Sensorless control of induction motor using natural variables with loss minimization

This paper presents an approach to sensorless speed control an efficiency-optimized induction motor using natural and reference frame independent quantities as state variables - the square of the magnitude of rotor flux linkage, active and reactive torques and rotor speed. Utilization of the nonlinear geometric control methodology of input-output linearization with decoupling permits the implementation of the control in the stationary reference frame. This approach eliminates the use of synchronous reference transformation and flux alignment required in classical vector control schemes. The proposed sensorless speed method uses both the rotor voltage equations, which are shown to provide good rotor speed estimation. The efficiency of the induction motor is realized by choosing the optimal: reference rotor flux linkage using an efficiency optimizing formulation. The proposed scheme and their advantages are demonstrated both by computer simulations and some experimental results for motor speed control