Abstract: The invention relates to a method to control power output of a doubly-fed induction machine to a grid including the steps of measuring grid voltage and grid current in a three phase coordinate system, transforming grid voltage and grid current into a stator frame coordinate system, decomposing the grid voltage and grid current in the stator frame coordinate system in a positive sequence system and in a negative sequence system, calculating active and reactive power in the positive and negative sequence system, and controlling active and reactive power in the positive and negative sequence system.

Abstract: The invention relates to a protection system of a doubly-fed induction machine, the system comprises a doubly-fed induction machine with a stator and a rotor, the stator of said doubly-fed induction machine is connected to a grid and the rotor of said doubly-fed induction machine is connected to the grid via a converter, said converter comprises a machine side converter, a DC-link and a line side converter. The system comprises additionally at least one crowbar, said crowbar is connected to the rotor, at least one DC-chopper provided in the DC-link, a converter controller and a separate protection device. The object of the present invention to provide a protection system and a protection method of a doubly-fed induction machine which can be easily used with high sampling rates and which provides a good protection for the doubly fed induction machine is resolved in that the DC-chopper and the crowbar are controlled with the separate protection device.