Sliding Mode Control via Fuzzy Multi-Level Switching control scheme for DFIG based WECS

This paper presents a new sliding mode control (SMC) via fuzzy multi-level switching (FMLS) technique for doubly fed induction generator-based wind energy conversion system (DFIG-based WECS). The main objectives are: 1) extraction of maximum power from the wind by achieving maximal power point tracking (MPPT) strategy, and 2) supplying the grid with zero reactive power. The SMC is combined with FMLS control to minimize the undesirable effect of chattering inherent to the conventional SMC. Based on the measured error, five error levels are selected extra-small, small, middle, large, and extra-large. For each error level there is different switching level. The DFIG and MLS controller will be tested against various perturbations. Simulation results using Simulink/Matlab conclude that the proposed controller succeeded in eliminating perturbation and minimizing the chattering effect. Key-words: Wind energy conversion system, MPPT, DFIG, Sliding mode control, Fuzzy control, Multi-level switching. Nomenclature WT Wind turbine J Turbine total inertia (Kg m) DFIG Doubly fed induction generator f Turbine total external damping (Nm/rad s) MPPT Maximum power point tracking Ω Generator speed (rad/s) d, q Synchronous reference frame index ω, ωs Angular speed, synchronous speed (rad/s) s, r Stator and rotor indices Gb Gearbox coefficient V Wind speed (m/s) v, i Voltage (V), current (A) ρ Air density (kg/mˆ3) φ, Tem Flux (Wb), Electromagnetic torque (Nm) Rb Blades length (m) P,Q Active power (W), reactive power (VAR) Ta Aerodynamic torque (Nm) p Number of poles pairs Pa Aerodynamic power (W) L,M Inductance, mutual inductance (H) Cp Power coefficient R Resistance (Ω) Ωt Wind turbine rotor speed (rad/s) σ Leakage flux coefficient (σ = 1−M/LsLr) 430 S. Labdai et al.