Torque and reactive power control of a doubly-fed induction machine by position sensorless scheme

In this paper, a novel control strategy to realize torque and reactive power control of a doubly excited induction machine using a position sensorless scheme is proposed. Compared to the other position sensorless schemes for doubly fed machines, the proposed control method uses only the rotor voltages and currents as the feedback signals, which substantially reduces the costs and enhances reliability of the position sensorless control scheme of the doubly fed AC machine. Independent control of torque and reactive power is also possible, and the doubly fed system can achieve unity or leading power factor, in addition to variable speed operation