Sensorless vector control of doubly fed induction machine using a reduced order observer estimating rotor speed and stator variables

This paper presents a new sensorless method for vector control of Doubly Fed Induction Machine (DFIM) where the stator is connected to the grid. The proposed observer in the reduced order estimates the rotational speed and the stator voltages, using only rotor voltages and currents. It has the similar structure with the conventional back-EMF estimator for Permanent Magnet Synchronous Machines. It is designed to estimate the rotor speed and slip between the stator flux and the rotor angle. The proposed algorithm estimates the power factor and the magnitudes of the grid voltage and current. Also, it can detect the failures of the grid voltages. The experimental results of 2kW DFIM are presented to verify the feasibility.