Sensorless speed control of a small wind turbine using the rectifier voltage ripple

Grid-tied small wind turbines based on permanent magnet generators are usually operated using a basic converter topology based on a passive rectifier, a boost converter, and an H-bridge inverter. The rotor speed signal is rarely obtained from speed or position sensors in this kind of systems. Model-based estimators are rather used for this purpose relying on electrical magnitudes. Despite its complexity all models show inaccuracy under machine parameter change mainly due to temperature. A speed sensorless method is proposed in this paper based on the measurement of the rectifier voltage ripple. This method is insensitive to machine parameter change. The method will bring a significative improvement in the dynamic response of the small wind turbine system under unrated parameter operation. The proposed method is extended to detect the temperature of the electrical generator. Simulations will corroborate the validity of the proposed method.