Among different kinds of renewable energy resources, wind energy has had the fastest growth in electrical power generation, all around the world. Converting the wind kinetic energy to electrical energy is done by using a wind turbine connected to an electrical generator. One of the generators which is used for this purpose is doubly fed induction generator.In this machine, torque and electrical power of the machine’s stator can be controlled by feeding the rotor windings with proper voltages. everal methods have been proposed for controlling this machine’s power components directly which are justify; TEXT-INDENT: 18pt; MARGIN: 0cm 0cm 0pt; unicode-bidi: embed; DIRECTION: ltr" In above method of power control, poorly damped oscillations are seen in stator’s active and reactive power and electromagnetic torque of the machine. In this thesis the linear model of the whole control system is obtaind in grid flux referenc frame, assuming that the amplitude and frequency of the stator voltages are constant. By using this model it is shown that the cited oscillations refer to the poorly damped poles of the contol system which have an important role in forming stator flux of the DFIM. Afterwards, it is shown that these poles’ damping cannot be improved by changing integral and proportional gains of PI controllers which are used in this method. Because of the control system high order, this analysis is done numerically and in the specific range of ±100% of normal integral and proportional gain values. Then, according to the transition matrix of the contol system the entries of the transition matrix that affect the real part of these poorly damped poles are recognized and two methods are proposed for improvement of these poles damping. Finally Simulation results are presented in both improved and not improved systems in order to verify the proposed methods. Comparison of stator flux, active power, reactive power and electromagnetic torque figures in improved and not improved direct decoupled contol systems shows the effectiveness of the proposed methods. Keywords: Renewable Energy Resources, Doubly Fed Induction Machine (DFIM), Direct Power Control (DPC), Direct Decoupled Power Control (DDPC), Transition Matrix, PI Controller.
