Robust Nonlinear Sensorless MPPT Control with Unity Power Factor for Grid Connected DFIG Wind Turbines

Abstract

This paper focuses on the sensorless maximum power point tracking (MPPT) and unity power factor operation of a grid connected wind energy conversion system based on the doubly fed induction generator (DFIG). The proposed investigation is based on the nonlinear mathematical models of the wind turbine, the DFIG and the inverters. Based on the synchronized state-space model of DFIG and using stator field oriented vector control, an effective control of stator power is proposed. In this method, rotor speed, stator flux, and rotor resistance are estimated on-line. Field synchronization is provided by a three-phase PLL (Phase-Locked Loop). Unity power factor injection is achieved by controlling the power injected by the rotor and the closed-loop stability is ensured by Lyapunov analysis. Simulation results realized in MATLAB/SIMULINK environment, under different wind speeds, are presented and discussed. These results confirm the validity and effectiveness of the proposed controller.