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 frequency 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, although the applicability to surface-mounted permanent magnet synchronous machines is also briefly discussed. Experimental evaluation of saturation effects in two induction machines is included, as well as simulation results demonstrating sustained torque control at zero fundamental frequency.