An analysis of speed sensorless torque and flux controller for induction motor

A novel speed sensorless torque and flux controller for induction motors is presented and analyzed in the paper. The proposed approach addresses the problem of torque control at both low and high speed, where rapid speed changes can occur. The idea is realized using a nonlinear flux observer by introducing a nonlinear stator frequency dependent gain in the rotor flux observer, thus enabling operation at low and high speeds. Also a stator resistance adaptation algorithm is presented. Thus the observer is robust to the parameter uncertainties. The performance is investigated and verified with simulations and experiments on a 1.5 kW motor drive.