Sensorless Control of Induction Machines, including Zero Frequency using only Fundamental PWM Excitation

This paper reports the implementation of a sensorless control scheme for AC machines that requires neither a model observer nor a test-signal. The model is based on saliency detection through the use of fundamental PWM excitation and the measurement of the derivatives of the line currents induced by the PWM voltage vectors. Derivation of the rotor position is possible at low and zero speeds without separate test signals and also at higher speed without the knowledge of the machine´s model. Experimental results showing fully sensorless induction motor control at low and higher speeds validate the principle of this method