In this paper, we present a robust control of a variable speed Doubly Fed Induction Generator (DFIG)-based Wind Energy Conversion System (WECS), using Fractional Order Control (FOC) to prevent system deterioration under different critical conditions (external disturbance, measurement noise and DFIG parameters variation). In order to extract the maximum power from the wind, a Maximum Power Point Tracking (MPPT) strategy based on rotor speed control is proposed. Furthermore, a vector control strategy is used for controlling active and reactive powers of DFIG. Additionally, a simple design method of Fractional Order Proportional Integral (FOPI) controller is proposed. Finally, the system’s performance is tested and compared according to reference tracking, robustness, disturbance rejection and noise minimization.
Gas turbines are complex processes characterized by the instability and uncertainty of various sources. The range of useful operating in an axial compressor which is part of a turbine gas is limited by aerodynamic instabilities that are surge and rotating stall. This paper presents two intelligent fractional order sliding mode controllers. At first, a robust sliding fractional surface form is proposed to deal with hazardous phenomena which limit compression systems performance, and speed transitions, which can lead to temporary stall development, pressure drop at the output, degrade the effective operation of compressors and consequently gas turbines. Second, to reduce the chattering/fluctuation in control, a fuzzy logic and finite time criterion are used as switching control at the reaching phase in the sliding mode control. Additionally, the controller gains are obtained by offline multi-objective Particle swarm optimization (MOPSO) search. Finally, the surge and rotating stall of a Variable Speed Axial Compressor (VSAC) in a gas turbine are investigated under the system nonlinearities and also in presence of an external disturbance and perturbations. The simulation results signify the performance of the two MOPSO-based fractional sliding mode controllers.
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