A new adaptive direct torque control (DTC) scheme based-on SVM for adjustable speed sensorless induction motor drive

This paper describes a combination of direct torque control (DTC) and space vector modulation (SVM) for an adjustable speed sensorless induction motor (IM) drive. The motor drive is supplied by a two-level constant switching frequency SV-based PWM inverter. The inverter reference voltage is obtained based on input-output feedback linearization control, using the IM model in the stator dq-axes reference frame with stator currents and flux as state variables. In addition candidate a Lyapunov function, a novel nonlinear flux observer is introduced which provides simultaneous estimation of the stator flux, rotor speed, rotor and stator resistances. Moreover in the speed loop control of the IM drive, a sliding mode controller is employed that forces the system states to lie on to the sliding surface and makes the speed error exponentially tend to zero. Finally, the effectiveness of the proposed control approach is verified by computer simulation.