Gain Scheduling of Full-Order Flux Observer for Sensorless PMSM Drives Considering Magnetic Spatial Harmonics

This paper analyzes the effect of gain scheduling in the full-order flux observer for sensorless PMSM drives. The analysis shows that the conventional gain scheduling with fixed pole locations is vulnerable to the magnetic spatial harmonics of PMSM, especially at low speeds. To reduce the spatial harmonic disturbance on the angle estimation, a complex-vector style gains scheduling is proposed in this paper. The proposed gain scheduling inherently provides the speed-adaptive pole allocation, and it can effectively filter out the spatial harmonics of PMSM. Besides, a notch filter tuned to the 6th order harmonics, the dominant harmonic component in most PMSMs, is cascaded to the full-order observer. Thanks to the speed adaptive pole allocation and the notch filter, the sensorless observer keeps its stability at 5% of the rated speed under 200% of the rated torque.