Redundant Position Observer Improvement for Sensorless PMSM at Low Speed

Permanent magnet synchronous machines are commonly used with a switched pulse width modulation inverter in order to obtain an easy to use variable speed actuator. This inverter must feed the machine with a current controlled in magnitude and phase. To achieve this objective the rotor position must be known and can be obtained through an accurate observer algorithm. We focus our attention on a redundant EMF, velocity and position observer, easy to implement and robust to parameters variations. It is well known that this structure does not work well at low speed but taking into account switching and dead time phenomena in the inverter, the observer is improved and global performances are increased especially at low speed