A reduced-order model for speed regulation of induction machines

Designing a control system for an induction motor (IM) is a generally twofold task: (1) controller synthesis and, (2) assessment of its stability. When using the full fifth order dq-frame model, with incomplete state information and unknown disturbances, the controller design and the proof of stability are not trivial tasks. In this paper, we propose a speed controller for the IM using a reduced-order model assuming that the currents and the speed are measured. The unknown flux and the load torque are estimated using asymptotic observers. The closed loop stability of the composite observer-controller system is established using Lyapunov's theory. The new approach provides good performances while reducing the complexity of the analysis and control.