Low-frequency oscillations due to unpredictable disturbances in an interconnected power grid are a serious threat
to the stability of the power system. Reliable operation of a modern power system, when exposed to sudden
disturbances, is crucial, and the safe operation of the system is directly related to success in damping oscillations.
Power System Stabilizer (PSS) devices have been used to reduce fluctuations caused by short-time disturbances
in power systems. These devices provide additional damping torque components to the generators as an auxiliary
control device of the excitation system. Due to the non-linearity of electrical power systems, it is significant to
design multi-machine power systems with optimum PSS parameters under critical conditions. In this paper, the
PSS design problem was solved using the Runge Kutta Algorithm (RUN). The PSS design problem was considered
an optimization problem in which an eigenvalue-based objective function has developed, and the proposed RUN
method was tested in a WSCC 3-machine 9-bus test system using the linearized Heffron-Phillips model. In the
linearized model, system stability has been enhanced by shifting the eigenvalues to the stability regions. When the
results obtained from the test system are examined, it has seen that the proposed RUN is the most effective method
in terms of system stability.
|
Bu çalışmada, iki bölgeli ara-ısıtmasız termal güç sistemi ile çok kaynaklı güç sistemlerinin yük frekans kontrolü (YFK) ele alınmıştır. Bu sistemlerde ikincil denetleyici olarak basit yapılı PID denetleyicisi tercih edilmiştir. Denetleyici performansını artırmak amacıyla yeni bir hedef fonksiyonu tasarlanmış ve bu hedef fonksiyonunun değeri simbiyotik organizmalar arama algoritması (SOAA) ile azaltılarak PID denetleyici parametreleri elde edilmiştir. Benzetimi gerçekleştirilen tüm elektrik güç sistemleri MATLAB/Simulink ortamında modellenmiş, optimizasyon tekniği ise MATLAB/M-file ortamında kodlanmıştır. Çalışmanın literatüre katkısının ispatı için her bir güç sisteminden elde edilen sonuçlar iyi dergilerdeki popüler sonuçlarla karşılaştırılmıştır. Karşılaştırma sonuçlarına göre önerilen hedef fonksiyonu ile ayarlanan SOAA:PID denetleyicinin, basit yapısına rağmen, frekans ve bağlantı hattı güç değişim eğrilerindeki salınım (oscillation), oturma zamanı (settling time), maksimum pozitif aşım (maximum overshoot) ve maksimum negatif aşım (maximum undershoot) zaman alanı göstergeleri bakımından diğer yaklaşımlardan daha iyi performans sergilediği gözlenmiştir.
|
Accurate estimation of fuel cost curve parameters in thermal power plants is of great importance because these parameters directlyinfluence the economic dispatch calculations. In this paper, a semidefinite programming (SDP) approach was proposed for theestimation of fuel cost functions' parameters in thermal power plants. The parameter estimation problem was designed as aminimization problem, where the objective function was accepted as the total absolute error (TAE) in the study. Also, linear,quadratic, and cubic fuel cost functions were used to estimate the fuel cost parameters. Different fuel types such as coal, oil andgas were preferred for simulation studies. The results achieved from the semidefinite programming method were compared withthat of particle swarm optimization (PSO), artificial bee colony (ABC), crow search algorithm (CSA) and least error square (LES)methods, respectively. The performance of the methods were compared according to the TAE parameter. Simulation results showedthat SDP method is more successful than other methods considered in this paper. Clearly, the present paper showed that SDP hasa higher potential to solve parameter estimation problems.
|
In a search process, getting trapped in a local minimum or jumping the global minimum problems are also one of the biggestproblems of meta-heuristic algorithms as in artificial intelligence methods. In this paper, causes of these problems are investigatedand novel solution methods are developed. For this purpose, a novel framework has been developed to test and analyze the metaheuristic algorithms. Additionally, analysis and test studies have been carried out for Symbiotic Organisms Search (SOS)Algorithm. The aim of the study is to measure the mimicking a natural ecosystem success of symbiotic operators. Thus, problemsin the search process have been discovered and operators' design mistakes have been revealed as a case study of the developedtesting and analyzing method. Moreover, ways of realizing a precise neighborhood search (intensification) and getting rid of thelocal minimum (increasing diversification) have been explored. Important information that enhances the performance of operatorsin the search process has been achieved through experimental studies. Additionally, it is expected that the new experimental testmethods developed and presented in this paper contributes to meta-heuristic algorithms studies for designing and testing.
|
Gravitational Search Algorithm (GSA) is based on the acceleration trend feature of objects with a mass towardseach other and includes many interdependent parameters. The gravitational constant among these parametersinfluences the speeds and positions of the agents, meaning that the search capability depends on the largescalegravitational constant. The proposed new algorithm, which was obtained with the use of two operators at differenttimes of the call and sequentially doing works, was named as Sequentially Modified Gravitational SearchAlgorithm(SMGSA). SMGSA is applied to 10 basic and 6 composite benchmark functions. Each function is run30 times and the best, mean and median values are obtained. The achieved results are compared with the GeneticAlgorithm (GA), Particle Swarm Optimization (PSO) and GSA among the heuristic optimization algorithms.Between GSA and the operator for each function convergence speed, standard deviation and graphical comparisonsare included. Beside this, by using the Wilcoxon signed rank test, the comparison of the averages of the data astwo dependent groups of GSA and the new operators is performed. It is seen that the obtained results providedbetter results than the other methods. Additionally, in this study, SMGSA was applied to the transformationfunction among image enhancement techniques which are engineering applications. The success of this methodhas been increased by optimizing the parameters of the transformation function used. Effective improvement hasbeen achieved in terms of both visual and information quality.
|
Optimal reaktif güç dağıtım problemi, sürekli ve ayrık kontrol değişkenlerini içerendoğrusal olmayan ve dışbükey olmayan bir optimizasyon problemidir. Buçalışmada, kır kurdu optimizasyon algoritmasının optimal reaktif güç dağıtımproblemine uygulaması sunulmuştur. Kır kurdu optimizasyon algoritması, optimalreaktif güç dağıtım problemi için IEEE-30 ve IEEE-50 baralı sistemlerde testedilmiştir. Benzetim sonuçları, literatürde verilen SHADE-EC algoritmasınınsonuçları ile karşılaştırılmıştır. Karşılaştırma sonuçları, optimal reaktif güç dağıtımproblemini çözmek için kır kurdu optimizasyon algoritmasının üstünlüğünü vedoğruluğunu göstermiştir.
|
