A novel approach to torque estimation in IPM synchronous motor drives

Abstract

Environmental-friendly technologies are growing up fast and they are getting more and more attention. In such a scenario, Interior Permanent Magnet (IPM) synchronous motors have all the peculiarities to satisfy the drive efficiency requests. So far, techniques like the Maximum Torque-per-Ampere (MTPA) were a stimulating field of research, because of the great results in term of energy savings. The MTPA locus brings along additional information that is still worth deepening. A proper rearrangement of the torque expression in MTPA condition, obtained by describing the $q$-axis flux linkage by a polynomial approximation, merged with a simple least-square algorithm, returns a fast and accurate on-line estimation of the electromagnetic torque. The effectiveness of the proposed method is proved by a worked out example, based on a IPM drive model fitted with finite-element analysis and experimental measurements, and including motor saturation effects

Torque Estimation in High-Efficency IPM Synchronous Motor Drives

“…It has been reported here as a challenging issue for more complex control systems, while a different approach, based on the preliminary results described in [17], will be taken as a guideline for the next part of this paper.…”

“…The problem lies in the lower currents region, which is highly sensitive to the control disturbances mentioned above. Actually, the (even small) MTPA errors can influence the whole parameter identification algorithm, [17]. As an effective countermeasure, it is reasonable to keep only the MTPA points at higher current values (i.e., greater than 0.25 p.u.…”