New control scheme for doubly-fed induction generators to improve transient stability

In this paper the model and control scheme of a Doubly-Fed Induction Generator (DFIG) is presented. The controllers are designed in order to take into account the different operating conditions of the generator. In normal operations the DFIG can work with variable rotor angular speed between a minimum and a maximum value, covering a wide range from subsynchronous to supersynchronous angular speeds. Up to the rated value, the rotor angular speed is regulated to those values which allow transferring the maximum wind power into electrical power. For angular speeds higher than the rated one, a blade pitch angle regulation limits the transferred power to prevent damages to the machine and instability. A single DFIG connected to a high voltage network has been implemented with ATP-EMTP [12]. Simulations are obtained considering normal operating and fault conditions. Related to this last case, a new stabilizing technique is proposed to improve transient stability.