Sensorless speed, position and torque control using AC machine saliencies

This paper describes various methods aimed at tracking the flux and rotor position for cage induction machines without a shaft sensor using specially designed saliencies or natural saliencies. The estimation methods employ a high frequency (HF) signal or test vectors to detect the machine saliency. As is common knowledge, multiple saliences can cause problems to track only one particular saliency. Ways to overcome this problem for rotor position and rotor flux tracking are discussed. The performance of these methods is investigated at all loads at low and zero speed and also at zero fundamental frequency.