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In this paper we present the control system of a wind turbine based doubly fed induction generator (DFIG) by direct torque control (DTC). The wind energy conversion system (WECS) equipped with wind turbine, DFIG, DC bus and the power convector. The converter is controlled to generate the maximum power from wind turbine generator (WTG) by using maximum power point tracking (MPPT) strategy. The pitch control is also proposed to limit the generator power at its rated value. The DTC is developed to regulate the flux and torque. The simulation results of a 1.5MW doubly fed induction generator show the performances of the control strategy proposed. These results are validated by using the MATLAB/Simulink environment Keywords-Doubly fed induction generator (DFIG); direct torque control (DTC); Maximum power point tracking (MPPT); wind turbine generator (WTG); wind energy conversion system (WECS) I.

Conventional fossil fuels such as coal, oil and natural gas are being reduced and become more and more a source of serious undesirable effects on the environment. Wind power is playing a major role in the effort to augment the share of renewable energy sources in the world energy mix with a continuously increasing penetration into the grid. Wind turbine generators can be divided into two basic categories: fixed speed and variable speed. Variable-speed wind energy systems are presently favored than fixed-speed wind turbines thanks to their higher wind power extraction, improved efficiency, reactive power support and voltage control. This study addresses the problem of control of Wind Energy Conversion System (WECS) in variable speed. To this end, two simultaneous control objectives, namely the maximization of the energy conversion efficiency based on Squirrel Cage Induction Generator (SCIG) wind turbine and the regulation of the active and reactive power feed to the grid, to guarantee Unit Power Factor (UPF), have been established. To deal with the complexity and nonlinearity of the system, the sliding mode control is adopted. Indeed, this technique provides an efficient tool for controller design and presents attractive features such as robustness to parametric uncertainties of the different components of the system. In this way, sliding-mode control laws are developed using Lyapunov stability analysis, to guarantee the reaching and sustaining of sliding mode and stability of the system control. Evaluation of the reliability and performance of the proposed sliding mode control approach has been established on a 3MW three-blade wind turbine. Simulation results demonstrate that the proposed control strategy is effective in terms of MPPT control strategy, active and reactive power tracking trajectories and robustness against system parameter variations.

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In this paper, a nonlinear fractional-order PI (NL-FO-PI) controller is proposed for primary frequency control (PFC) of a wind farm based on the squirrel cage induction generator. The new structure composites a fractional-order operator and nonlinear function to achieve better control performance for the PFC system. The benchmarking process is demonstrated by investigating the performance of fractional-order PI (FO-PI) and nonlinear PI (NL-PI) controllers. Initially, the controller is applied to a single-area power system for design and stability study and then extended to the two-area interconnected wind farm to validate the applicability in the more realistic power system. The proposed control method ensures the balance of power and keeps the system frequency within a suitable range. The simulation results demonstrate that the proposed NL-FO-PI controller provides less percentage overshoot, settling time, rise time, and peak time than other controllers.

This letter investigates real-time implementation of a finite-time control for permanent magnet synchronous motors in the presence of external load disturbance. Firstly, an integral terminal sliding manifold is designed to achieve fast speed, high precision performance, and to enhance the quality of currents by reducing the total harmonic distortion. Indeed, the proposed surface manifold ensures a finite-time convergence of the speed state variable. Secondly, a switching control scheme is added for the system control to force the state systems to converge to their desired values in the presence of load disturbance. Finitetime stability is proved based on Lyapunov theory. Finally, the effectiveness of the designed controller is validated by carrying out real-time experimental studies using eZdspTM F28335 board. According to the experimental results, the proposed controller is easy to implement, improves tracking accuracy, reduces the chattering issues and ensures robustness against external load disturbance.

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