Sensorless control of surface permanent magnet synchronous machines using the high frequency resistance

This paper proposes the use of the high frequency rotor resistance for sensorless control of surface permanent magnet synchronous machines (SPMSM) using high frequency signal injection. High frequency signal injection sensorless control techniques normally assume a purely inductive behavior of the machine, the rotor position-dependent differential inductance being the term tracked. A major concern for these methods is the impact that the operating point of the machine and, more specifically, saturation induced saliencies, have on the high frequency inductances and, eventually, on the accuracy of estimated rotor position. Complicated and time consuming signal processing techniques and tedious commissioning procedures are needed in practice to mitigate these problems and to obtain a good performance of the sensorless control. This paper explores the use of the high frequency rotor resistance for sensorless control purposes. A differential rotor resistance is present in SPMSM due to the difference between the electrical conductivity of the permanent magnet material and the rotor lamination. The differential rotor resistance has been found to be significantly more stable with respect to the operating condition of the machine than the differential inductance, allowing simpler implementation and better performance of the sensorless control.