Implementation of sensorless control of induction machines using only fundamental PWM waveforms of a two-level converter

This study reports the implementation of a sensorless control scheme for AC machines that requires neither a fundamental 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 fundamental model. Experimental results showing fully sensorless induction motor control at low and higher speeds validate the principle of this method.