A class of fast dynamics V/f sensorless AC general drives with PM-RSM as a case study

Field oriented (FOC) and direct torque and flux (DTFC) control of AC drives are credited with fast torque response, but, in general purpose sensorless AC drives, the on-line software and hardware control effort and their reliability may seem prohibitive for general applications or, at least for synchronous motors, a starting strategy is necessary. The present paper presents a novel class of V/f sensorless AC general drives with two stabilizing loops-one based on active flux balance and one based on speed error-that provide fast speed dynamics response without steady state error, without speed or current regulators; flux weakening conditions are built in. The exposition of principles is followed by exemplification for IMs, SPMSM, IPMSM, and DC excited SMs and by digital simulations on a PM-RSM (with weak PMs and reasonably high magnetic saliency Ld/Lq>3). Rather promising fast dynamics performance is obtained, in digital simulations for a PM-RSM case study, but more theoretical and then experimental work (which is under way) are needed to fully establish the proposed solutions as practical.