In this paper, a novel rotor speed estimation method using model reference adaptive system (MRAS) is proposed to improve the performance of a sensorless vector control in the very low and zero speed regions. In the classical MRAS method, the rotor flux of the adaptive model is compared with that of the reference model. The rotor speed is estimated from the fluxes difference of the two models using adequate adaptive mechanism. However, the performance of this technique at low speed remains uncertain and the MRAS loses its efficiency, but in the new MRAS method, two differences are used at the same time. The first is between rotor fluxes and the second between electromagnetic torques. The adaptive mechanism used in this new structure contains two parallel loops having Proportional-integral controller and low-pass filter. The first and the second loops are used to adjust the rotor flux and electromagnetic torque. To ensure good performance, a robust vector control using sliding mode control is proposed. The controllers are designed using the Lyapunov approach. Simulation and experimental results show the effectiveness of the proposed speed estimation method at low and zero speed regions, and good robustness with respect to parameter variations, measurement errors, and noise is obtained

A robust vector control intended for a doubly fed induction motor (DFIM) mode is considered. The state-all-flux induction machine model with a flux orientation constraint is replaced by a simpler control model. The double-flux orientation leads to orthogonality between the stator and rotor fluxes, resulting in a linear and decoupled machine control and an optimal developed torque. The inner flux controllers are designed using the Lyapunov linearisation approach. This flux control is exponentially stabilised independently of the speed. Associated with sliding-mode control, this solution shows good robustness with respect to parameter variations, measurement errors and noisse. Finally, a speed controller is designed using two methods: the first with a PI controller and the second with the Lyapunov method associated with a backstepping procedure, especially employed for the unknown load torques. This second solution shows good robustness with respect to inertia variation and guarantees torque and speed tracking. The global asymptotic stability of the overall system is proven theoretically. The simulation and experimental results largely confirm the effectiveness of the proposed DFIM system control.

In this article, a new vector control intended for an induction motor in double fed mode is proposed. It is based on the principle of a double flux orientation of stator and rotor at the same time. Therefore, the orthogonality created between the two oriented fluxes, which must be strictly observed, leads to generate a linear and decoupled control with an optimal torque. The obtained simulation results show the feasibility and the effectiveness of the suggested method, which, in fact, allows to avoid the open loop stability problems inherent to this mode of power supplying of wound rotor induction machine.