FV sistemlerde güneşi takip eden sistem tasarımı ve MPPT kontrolü ile enerjinin yüke maksimum olarak aktarılması
Designing smart solar tracker for PV systems and transfering energy to the load with MPPT
Yazar: MUHAMMED İKBAL ORT
Danışman: YRD. DOÇ. DR. TUFAN KUMBASAR
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Kontrol ve Otomasyon Mühendisliği Ana Bilim Dalı / Kontrol ve Otomasyon Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2016
Konu: Elektrik ve Elektronik Mühendisliği = Electrical and Electronics Engineering
Dizin: Motor kontrol = Motor control ; PD kontrol = PD control ; PID = PID ; Yenilenebilir enerji = Renewable energy

Özet:
Özellikle son 20 yılda teknolojinin ve sanayinin gelişimine bağlı olarak enerji ihtiyacı artarak devam etmektedir. Bu ihtiyacı karşılamak için birçok farklı kaynak kullanılmaktadır.

Fosil yakıtlar, enerji ihtiyacını karşılamak için geçmişten günümüze kadar en yaygın kullanılan enerji kaynağı olmuştur. Halen birçok ülkenin başlıca enerji kaynağı olmasına rağmen, doğaya saldıkları zehirli gazlar ve çevreye verdikleri zarar sebebiyle önemi gittikçe azalmaktadır. Fosil yakıtların kullanımının azaltılmak istenmesine rağmen enerji ihtiyacının önemli bir oranda artmaya devam etmesi, bu enerji ihtiyacının farklı kaynaklardan teminine zemin hazırlamıştır.

Son yıllarda, yenilenebilir enerji kaynaklarının kullanımında önemli ölçüde artış gözlenmiştir. Bu kaynaklar içerisinde en önemli yenilenebilir enerji kaynağı, şüphesiz güneştir. Güneşe ulaşılabilmesinin kolay olması yanında yeryüzünde bulunan bütün enerji kaynaklarından daha fazla potansiyel enerji barındırması, güneşi yenilenebilir enerji kaynakları içerisinde ilk sıraya yerleştirmiştir.

Güneş enerji sistemlerinin maliyetleri azalan bir eğilim göstermesine rağmen hala yapılan yatırımların geri dönüş süresinin uzun olması ve atmosferik koşullardan kaynaklı bazı olumsuz durumlardan dolayı, güneş enerjisi sistemlerinde bulunduğu koşullar altında üretebilecekleri maksimum enerjiyi üretmeleri ve bu enerjinin kayıpsız bir şekilde kullanılacağı yüke aktarılması büyük önem taşımaktadır. Bu tez çalışmasında da bu konular ele alınmıştır.

Öncelikle güneş enerjisinin potansiyeli, ülkemiz ve dünyadaki kurulu sistem güçleri verilerek güneş enerjisinin ne denli önemli bir enerji kaynağı olduğu vurgulanmıştır.

Sonrasında güneş enerjisinden elektrik üretmekte kullanılan fotovoltaik hücre ve panel yapıları verilerek matematiksel olarak bu yapıların modelleri oluşturulmuştur.

Sonraki bölümde ise güneşi takip eden fotovolatik bir sistemin tasarımı yapılarak, bu sistemin kontrolü PID kontrolör ile yapılmıştır. Bu bölümde kullanılan radyasyon verileri, geçmiş yıllara ait gerçek radyasyon verileridir.

Son olarak fotovoltaik sistemler yardımıyla üretilen enerjinin yükse maksimum olarak aktarılmasını sağlayan maksimum güç noktası takipçisinin dört farklı yöntemler tasarımı yapılmış ve bu sistemlerin birbirine göre avantajları ve dezavantajları verilmiştir.

Her bir bölümde modellemesi yapılan sistemlerin MATLAB/Simulink yardımıyla simülasyon modelleri oluşturulmuş ve çalışma içerisinde verilen koşullar altında simülasyonları yapılmıştır. Maksimum güç noktası takipçilerinin simülasyonundan elde edilen veriler karşılaştırılarak en iyi sonucu veren sistemler belirtilmiştir.

Abstract:
Especially in last four decades, due to development of technology and industry, the need of energy continues to increase by the time. An there many resources to produce energy from. But most of them are harmful for environment to use for producing energy.

Fossil fuels are very common energy sources for producing energy form the past until now. Still most countries' number one energy resources are fossil fuels in despite of releasing greenhouse gases in very large amounts. 

Most used energy resource is coil in the world. Because it is easy to produce and cost of it is more less when compare to other resources. But the damage is enormous for the environment. But usage of coil and other fossil fuels is decreasing slowly by time with countries taking action for toxic contaminant these fuels produces. 

However, there is still remaining one problem to supply increasing energy need when these fuels' usage is decreasing. For that, countries and entrepreneurs search for other supplies for energy like renewable energy sources. 

