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Ulusal şebekeye bağlı güneş pili sistemlerinin modellenmesi ve gerçeklenmesi

Başlık çevirisi mevcut değil.

  1. Tez No: 66596
  2. Yazar: SEZGİN PARMAKSIZ
  3. Danışmanlar: DOÇ. DR. METİN GÖKAŞAN
  4. Tez Türü: Yüksek Lisans
  5. Konular: Bilgisayar Mühendisliği Bilimleri-Bilgisayar ve Kontrol, Computer Engineering and Computer Science and Control
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1997
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Bilgisayar Mühendisliği Ana Bilim Dalı
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 125

Özet

ÖZET Bu çalışmada ulusal şebekeye bağlı bulunan üç farklı güneş pili sistemi incelenmiştir. Bu sistemler güneş pili, evirici, filtre ve transformatörden oluşmuş olup, güneş pillerinden elde edilen doğru akım biçimindeki enerjiyi alternatif akıma dönüştürerek senkron olarak şebekeye aktarmak için kullanılırlar, incelenen sistemler PSPICE 'da simüle edilerek eviricilerin çalışması incelenmiş, eleman değerleri belirlenmiş ve elde edilen çıkış dalgalan üzerinde gerekli analizler yapılmıştır. Ayrıca, benzer modellerle karşılaştırıldığında oldukça küçük hataya sahip olan simülasyon amaçlı yeni bir güneş pili modeli geliştirilmiştir.

Özet (Çeviri)

