Damping the power-angle oscillations of a permanent-magnet synchronous generator with particular reference to wind turbine applications

The paper describes the use of a novel permanent-magnet synchronous generator for use with a wind turbine. The small pole pitch of the generator allows it to operate at low speeds, be directly coupled to the wind turbine and maintain a direct electrical grid connection. The ability to couple the generator directly to the wind turbine eliminates the need for the usual gearbox, but leads to a generator design where conventional damper windings are ineffective as there is too little space. The paper describes an alternative damping system whereby the stator is allowed limited rotational movement by connecting it to the wind turbine housing via a spring and a mechanical damper. This arrangement allows greater damping of power-angle oscillations than is possible using conventional damper windings. The response of the generator to step changes in driving torque is used to illustrate the effectiveness of such a design. The behaviour of the generator on both synchronisation and during operation in a varying wind is discussed to demonstrate the feasibility of this new design