Prediction of inductance characteristics of PMSMs in saliency-based sensorless control

This paper proposes an approach to determine the machine parameters in Permanent Magnet Synchronous (PMSM) machines intended for sensorless motion operation. The proposed scheme is based on a Finite Element (FE) perturbation analysis, and provides a methodology to improve accuracy in the calculation of the motor parameters; particularly the incremental inductances. Incremental inductances are essential since play a key role in the performance of sensorless motion. Accurate information about the drive parameters is important, not only when selecting a machine intended for sensorless operation, but for control design and/or commissioning purposes. The presented approach estimates the machine inductances considering not only the effect of the load and saturation, but the influence of anisotropy determined by the rotor position and the current phase angles. Furthermore, cross-coupling which is often ignored in practice is taken under consideration here. The result is a methodology which provides accurate predictions of the system parameters and may provide details about the sensorless performance before actual implementation. The response to the carrier frequency used to extract the saliency components is also evaluated. Details about the type and selection of the carrier frequency are included as a general guide which may be relevant for sensorless design purposes.