A sensorless vector control of the saturated induction motor using third harmonic voltages

A compensation method of the inductance variations for the speed sensorless control of a saturated induction motor using third harmonic voltages is presented. The air-gap flux of the saturated induction motor contains the space harmonic components rotating synchronous frequency. As a function of the air-gap flux saturation, the dominant third harmonic voltage is used to compensate the nonlinear variations of the mutual inductance depending on the saturation level of the motor. One can measure the amplitude of the space harmonic voltage by using a new method of measurement and compensation scheme. Under the saturated condition, the rotor flux observer for the speed sensorless control is designed using the inductance adaption scheme. The validity of the proposed compensation scheme in the speed sensorless control using rotor flux observer is verified by simulations