A sensorless PMSM drive using test signals generated by a multilevel converter

In sensorless drives, the reliability of the drive is increased by estimating the rotor position instead of measuring it. At low speed operation and standstill, most sensorless algorithms estimate the rotor position by measuring the response on test signals. This paper discusses a low-speed sensorless algorithm for a permanent-magnet synchronous machine (PMSM) that is supplied by a multilevel converter. Such a converter can be of interest in cases where the machine is supplied with a high dc voltage. Furthermore, by using a multilevel converter, noise can be reduced as smoother current waveforms are obtained and the common-mode stator voltage can be strongly reduced which will reduce the current flowing through the bearings. The aim of this paper is to discuss the generation of test signals by using a multilevel converter.