Dağıtım şebekelerinin PSO kullanılarak yeniden yapılandırılması
Reconstruction of distribution networks using PSO
Yazar: ASLI ÇAKIR
Danışman: DR. ÖĞR. ÜYESİ HATİCE LALE ZEYNELGİL
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Elektrik Mühendisliği Ana Bilim Dalı / Elektrik Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2019
Konu: Elektrik ve Elektronik Mühendisliği = Electrical and Electronics Engineering
Dizin: Elektrik dağıtım sistemleri = Electric distribution systems

Özet:
Dağıtım sisteminde genel olarak endüstriyel, ticari, konut ve aydınlatma yükleri bulunmaktadır. Şebekedeki trafolar ve hatlar günün pik saatlerinde ağır yüklenirken diğer saatlerde hafif yüklenir. Bu, şebekenin çalışma koşulları için zararlıdır ve yüksek oranda güç kayıplarına ve düşük gerilim profiline yol açar.
Şebekedeki bu değişken durumdan en az etkilenebilmek için gün içinde yüklerin optimal olarak dağıtılması önem taşır. Şebeke yeniden yapılandırılarak ağır yüklenmiş hatların yükleri, hafif yüklenmiş hatlara aktarılır. Bunun sonucunda, şebekedeki kayıplarda azalma yaşanırken baraların gerilim seviyesi de yükseltilmiş olur. Her yük enerjilendirilmek koşuluyla, şebekede bulunan anahtarların açık/kapalı durumunun değiştirilmesiyle şebeke yeniden yapılandırılmış olur.
Güç sistemlerinde kullanılan optimizasyon türleri, bir objektif fonksiyonun minimum ya da maksimum değerini bulmayı amaçlar. Gauss-Seidel yöntemi, Newton Raphson yöntemi gibi geleneksel yöntemler; doğrusal, sürekli ve diferansiyel özellikli amaç fonksiyonlarını çözmek için kullanılır. Doğrusal olmayan amaç fonksiyonlarını çözmek için, evrimsel algoritmalar ortaya atılmıştır. Evrimsel algoritmalar doğrusal olmayan problemlerin optimizasyonu için kullanılan rassal ve güçlü algoritmalardır. Bu evrimsel algoritmalar arasında, parçacık sürüsü optimizasyonu (PSO) algoritması da şebekenin yeniden yapılandırılmasında sıklıkla kullanılan bir algoritma olmuştur.
Bu tez çalışmasında PSO algoritması ile şebeke yeniden yapılandırılmıştır. Algoritmanın amaç fonksiyonu şebekedeki aktif güç kaybının en düşük olduğu anahtar kombinasyonunu bulmaktadır. Belirlenen kısıtlamalara uygun olarak bulunan yeni şebeke yapısına göre, şebekedeki kayıplar büyük oranda azaltılmış, şebekenin gerilim profili iyileştirilmiştir.
Tezde geliştirilen algoritma literatürde sıkça kullanılan iki test şebekesi üzerinde denenmiş, sonuçlar; algoritmanın yetkinliğinin kanıtlanması için, sunulan diğer çalışmalar ile kıyaslanmıştır. Yapılan karşılaştırma sonucunda, geliştirlen algoritmanın diğer çalışmalara kıyasla daha iyi sonuçlar verdiği ve kayıpları daha çok azalttığı gözlemlenmiştir.
Sürekli artan enerji talebine karşı insanlar daha temiz enerji kaynaklarına yönelmeye başlamıştır. Fosil yaktıların yakın zamanda tükenebilecek olması ve çevreye verdiği zararlar bu olayı hızlandırmıştır. Son zamanlarda kullanımı artan dağıtık üretim tesislerinin şebekeye etkisini incelemek için, uygun baralara optimal boyutlarda dağıtık üretim üniteleri eklenmiş ve şebeke yeniden yapılandırılmıştır. Şebekede hem aktif hem de reaktif güç kaynaklarının etkisini gözlemlemek için şebekeye, dağıtık üretim ünitelerine ek olarak kapasitör grupları da eklenmiş, şebeke yeniden yapılandırılmıştır.

Abstract:
The distribution network generally includes industrial, commercial, residential and lighting loads. Transformers and feeders in the network are loaded with heavy loads during the peak hours of the day while other hours are lightly loaded. This is harmful to the operating conditions of the network, resulting in high power losses and a low voltage profile.
