positive ions with one extra valence electron. At the junction of these two layers extra electrons of N-layers get diffused with less electron space of P layer and leave region with positive and negative ions only. This space is known as diffusion layer, the diffusion layer act as a protective layer and stops the transfer of electron across the junction when equilibrium is reached. When solar energy is imposed the energy of electrons available will increase and again transfer of electron get start. This will cause flow of current and convert solar energy into electric energy. 7. MATLAB MODELLING OF PV ARRAY - The equivalent circuit implementation of PV cell is shown in fig editor@iaeme.com

4 S. D. Pagare and A. K. Jhala Figure 1 To simulate PV array first of all module of PV array is to be develop. For minimizing the shading effect the series connected PV modules with the same level insulation makes subassembly. To make large array several such series-connected subassemblies are connected where each will have same level of insulation. Series assemblies, whose shading pattern is similar form a group. Such various group are get connected in parallel to form a complete PV-array. The I-V and P-V characteristics of the various components of such PV array is given in Table I [4]. Group Table 1 Shaded Pattern and Configuration [4] Number of unshaded Modules in series assembly (λ=1) Number of shaded Modules in series assembly (λ=0.1) Number series assemblies in a group G G G Figure 2 PV Array 4 editor@iaeme.com

5 Use of By-Pass Diode in Maximum Power Point Tracking System Figure 3 PV Array with bypass and blocking Diodes 8. EFFECT OF BYPASS AND BLOCKING DIODES ON PV CHARACTERISTICS As mentioned in Fig-3 a PV array with bypass and blocking diodes connected in the array. It is important to note that the characteristics of and array with bypass and blocking diodes connected in the array. It is important to note that the characteristics of an array with bypass and blocking diodes differ from that of an array without these diodes. 9. CONCLUSION The shading effect is major cause of multiple peaks problem in PV-array system. The above given study is an attempt to discuss various cause and throes of this multiple peaks problem. In the Bypass and Blocking diode based MPPT scheme this problem can be overcome up to certain extent. The I-V and P-V characteristics of PV array having series and parallel combinations of modules. The study reveals that the magnitude of global peak depend on the pattern in which modules are connected and the pattern of shaded cells in each module. REFERENCES [1] Samer Said, Ahmed Massoud, Mohieddine Benammar and Shehab Ahmed, A Matlab/Simulink-Based Photovoltaic Array Model Employing Sim Power Systems Toolbox Journal of Energy and Power Engineering 6 (2012) [2] M. A. Younis, T. Khatib, M. Najeeb, A. M. Ariffin, An improved maximum power point tracking controller for PV systems using artificial neural network, Przegląd Elektrotechniczny, CA: Wadsworth, vol. 88, no. 3b, pp , [3] T. Esram, P.L. Chapman, Comparison of Photovoltaic Array Maximum Power Point Tracking Techniques, IEEE Transactions on Energy Conversion, vol. 22, no. 2, pp , June [4] Hiren Patel and Vivek Agarwal, MATLAB-Based Modeling to Study the Effects of Partial Shading on PV Array Characteristics, IEEE Transactions On Energy Conversion, VOL. 23, NO. 1, MARCH [5] E. Koutroulis, K. Kalaitzakis, and N. C. Voulgaris, Development of a microcontroller-based photovoltaic maximum power point tracking control system, IEEE Trans. Power Electron., vol. 16, no. 1, pp , Jan editor@iaeme.com

6 S. D. Pagare and A. K. Jhala [6] V.Quaschning and R.Hanitsch, Numerical simulation of current voltage characteristics of photovoltaic systems with shaded solar cells, Solar Energy, vol. 56, no. 6, pp , Feb [7] H. Kawamura, K. Naka, N. Yonekura, S. Yamanaka, H. Kawamura, H. Ohno, and K. Naito, Simulation of I V characteristics of a PV module with shaded PV cells, Solar Energy Mater. Solar Cells, vol. 75, no. 3/4, pp , Feb [8] Samer Said, Ahmed Massoul,Mohieddine Benamma1 and Shehab Ahmed A Matlab/Simulink-Based Photovoltaic Array Model Employing SimPowerSystems Toolbox Journal of Energy and Power Engineering 6 (2012) [9] Prof. Sharwan Kumar Jhajharia. A Comparative Study of Diode and Thyristor Converters used in the Aluminum Smelters. International Journal of Electrical Engineering & Technology, 4(6), 2013, pp editor@iaeme.com