Transducerless field orientation concepts employing saturation-induced saliencies in induction machines

This paper explores the tracking of high-frequency magnetic saliencies created by saturation as a means of continuously estimating the position and magnitude of flux for transducerless field oriented control at zero and low speed operation. Tracking is based upon inverter-generated high-frequency signal injection with demodulation incorporating heterodyning and a closed-loop tracking filter. Integration of the tracking scheme with the voltage model in a closed-loop flux observer topology is proposed as an attractive means of achieving very wide speed range transducerless field oriented control. The focus is toward induction machines, the applicability to surface-mounted permanent magnet synchronous machines is also briefly discussed. Experimental evaluation of saturation effects in two induction machines is included