MRAS-based speed estimation techniques for vector controlled double inverter-fed slipring induction motor drive

Two different speed estimation techniques for the doubly fed induction machines (DFIM) are reported here. One of the methods is based on reactive power and the other is based on the computation of flux. Model reference adaptive systems (MRAS) are formulated for speed estimation. The uniqueness of the reactive power based MRAS is that the instantaneous reactive power (IRP) is used in the reference model, whereas, steady state reactive power (SRP) is considered for the adjustable model. This type of estimator does not require calculation of the flux and hence reduces computational burden. Also, the scheme is independent of stator and rotor resistance variation. Simulation and experimental results are presented for the validation of the proposed algorithm. The flux based MRAS, independent of stator resistance variation, is also developed for the speed senseless operation of DFIM drive. It is noted that the available flux based MRAS are dependent on the change of stator resistance.