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.