Fixed-time observer-based control of DFIG-based wind energy conversion systems for maximum power extraction

•An MPPT controller in combination with state and disturbance observers and fixed-time stability notion is designed for DFIG.•Robustness to the external disturbances and modelling uncertainties is ensured using the proposed SMC method.•An effective solution for eliminating chattering is proposed by using the integral of the sign function in the design of SMC laws.•The fixed-time stability analysis is obtained via the Lyapunov stability theory. This figure illustrates a schematic diagram of the proposed observer-based controller for MPPT applied to the RSC of DFIG based WECS. As this study concentrates on the MPPT objective, only the controller design for the RSC aims to be developed where the wind speed is considered to be below the rated value. The OTSR control is used, so the reference for rotor speed needs to be obtained for defining tracking errors for MPPT. The state and disturbance observers give the estimated data in the controller, and then the controller provides two control voltages to be applied to the RSC. This proposed sensorless controller requires the feedback of rotor speed and reactive power measurements. Also, there is no information about the upper bounds of disturbances in advance. Fig. 4. Overall schematic of the proposed controller for RSC of DFIG. [Display omitted] To extract maximum power from the available wind energy, it is necessary that the doubly-fed induction generator (DFIG) based wind energy conversion system (WECS) outputs that maximum power at each instant of time for different wind speeds. This can be achieved by controlling the rotor voltage of the DFIG. To make it possible, a novel maximum power point tracking (MPPT) controller in combination with state and disturbance observers and fixed-time stability notion is proposed in this paper. The sliding mode control (SMC) method is used to design the observer-based controller and ensure the robustness. The sliding mode state observer is designed while only the measurement of the stator reactive power and rotor speed is required. The modelling uncertainties and external disturbances are estimated by the sliding mode disturbance observer without information about their upper bounds in advance. Then, the combinatorial effect of uncertainties and disturbances are fully compensated by the designed controller. The fixed-time convergence issue is addressed where the bound on the settling time is user-defined using design parameters regardless of initial conditions. The elimination