الفهرس 
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Abstract
Wind energy is a prominent facility for supplying utility grid with renewable and clean bulk electricity. Basically, there are many essential reasons for using more wind energy with electricity systems. For instance, wind generation is supported by not only being clean and renewable but also having minimal running cost requirements. However, due to the stochastic nature of the wind and the nonlinearity of the wind turbine system, achieving maximum power extraction of wind energy conversion system has become a significant issue. With the increasing penetration of wind energy into the grid, it is required from wind turbines to stay connected during and after any voltage disturbance or, otherwise, the risk of losing massive amount of power will be raised. Therefore, there is a strong need to enhance fault ride through (FRT) capability for ensuring the full benefit of wind turbines integration with the grid. Variable speed wind turbine topologies contain different generator/converter configurations, based on cost, efficiency, annual energy capturing, and control complexity of the overall system. Permanent magnet synchronous generator (PMSG)- based variable speed wind turbine is considered a promising and feasible technology in wind generation industry. Furthermore, due to its low rotational speed, the gearbox can be avoided. This feature in PMSG-based wind turbine is very important, where the gearbox is one of the most critical turbine components in other wind turbines such as doubly-fed induction generator, since its failure is highly expected. Hence, it requires careful and regular maintenance. In this thesis, comprehensive models of grid connected direct driven PMSG–based wind turbines are presented, via an ac-dc-ac back-to-back converter set. Two control schemes are developed for machine-and grid-side converters. The control scheme of the machine-side converter is developed to apply maximum power point tracking [DOCUMENT TITLE] ABSTRACT II (MPPT) strategy, while the control scheme of the grid-side converter is designed to maintain the dc link voltage at its nominal value. Based on the aforementioned discussion, four techniques are presented in this thesis to achieve MPPT strategy as follow: 1) constant tip speed ratio (CTSR), 2) power signal feedback (PSF), 3) fuzzy logic controller (FLC) and 4) adaptive fuzzy logic controller (AFLC). An extensive simulation results are presented to reveal the robustness and feasibility of these techniques under different wind speed profiles. To guarantee the continuity of operation of PMSG-based wind turbine systems during grid faults, two FRT techniques are proposed are presented as: 1) braking chopper (BC), and 2) supercapacitor energy storage system (SCEES). To evaluate the performance of PMSG-based wind turbine systems with these FRT techniques, comparative simulation results are conducted under different grid faults. The dynamics of the system, comprehensive model of PMSG-based wind turbine and control actions are simulated with detailed model using MATLAB/SIMULINK environment. Regardless of the importance and significance of modeling and simulation processes, experimental studies occupy the most important aspect and remain a big challenge. In thesis, two experimental validations are implemented. The first experiment is based on using 0.3 kW test rig PMSG system with the lab soft environment. The main purpose of studying this test rig is to describe the dynamic performance of PMSG system experimentally. On the other hand, the second experiment is based on using the dSPACE control board with real-time interface block set libraries equipped with wind speed emulator. The main purpose of this experiment is studying the feasibility and robustness of the MPPT control techniques of PMSG based wind turbines experimentally. This experiment is presented with different wind speed profile using wind speed emulator. In conclusion, this work presents compressive modeling of grid connected direct PMSG-based wind turbines. Various MPPT control techniques are introduced. On the [DOCUMENT TITLE] ABSTRACT III basis of the results, good tracking with high accuracy and lower oscillation rate are obtained after using AFLC. Further, the overall system efficiency is enhanced compared with other MPPT schemes. Moreover, FRT control techniques are introduced. Based on the results, both BC and SCESS are capable of providing satisfactory performance with superior FRT capability for the SCESS compared to the BC. Finally, the experimental studies are presented. Based on the recorded results, good agreement is obtained regarding experimental and simulations results.