A comparison study between the optimal DFIG flux and speed control in presence of magnetic hysteresis and classical control strategies for wind systems

Abstract

In the wind energy systems field, the most common control objective treated by authors is the speed and flux control of the doubly fed induction generator (DFIG). For computing complexity matter, the generator mathematical representation is generally modelled assuming a linear magnetic characteristic. Based on this assumption, the rotor flux control will aim to track a fixed flux reference, mostly its nominal value. The inconvenience with this strategy is that practically, neglecting the nonlinearity of the generator’s magnetic characteristic, optimal performance control cannot be performed. In this study, considering the magnetic flux hysteresis and saturation characteristic, new modelling of the DFIG is presented. Furthermore, a new speed and optimal flux Backstepping controller is designed based on the Lyapunov theory. To prove its performance, a comparison study with different control strategies will be conducted. Simulations considering a wide range of wind speed variations are illustrated in the Matlab/Simulink environment.