Fast estimation and compensation of rotor flux linkage in permanent magnet synchronous machines

Torque controlled permanent magnet synchronous motor (PMSM) drive systems suffer from parameter sensitivity effects especially the variations in rotor flux linkages. In a torque drive, this variation will cause a change in developed torque in the machine. A parameter compensation scheme using reactive power feedback control is proposed in this paper. Reactive power can be calculated in PMSM drives since it reflects change in the rotor flux linkage accurately while not having the detrimental effect of instrumenting the value of stator resistance in the controller. Then this reactive power can be used to compensate for the variation in torque. The proposed scheme is incorporated in the dynamic model of the PMSM drive and verified for step and ramp changes in rotor flux linkage in a torque drive. Simulation results demonstrate the validity of the proposed technique. The contrast between the proposed scheme and another method based on air gap power feedback control is included in this paper.