الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
As a cost-effective, environmentally friendly, and secure alternative to nuclear and fossil fuel power generation, wind electrical power systems are currently receiving a lot of attention. High-power wind applications frequently employ a unique kind of generators known as doubly fed induction generator (DFIG). Due to its simple controllability, improved efficiency, and increased power quality, it is being employed more and more in wind turbine applications. These applications involve the grid connection and standalone operation as well. Accordingly searching for the most effective control to be used with the DFIG became a challenge for the researchers in this field of study. Majority of the adopted control approaches with the DFIG are formulated based upon utilizing the PWM with linear regulators. All of these facts resulted in making the overall control scheme more complex. Recent studies have shown that the DFIG can be controlled using an advanced control theory which can be adopted without modulators or linear controllers and all of these requirements are fulfilled by the predictive control. This is adaptable enough to incorporate adjustments and extensions of control horizons according to the required applications, the capacity to take into account a multi-objective scenario inside the model, simple system constraints handling, straightforward integration of non-linearities inside the model, and straightforward digital implementation.
Accordingly, the study presented in this thesis is investigating in details the application of predictive control as an advanced approach with its different forms to manage the dynamic performance of a DFIG for standalone operation purpose. The performance is evaluated for the direct driven and wind driven operation as well. All generation system components are initially modeled. Firstly, the detailed mathematical model of the DFIG is introduced in the general rotating frame to give an extra freedom when applying the control. After that, the wind turbine system and its power management unit which adopts the maximum power point tracking (MPPT) principle to optimally exploit the wind energy are modeled and described. Following that, the mathematical model of the isolated load to be fed by the DFIG under standalone operation is described. The load under study is a three-phase induction motor (IM) as an emulating to a realistic loading condition.
To perform a detailed performance comparison, the study applied firstly the traditional vector control; specifically, the stator voltage-oriented control (SVOC) type with both direct and wind driven DFIG. The control design is described in details and the results are extracted. After that, the study formulated different forms of predictive control to be used with the DFIG; some of them recently used and the others are newly designed. The recent used predictive control topologies are the model predictive direct torque control (MPDTC) and model predictive current control (MPCC); meanwhile the new designed predictive scheme is given the title of ‘predictive voltage control (PVC)’. Alternatively, for controlling the operation of the isolated load (IM), the MPDTC principle is used. The design of all predictive controllers is articulated mainly on the type of used cost function as illustrated and described in details within the thesis.
As an additional verification for the performances of all adopted control schemes with the DFIG used in standalone operation case and to assure the superiority of the designed PVC scheme over the other controllers, the dynamics of the DFIG are also evaluated under grid connection state. All test scenarios are carried out using the MATLAB/Simulink software.
Extensive performance evaluation tests are performed, which in conclusion report that the performance of the new designed PVC control exhibits the most effective one compared with the other controllers. Specifically, the designed PVC has a faster response time and simpler structure comparing with the classic SVOC; meanwhile it has faster dynamics, lower torque and flux ripples, lower current harmonics and simpler structure than the MPDTC and MPCC schemes. These facts are confirmed under both standalone and grid connection states while driving the generator shaft through two ways: directly and using wind turbine as we.