Simulation of PV array with Partial Shading Effect
An array of solar panels is the most efficient and reliable way to harness renewable energy. Not only does it not pollute the environment, but it also requires no upkeep, can be reused, and has no finite end. The primary factors influencing a photovoltaic system's output are irradiation, module temperature, and array arrangement. Knowing how shading impacts the PV array's output power is vital for ensuring the system functions effectively. Partial shading happens when there is a difference in the amount of light reaching each module in an array. This shadow might be easy to forecast or hard to predict depending on circumstances such as the proximity of the next building, a nearby tree, clouds, or a building. Our purpose here is to use MATLAB to explore and show how partial shading works.
Keywords: PV system; partial shading; bypass diode; the I-V and P-V characteristics
The use of renewable energy sources is crucial for the production of power. Electricity and other useful forms of energy will be produced and supplied from a variety of renewable resources, including wind, solar, geothermal, ocean thermal, and biomass . Photovoltaic solar power, one kind of renewable energy, is becoming popular because of its low initial investment and almost infinite supply. Compared to other renewable energy sources, photovoltaic power systems are superior since they do not include mechanical or moving components . There is widespread recognition and utilization of EPV system applications in the power technology industry at present. Alternative energy production, solar vehicle building, battery charging, water pumping, and a satellite grid are just a few of the many promising future uses of today's technology.
In order to convert solar energy into electricity, a photovoltaic power system relies on photovoltaic modules, also known as solar panels . The PV array is susceptible to shade from several factors, such as changing clouds, tree canopies, surrounding buildings, dirt, rubbish, bird droppings, slants, and more. When the PV array is partially or completely shaded, the output I-V characteristics diverge from linearity, causing many local maxima on the P-V curve and a decrease in output power. While shading can limit power output, it also causes hotspots that may damage PV module cells. Cells that are in the dark are subject to less heat stress thanks to a bypass diode that has been plugged in.
The effects of shadow vary with the kind of module, where the bypass diodes are located, how the strings are set up, and how intense the shade is. Shade, insufficient grounding, and voltage mismatch between parallel PV strings are all causes of power loss . The behaviour of a solar array when exposed to partial shadowing was reviewed and evaluated in MATLAB [5, 6], . Solar photovoltaic (PV) modules in series and parallel configurations were tested, and the negative impacts of partial shade were evaluated. In this work, we show how to run a simulation based on a fixed model. In this investigation, we focus on the PV array's performance characteristics as they relate to various degrees of shade.
II. PARTIAL SHADING EFFECT ON SOLAR CELLS
The shading of PV panels by nearby buildings or trees, air currents, the presence of clouds, and the ever-shifting sun's zenith angle make constant, even lighting impossible. Shade, current mismatch within a PV string, and voltage imbalance between parallel strings all contribute to power loss. Crystalline silicon modules often use bypass diodes to protect partly shaded cells from damaging reverse bias .
A cell may be thought of as a diode with a current generator. The photocurrent flows opposite to that of a diode. In other words, if one cell in a string is partly shaded, it will create less current than the others, and the other cells will attempt to force more current through the poor cell than the poor cell provides. However, this can't happen since it would turn the cell into a diode operating in the opposite direction. Thus, the current in the string will be capped by the current generated in the weak cell .
To counteract this effect, a bypass diode is placed across a selected sequence of cells (ideally we should use one bypass diode across each cell, but it is not feasible). The current can only travel in one direction via a bypass diode. A parallel-connected bypass diode provides a low-resistance channel for power that is being dissipated into the sink. This eliminates issues like hotspots and shield cracking by preventing power loss in the panel. [10–11].
III. EFFECT OF BYPASS DIODES ON PV CHARACTERISTIC
To lessen the effects of shadowing on the P-V and I-V curves of a PV module, it is common practice to utilise a bypass diode in parallel with a string of cells. Three cells are linked in series with bypass diodes in parallel. Bypass diodes are reverse biassed and each cell produces electricity under normal circumstances when no shading impacts the PV-module. In contrast, when a cell is covered, the diode across from it will begin conducting, allowing electricity to flow across the covered area.
IV. SIMULATION RESULTS
This study compared the I-V and P-V characteristics of a solar array under partial shadowing with and without a bypass diode. The MATLAB software was used to model the system, and the results shed light on how much of an impact partial shade has on a PV array (array). Previous studies have shown that photovoltaic systems are particularly vulnerable to the effects of partial shade.
Partial shadowing may have a significant impact on the maximum power output of a solar system. How vulnerable a solar system is to partial shadowing depends on factors such as the intensity and distribution of shade, as well as the wiring layout used to link the individual photovoltaic modules. The bypass diode is crucial to the proper operation of the solar system in a variety of partially shaded environments. Our understanding of how shadows affect solar panels may be improved with this research. For this reason, we must find a way to lessen its effect.
 S. Pachpande, P. Zope, "Studying the effect of shading on solar panels using MATLAB," ISSN N° 2278-3083, Volume 1, No. 2, June 2012.
 J. Teo, R. Tan, V. Mok, V. Ramachandaramurthy, and C. Tan, "Impact of Partial Shading on the P-V Characteristics and the Maximum Power of a Photovoltaic String," Energies 2018, 11, 1860, July 2018.
 G. Sreenivasa, T. Bramhanada, and M. Vijaya, "A Matlab based PV module model analysis under conditions of nonuniform irradiance," Energy Procedia 117, 974–983, 2017.
 N. Nagaraja1, T. Gowri, "Study on Performance Characteristics of PV Arrays under Non-Uniform Irradiation Conditions," ISSN (Online) 2393-8021, Vol. 3, Issue 11, November 2016.
 A. Bouraiou, S. Lachtar, A. Hadidi, and N. Benamira, "Matlab/Simulink Based Modeling and Simulation of Photovoltaic Array Under Partial Shading," ISSN: 2356-5608, Sousse, Tunisia, 2014.
 X. Nguyen, "Matlab/Simulink Based Modeling to Study the Effect of Partial Shadow on Solar Photovoltaic Array," "Nguyen Environ Syst Res, 2015.
 L. Fialho, R. Melicio, V. Mendes, J. Figueiredo, and M. Collares, "Effect of Shading on Series Solar Modules: Simulation and Experimental Results," Procedia Technology 17, 295–302, 2014.
 S. Dezso, B. Yahia, "On the Impact of Partial Shading on PV Output Power," "RES'08 WSEAS, September 2018.
 Chaudhary, S. Gupta, D. Pande, F. Mahfooz, and G. Varshney, "Effect of Partial Shading on characteristics of PV panels using Simscape," ISSN: 2248-9622, Vol. 5, Issue 10, (Part – 2), pp.85–89, October 2015.
 W. Tiampei, "Study on maximum power point tracking of a photovoltaic array in irregular shadow," International Journal of Electrical Power & Energy Systems, vol. 66, pp. 227-234, 2015.
 A. Maki and S. Valkealahti, "Effect of photovoltaic generator components on the number of MPPs under partial shading conditions," IEEE Trans. Energy Convers., vol. 28, no. 4, pp. 1008–1017, Dec. 2013.