Selective Periodic Disturbance Elimination Using Extended Harmonic State Observer for Smooth Speed Control in PMSM Drives

The elimination of periodic torque disturbance in permanent magnet synchronous machine (PMSM) drives is a multifrequency control task, and adding resonant parts to the controller has an impact on the robustness of the system. This article aims to address the torque-ripple reduction in PMSM drives for smooth speed control, where an extended harmonic state observer (EHSO) is designed for estimation and attenuation of the selective periodic disturbance. The defects of applying the conventional bandwidth-parameterization method to the harmonic disturbance observer are explored. To improve the disturbance-rejection capability and the relative stability, a pole-placement strategy is proposed and analyzed through sensitivity function, which can preserve the comparable dynamic performance as the conventional extended state observer at the low-frequency range. The proposed EHSO also features easy parameter tuning and a modular structure for multiple harmonic disturbance rejection. Finally, the proposed method is evaluated on a laboratory PMSM platform.