Sensorless scalar and vector control of a subsea PMSM

Abstract

This thesis deals with the position-sensorless control of a subsea PMSM, which is fed by a remote VSD. Two V=f control alternatives are implemented for the startup of the PMSM and a sensorless vector controller is designed for operation at higher speeds. Several simulations are performed, in order to investigate the performance of the implemented models and to determine the optimal control settings. The conclusions drawn from the simulation results are validated with measurements on a lab model. The obtained results demonstrate that the implemented V=f control schemes can provide secure startup for the PMSM. The smoothness of the startup depends on the initial rotor position and on the load of the motor. One of the two V=f controllers accelerates the PMSM with significantly lower current, thanks to its ability to produce a more precise voltage reference. During vector-controlled operation, maximum efficiency can be achieved and the response of the system to load disturbances is almost ideal. Furthermore, the implemented fieldweakening algorithm can extend the speed range of the PMSM by up to 17:6% for the considered load.