SUMMARY Each and every society's capability of development, or indeed its ability to survive, depends on continuing access to energy in appropriate forms and quantities, and at acceptable levels of costs (Cook, 1976). There is a relationship, which changes over time, between the degree of development in a society (economy) and the use of energy. This illustrated in Fig. 1. Until recently (when a small number of wealthy and highly industrialized countries have started to use less energy), this relationship has been one an increasingly intensive use of energy as development proceeded. Thus the gradual transformation of the world over the last 200-plus years, from a world in the mid-eighteenth century made up largely of primitive and peasant societies which were largely subsistence in their structure and organization to a world now consisting mainly of post-industrial, industrial and industrializing economies, has led HIGH A us The U.S. moved on to this flatter part of tie curve after 1950 and other industrial countries after 1973 Host »estern European countries and Japan transferred from points B/B' (high rates of Increase In energy use) to point C {loner rates of Increase ) between 1950 and 1973 Host developing countries nave moved onto this sector (A/A'} of the carve since the 1950's and nay be expected“to continue to have high rates of increase in energy demand : but note that recent higher prices have; no» reduced the rates of growth '^- Industrialised countries now have have a slov rate of growth in or a Reduced use of energy with environmental constraints and improved efficiency of energy use under higher price conditions Very few under-developed countries remain on tMs section of the curve with only low rates of increase in energy use rHDUSTRIAL PEBIOD. BERIOD OE IHDUSTItlALISHIC! DEVELOEWENT OVER IDE * POST INDUSTRIAI, SOCIETIES> Fig. 1 The Relationship between Energy Use and Economic Development : the rate of increase(decrease) in energy use is a function of the stage of economic development to a global use of energy which is now 20 times greater than its estimated to have been in 1860- the earliest date for which world energy use can be estimated with any degree of confidence (Marchetti and Nakicenovic, 1979). XVThe sun is responsible for most of the earth's energy in one way or another. Plant photosynthesis provided the basis of our fossil fuels such as coal and oil. Heat from the sun and specifically its effect on weather patterns, is indirectly responsible for that other common form of renewable energy, wind power. Solar power, in its accepted working definition, is the supply of energy directly from the sun. It is essentially made up of two very distinct technologies, solar thermal and solar photovoltaics. The first technology is based on the principle of using the sun's direct heat energy and is most commonly used for supplying hot water for houses and swimming pools. However, it is photovoltaics which is of interest here. This is a technology where the light from the sun is converted directly into DC electricity. The photovoltaic effect - the conversion of light into electricity - was first noticed over 150 years ago by the French scientist Becquerel. He observed a light dependent voltage between two electrodes immersed in an electrolyte. Further practical application of this work had to wait until the acceleration of the space programme during the late 1950s. Solar power electric power became the only viable energy source for orbiting satellites, despite its initial high costs. Any fuel carried would have only a limited life and the more fuel carried the larger the initial weight, in turn requiring more fuel to send the device into space. The satellite programme therefore provided the initial impetus in the use of solar electric power supplies and formed the basis of the technology used in today's terrestrial applications. In the 1980s there came a greater public awareness of the environmental costs of traditional energy generation. These issues came to the fore adding fresh impetus. Pollution and global warming became issues discussed by heads of government. Solar which emits no carbon dioxide, sulfur or nitrous oxide emissions offered one potential avenue to alleviate the inevitable consequences of global wanning. The main benefit of solar power system is their use of ”free" fuel from the sun, resulting in only minimal running costs. Equally important for users is the minimal maintenance requirement, with the critical element, the solar modules having no moving parts. Indeed examples of life-cycle costing show a strong advantage when compared to diesel generators or even in some cases the electricity grid system, when maintenance costs are taken into consideration. The basic component of any solar electric system is the solar cell, which, using a simple analogy, operates in a manner similar to a diode. The principal raw material silicon is intensely refined to remove all the unwanted impurities. Half is then doped with boron which has excess positive electrons and half with phosphorus which has excess negative electrons. When light energy (photons) falls on the front surface of the cell, an excess of energy results in the movement of electrons between layers exactly in a P-N junction diode. This then collected, by a metal backplate and grid on the cell, as electricity. A model of photovoltaic cell is important for simulation of photovoltaic systems. The new model for modeling photovoltaic cell which is based on equivalent electrical circuit approach is developed. The new model is shown in Fig. 2. xviFigure 2 The New Model of Photo voltaic Cell The current-voltage characteristic of the model for nominal conditions (600W/m\ 25 °C) is given in Fig. 3. The error of the model is about 0.02. 10 15 vrv] 20 25 Figure 3 Simulations and Measurements Results for Nominal Conditions There are two basic types of solar power system. Most common are self contained power systems. In the developed world however increasingly important are so-called grid-connected systems. These are subtly different as they work with rather than instead of the electrical grid. Where solar is used as the only power supply system the remaining elements of a complete solar electric power system are specifically designed batteries to store energy and thus ensure continuity of power supply when the sunlight is insufficient either during the night or period of poor weather e.g. heavy cloudcover, and a charge XVllcontrol unit to create an effective and efficient battery charging regime between the solar modules and batteries. Grid connected systems do away with the need for batteries. In these systems the solar panels are simply interconnected via safety equipment and an inverter to grid (subjected to local legislation). When more power is required than the solar panels can provide the grid supplements this. At other times (again subject to regulation) the solar panels may contribute to grid when more power is produced than used. Utility interactive residential photovoltaic systems offer the advantage, with regard to systems using batteries, of overcoming the problem of energy storage through injection of the photovoltaic power by means of an electronic inverter directly into the utility grid. Such an inverter should produce a sinusoidal current with low harmonics and should perform with high efficiency over a large of input power and voltage. Most of the inverters for photovoltaic applications discussed in the literature have been modifications of existing conversion equipment. Two type of systems have been proposed, the current-fed line-commutated thyristor inverter and the voltage-fed forced-commutated inverter. The technological advances in semiconductor switching devices, dc-capacitor and ferrite-cored inductivity have made possible the realization of new types of inverters with high-frequency switches. The resulting circuits show significantly better performances such as higher efficiency especially at lower power levers, lower harmonic distortion, and reduced weight and volume as compared to conventional inverters. ARRAY M? r= i1 - 1.? I* I I' wm Figure 4 Utility Interactive Power Converter with High- Frequency Transformer Fig.4 shows such a system which use high-frequency link converter, to convert variable dc voltage of the photovoltaic array into constant ac voltage which is in phase with utility. In this system, a high-frequency PWM inverter feeds a high- frequency isolation transformer with a sinusoidally shaped current. The output of the transformer is rectified with diode bridge rectifier. Four thyristor, used as 50-Hz switches, reverse the polarity of the rectified current on every other half-cycle of the utility voltage. This reversal is accomplished slightly before the natural zero crossing of the voltage, thereby providing commutation for the thyristor. Sample computer simulation result is given in Fig.5 XVUl48A- -4M + ? I(usabs) 20ns Time Figure 5 Line Current XIX

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