Sensorless torque control of AC induction motors

The sensorless version of the nonlinear control method is presented in this paper. Torque control at different operating points are demonstrated. A fast dynamic torque response is presented for different types of loads. These loads are changing linearly or nonlinearly with speed or can be applied as an abrupt step. Nonlinear feedback control of the induction motor is then used to obtain the solutions for these various conditions. A voltage source inverter is used to feed the induction motor. The command values to the PWM algorithm are the stator current and frequency. A slip PI controller is used to develop the stator current frequency. This method makes it possible to avoid the calculation of the rotor angular speed. Thus, this paper introduces a significant innovation in the electrical drive system based on the nonlinear control theory of induction motors. Comprehensive simulation results corroborating the developed theory are presented.