Switching strategy for sensor fault tolerant vector control of doubly fed induction machines

In this paper we propose a multisensor switching strategy for fault tolerant control of rotor wound induction motors operating as stand alone generators. The proposed strategy combines three current sensors and associated observers that estimate the stator flux. The estimates provided by the observers are compared at each sampling time by a switching mechanism, which selects the sensors–observer pair with the smallest error between the estimated flux magnitude and a desired flux reference. The estimates provided by the selected pair are used to implement a vector control law. The switching selection is such that measurements from faulty current sensors are automatically avoided by the switching mechanism, thus maintaining good performance levels even in the presence of a faulty sensor. Simulation results under realistic conditions illustrate the effectiveness of the scheme.