Variable speed wind turbine systems (VSWT’s) have been in receipt of extensive attention among the various renewable energy systems. The present paper focuses on fuzzy fractional order proportional-integral (FFOPI) control segment for variable speed wind turbine (VSWT) directly driving permanent magnet synchronous generator (PMSG). The main objective of this study is to reach maximum power point tracking (MPPT) through combination of advanced control based on FFOPI control applied to generator side converter (turbine and PMSG). The basic idea of the FFOPI controller is to implement a fuzzy logic controller (FLC) in cascade with Fractional Order Proportional Integral controller (FOPI). A comparative study with FOPI and classical PI control schemes is made. The traditional PI controller cannot deliver a sufficiently great performance for the VSWT. However, the results found that the proposed approach (FFOPI) is more effective and feasible for controlling the permanent magnet synchronous generator to mantain maximum power extraction. The validation of results has been performed through simulation using Matlab/Simulink®.

A robust controller for an AC induction motor is designed using principal gains method to govern stator currents. State space equations of an AC induction motor in α-β stator fixed frame are nonlinear with respect to rotor speed. Nonlinear equations are rewritten to parameter from describing dependency on rotor speed which is assumed to be known by measurement or by estimation. A nominal model (ω=0rd/s) is considered for synthesis, and all regimes dependent of ω are considered perturbed regimes at output multiplicative uncertainty. The singular values of uncertainty are quantified. Robust conditions of stability and performances are given. It is showed, from the results in frequency and time domain, that the principal gains method can be successfully applied to induction motor. 