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 (DFIGs). High-frequency signal injection methods have been widely investigated for the sensorless control at very low speed and position control of induction machines and permanent-magnet synchronous machines. 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 DFIGs is studied in this paper, with special focus on two distinguishing features compared with 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 nonsalient machine