An optimal control strategy for DFIG

For doubly fed induction machines operating as wind generators (DFIG), the terminal voltage and the active power delivered to the grid are controlled by a PWM converter linked to the machine rotor. The monitoring of the direct and quadrature axis components of the rotor voltage makes possible the control of the terminal voltage and active power, respectively. Currently, this control is performed by proportional-integral (PI) blocks where the gains and time constants are tuned by trial and error method until wanted response be obtained. This work proposes a control strategy based on the system states optimal feedback. This new strategy includes the rotor current control and provides a methodology to computation of the controller parameters. Besides, for the DFIG representation, the electromechanical coupling between turbine shaft and machine rotor is taken into account. Power systems simulations were carried out to evaluate the performance of the proposed control strategy.