Speed sensorless hybrid field oriented and direct torque control of induction motor drive for wide speed range applications

This paper describes a control scheme of speed sensorless induction motor drive employing salient features of field oriented control (FOC) and direct torque control (DTC) methods. The proposed control system utilizes the advantages of the both FOC and DTC methods and at the same time eliminates their implementation difficulties. The performance of drive in the field weakening region is also studied. A control scheme for robust flux-weakening operation of motor drive is adopted. The basic idea is to adjust the flux reference on the basis of the q-axis stator current error, thus determining a spontaneous flux weakening. Simulation results show that the proposed control scheme is able to follow the reference speed with a reasonable dynamic and relatively low error.