In order to be least affected by this variable situation in the network, it is important to distribute the loads optimally during the day. The network is reconfigured and the loads of heavily loaded lines are transferred to lightly loaded lines. As a result, the voltage level of the buses is increased while the losses in the network are reduced. The network is reconfigured by changing the on / off status of the switches in the network, provided that each load is energized.
The optimization types used in power systems aim to find the minimum or maximum value of an objective function. Conventional methods such as the Gauss-Seidel method and the Newton Raphson method are used to solve linear, continuous and differential-specific objective functions. Evolutionary algorithms have emerged to solve nonlinear objective functions. Evolutionary algorithms are random and powerful algorithms for the optimization of nonlinear problems. Particle swarm optimization (PSO) algorithm has also been used frequently in the reconstruction of the network among these evolutionary algorithms.
In this thesis, particle swarm optimization algorithm has been used in the network reconfiguration to minimize power losses and to improve the voltage profile in the distribution network.
Particle swarm optimization was first introduced by Kennedy and Eberhart as a new heuristic method. Algorithm is inspired by the social behaviors of flocks of birds and fish. Unlike many traditional techniques, it is a non-derivative algorithm. There are fewer parameters for editing than other competitive evolutionary algorithms, thus it is easy to implement and program. Good selection of parameters has a significant impact on the performance of the PSO algorithm.
In this thesis, the network was reconfigured with PSO algorithm. The objective function of the algorithm finds the switch combination with the lowest active power loss in the network. According to the new network topology in accordance with the determined constraints, the losses in the network have been greatly reduced and the voltage profile of the network has been improved.
The algorithm developed in the thesis was tested on two test networks frequently used in the literature, and the results were compared with other studies presented to prove the competence of the algorithm. As a result of the comparison, it was observed that the developed algorithm gave better results compared to other studies and decreased the losses more.
With increasing demand for power, the trend towards renewable energy sources such as solar, wind, biogas and fuel cells has begun and the energy produced from these sources has increased in recent years. Distributed generation (DG) is a new approach in the energy industry and there are many definitions of this concept. Some countries define distributed generation on the basis of voltage level, while others define DG based on the technology used (renewable, cogeneration) or location.
Distributed generation is generally close to consumption point; it is defined as the use of small, modular electricity generation as integrated or stand-alone. The International Council on Large Power Systems (CIGRE) workgroup defines DG as all production units with a maximum capacity of 50 to 100 MW, usually connected to the distribution network.
In addition to environmental benefits, DGs contribute to the implementation of competitive energy policies, diversification of energy resources, reduction of operating costs, postponement of network renewal, reduction of losses and transmission-distribution costs, and potential increase of service quality. DG reduces overloading of existing electrical equipment, thus, minimizes their maintenance costs and increases their service life. DGs improve the network's voltage profile and reduce the number of voltage regulators and capacitors required and minimize their maintenance costs. In addition, DGs are available in modular units that require less space for smaller manufacturers, shorter construction times, and lower capital costs.
In order to examine the effect of the recently used distributed generation on the grid, distributed generation with optimal sizes have been added to the appropriate buses and the network has been reconfigured. The results show that distributed generation is an effective way to minimize power losses and improve the voltage profile of the distribution network.
Capacitors are now generally used for compensation. The cost of the capacitors is much lower compared to DG. There are two types of capacitors; switched and fixed. Switched capacitors, though more expensive in terms of cost, have a more advantageous position in the future, considering the loads that can be added to the network. Thus, the switched capacitor stage is changed instead of adding a capacitor at a time.
Benefits provided by capacitors that are providing reactive power to the grid:
Increase the voltage in the buses
Reduce network losses
Reduce the load on the lines
Increase the power factor (cosφ) value
In order to observe the effect of both active and reactive power sources in the network, capacitor groups were added to the grid in addition to the distributed generation and the network was reconfigured.
The PSO algorithm developed for this thesis was applied to IEEE 33 and 69 bus radial network test systems to solve the problem of network reconfiguring. In order to observe the effects of increasingly distributed generation and capacitor groups, they are also placed in the most suitable buses.
In the thesis, MATLAB 2016a program is used for PSO algorithm and MATPOWER developed by Ray Zimmerman is used for power flow of distribution network.
As a result, the application results showed that network reconfiguration is an effective and widely used method to reduce power loss and improve the voltage profile. It has also been found that the optimally sized and placed distributed generation and capacitor groups, when used together in the network, reduce system losses more. In this study, three methods for reducing power losses have been combined and the results are truly encouraging.