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چكيده انگليسي :

An algorithm for electromechanical oscillations damping estimation in power systems Mohammad Mansouri m mansury@ec iut ac ir Date of Submission Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Lnguage Farsi Supervisor Mohsen Mojiri mohsen mojiri@cc iut ac ir Abstract The need for electrical energy with minimal stops causes a wide researches focusing on control mechanisms for improving the stability of power grids Also development of electrical grid various methods of electrical energy production and reaction between powerhouses are motivations to discuss stability analysis in power system especially in the last two decades But stability of electrical grids has faced with serious challenges Electrical networks are prone to different disturbances such as short circuit electromechanical oscillations and subsynchronous resonance These factors could produce sinusoidal signals exponentially damped sinusoidal EDS signals and decaying dc signals that can cause negative effects on power grid s stability These signals are usually undesired and can even cause instability Therefore it is necessary to identify undesired signals and reduced their effects on power system Among different disturbances in power system EDS signals are extremely important because they appear in various fields such as electromechanical oscillations subsynchronous resonance and in dynamic states after fault clearance Therefore it is necessary to offer an efficient algorithm to identify the parameters of EDS signals Due to importance of electromechanical oscillations this study is focused on these disturbances In this thesis an adaptive algorithm is proposed for the estimation of the frequency and damping factor of EDS signals Motivated by second order generalized integrator SOGI structure for frequency estimation of sinusoidal signals a new measurement based method called damped SOGI is proposed for estimating the parameters of electromechanical oscillations Mathematical formulation of proposed algorithm consists of a linear filter and two update law that joint with the filter dynamic provide estimation of the EDS signal parameters Stability properties of the proposed algorithm are investigated based on application of the averaging theory and integral manifold of slow adaptation Various aspects of the proposed algorithm are investigated via simulation Specifically a number of simulations are conducted to show that the proposed method is appropriate for estimation of parameters that have step changes in frequency and damping factor and signals composed of several EDS signals Moreover proposed algorithm is simulated on Kundur s two area system The thesis further contributes in presenting an adaptive algorithm for rejection of the EDS type disturbances affecting a power system using damped SOGI The proposed compensator which is based on the concept of the internal model principle scheme reproduces the disturbance signal in the loop The main advantage of the proposed compensator is that no information of power system dynamics is necessary to design Compared with power system stabilizers and optimal control methods design of proposed method is simpler and less expensive The performance of the compensator is evaluated using simulation on a photovoltaic plant and Kundur s two area system Key Words Electromechanical oscillation exponentially damped sinusoidal frequency damping factor integral manifold averaging theory photovoltaic plants

منصوري، محمد

معرفي يك الگوريتم تخمين ميرايي نوسانات الكترومكانيكي شبكه هاي قدرت

سيگنال سينوسي ميرا , فركانس , ضريب ميرايي , خمينه انتگرال , قضيه معدل گيري , مدلسازي ديناميكي