A DFIG Sensorless Rotor-Position Detector Based on a Hysteresis Controller

A simple sensorless method for the detection of the mechanical rotor position of the wound-rotor induction machine in order to implement stator-flux orientation is described and evaluated in this paper. The method is based on the phase comparison of the actual and the estimated rotor currents using the classical model of the machine. It can be conceptually implemented in the rotor or in the stator reference frames. It has some similarity to the model reference adaptive system methodology, but uses a hysteresis comparator instead of a proportional integral (PI) controller. In this way, the method does not need parameter determination for the controllers and shows a considerable independence of parameter uncertainties. Simulation and experimental results show that the method is appropriate for the vector control of the doubly fed induction generator (DFIG) because it leads to the decoupling of active and reactive power chains. It is also appropriate for the control of the DFIG in transients like those when voltage dips occur.