Sensorless control of doubly-fed induction generators based on rotor high frequency signal injection

This paper analyzes the use of high frequency signal injection methods for the sensorless control of doubly-fed induction generators (DFIG). High frequency signal injection methods have been widely investigated for the sensorless control at very low speed and position control of induction machines (IM) and permanent magnet synchronous machines (PMSM). Most of these methods inject a high frequency voltage signal in the stator windings, which interacts with the machine asymmetries (saliencies), modulating the resulting stator high frequency currents, from which the rotor position is estimated. The use of these methods with doubly-fed induction generators (DFIG) is studied in this paper, with special focus on two distinguishing features compared to the case of other types of three-phase machines: 1) it is feasible to inject the high frequency signal in the rotor, since the rotor windings are accessible and 2) as a consequence of this, it is possible to use the method with non-salient machines¹.