Abstract: An electric power generator system is provided with improved power efficiency due to a reduced sensitivity to errors in the sensing of angular rotor position. The system includes a power generator with a rotor, and a position encoder connected to sense angular position of the rotor and to generate a position signal accordingly. A processor receives the position signal, calculates an angular position in response, calculates an estimated angular position based on earlier received position signals, and finally generates a processed angular position based on the calculated angular position and the estimated angular position. This processed angular position is a more reliable measure of the rotor position, reducing the influence of short-term errors in the position signal, allowing normal wind turbine operation during temporary position encoder failure, and allowing an orderly shutdown during complete position encoder failure.

Abstract: A variable rotational speed wind turbine includes a doubly-fed induction generator, a rotor current controller for controlling the rotor currents of the generator, a compensation mechanism having a computation mechanism, and an input mechanism for providing input to the compensation mechanism, the input being representative of at least the instantaneous angular speed of the rotor of the generator. The computation mechanism is arranged to compute an instantaneous compensation control output in dependency of the instantaneous angular speed of the rotor of the generator and feed the compensation control output to the rotor, and to compute the compensation control output during operation of the wind turbine to compensate at least partly for dependencies on the rotor angular speed of the locations of poles of a generator transfer function, thus making a resulting generator transfer function substantially independent of variations in the rotor angular speed during operation of the wind turbine.