Renewable energy sources have an increasingly important for producing energy generation in last two decades. Besides reducing the depending on fusel foils, also they reduce the emission of greenhouse gases. Some of renewable energy resources are solar energy, wind power, hydropower, geothermal energy and bio energy. While these renewable energy resources other than solar energy strongly depends on some conditions like location, athmospheric conditions and large areas, the only basic need for solar energy is sun.

The most important renewable energy source is solar power with no doubt. Besides being easy reachable, having potential energy more than other renewable sources makes solar energy most important green energy. Also because of its ubiquity, abundance and sustainability, solar energy is the most essential source among the other renewable energy sources.

A variety of technologies convert sunlight to usable energy for buildings. The most commonly used solar technologies for homes and businesses are solar water heating, passive solar design for space heating and cooling, and solar photovoltaics or using mirrors and boilers for electricity.

For producing electricity from sun, photovoltaic cells/panels are most common method among the others. Photovoltaic cells convert light into electrical direct current by taking advantage of the photoelectric effect. Many of solar photovoltaic cells form photovoltaic panels to produce more energy. And by connecting these panels in series or parallel, energy production in big scales like Megawatts or Gigawatts is satisfied.

Producing energy by photovoltaic panels are consisted of some methods like fixed mounted photovoltaic panels or photovoltaic panels using solar trackers. For fixed mounted systems, panels are mounted on steel construction materials with a fixed angle to the sun's trajectory. This angle depends on system's location on earth. For instance, while a system on ecuador line has $ 0^\circ $ angle with the surface of earth, in Turkey this angle must be around $ 25^\circ $ to produce more energy.

For the systems shich track the sun's trajectory, there are several methods. One of them is passive solar trackers. This method based on thermal expansion of matter. When the two tracker which makes the panel move expose to the sun within different time line, the most heated tracker makes the system move towards to it.

The other basic system to track the sun is active solar tracker. These systems include motor, motor driver, sensors and control units with appropriate contruction for moving. In these systems, generally, the information which comes from sensors evaluates in control unit and by that motor is controlled to track sun trajectory. 

Over the years, reserchers have proven that smart solar trackers maximize the energy prodeced from solar systems. In many research, solar trackers' performance has compared to fixed solar systems. And it is shown that there is an increase between $ \%20-\%50 $ at produced energy in solar systems with solar tracker compared to fixed systems.

For photovoltaic panels or systems, there is a certain point for output that power is maximum at. While considering the difficulties for producing the electricity from solar systems, it is significant to make system at this point without a loss. 

When a photovoltaic panel connects directly to the load, output of panel will work rarely at the maximum power point and it will not be optimal.

Many reserch proposed new methods or a development in an existing method for transferring energy from PV panel to load. They are called "Maximum Power Point Tracker - MPPT" mainly. Their aim is to find which point PV cell/array produces maximum energy and make load to have same energy via DC-DC converters.

The costs of solar energy are decreasing slowly by time. However, it is still not cheap and for some negative effects originating from atmospheric circumstances, to produce maximum energy that PV systems can produce under existing conditions and to transfer this energy to the load with no loss brings forward. For that this thesis aims to examine producing maximum energy from solar systems and transfer it to load without loss.

In the first chapter, some information about potential of solar energy on earth's surface has been given. To give an opinion to reader, a table is created for installed solar energy in some countries. As reader will see in this chapter, installed solar energy capacity grows year by year. Every country makes investments in solar energy. For Turkey, it is growing in a big percentage. In 2014, installed solar energy for Turkey was almost $ \%90 $ of the all capacity. 

After that, physical structure of PV cell and array that produces electricity from solar irradiation has been introduced. Also equations for PV solar cell are given and by that a mathematical model for PV cell and array is created. At the end of this chapter, a MATLAB/Simulink model has developed and for different irradiations and temperatures, this model simulated for a real PV array specifications based on its datasheet.    

In third chapter, solar tracker systems have been introduced. Firstly different types of solar trackers are given. Later a smart solar tracking system with two light dependent sensor and a DC motor with PID controller is designed. To specify PID controller parameters, a tool which MATLAB/Simulink PID Tuner provide is used. In simulation part, the system simulated for tracking sun and compared to fixed panels with $ 45^\circ $, $ 90^\circ $ and $ 135^\circ $. Irradiation on PV panel's surface is found more with solar tracker system. It has shown by a graph.

In fourth chapter, first some general information is given for different types of MPPT techniques. Their advantages and disadvantages are given for whom think to design an MPPT for a PV system to keep in mind. After that, four different MPPT structure is given and modelled in MATLAB/Simulink. Their performances for different system parameters such as irradiation at different levels, sudden change in irradiation are evaluated via simulation and two systems that produce best performance are given in last section.

Finally in the last chapter, a comparison has made for simulated systems both in third and fourth chapters. For sun tracking systems, results evaluated in the manner of irradiances which obtained from fixed PV systems and PV systems with solar tracker. After that for different MPPT methods which has been simulated in fourth chapter are compared. Two MPPT methods which gave the best result are inroduced. A table is created for comparison MPPT models.