Adaptive Fuzzy Vector Control for a Doubly-Fed Induction Motor

This paper presents a new adaptive fuzzy backstepping control (AFBC) scheme for doubly-fed induction machine (DFIM). This proposed controller guarantees speed tracking and reactive power regulation at stator side. The DFIM stator windings are directly connected to the line grid, while the rotor ones are controlled by means of an inverter. Using a state-all-flux model, the stator voltage vector oriented reference frame is adopted. The control design principle is particularly based on the decomposition of the motor model in two coupled subsystems, namely: the stator flux subsystem and the speed-rotor flux subsystem. The stator flux subsystem is stabilized independently of the speed behaviour. The DFIM unity power factor control and speed tracking problem is transferred to the rotor flux control problem. The unknown load torque is estimated on-line by a suitable adaptive law, the nonlinear functions appearing in the tracking errors dynamics and uncertainties are reasonably approximated by adaptive fuzzy systems. The proposed control scheme guarantees the tracking error exponential convergence to a small residual set. The performances of the proposed control system are evaluated in comparison with a non-adaptive backstepping control (NABC) scheme by simulation tests.