Sensorless speed control of the induction machine combining field oriented method and DTC

A direct torque control (DTC) scheme for an induction machine is presented. The rotor speed estimation is performed using the oriented field model. Time-frequency spectral methods are used for accurate speed estimation, using the stator current information. Combining these estimation techniques, a precise T_r adaptation is achieved in real time. The proposed method reduces the parameter dependence of the induction machine model in the controller, and removes the need for a speed sensor in the mechanical shaft. The dynamic control performance achieved with this technique is comparable to that obtained using optical encoders