An improved rotor position estimator for the control of DFIG based on stator EMF phasor

A new rotor position estimation method based on stator electromotive force (EMF) vector has been presented in this paper. The accurate rotor position is crucial information in the context of decoupled power control of doubly fed induction generator (DFIG) during its standalone as well as grid integrated mode of operation. The proposed rotor position estimation method uses the measured stator and rotor currents and stator voltage to calculate the rotor position based on model reference adaptive system. In this scheme, flux estimation is not required and it is also free from practical integrator prone error during estimation process. The suggested technique is totally insensitive to rotor side parameters, magnetizing inductance variation and corresponding magnetic saturation effect on it. The proposed scheme works well near synchronous speed operation of DFIG and can be started on fly without any a priori knowledge about the initial rotor position. The rotor speed is also estimated without any differentiator and hence the speed computation is robust against signal noises. The proposed method is simple, reasonably accurate and can be easily applied for real time implementation. Proper simulation and experiment on a 3.2kW slip ring induction machine validates the proposed concept.