Augmented nonsmooth observer for sensorless permanent magnet synchronous motor drives with harmonic suppression

To enhance the performance of the permanent magnet synchronous motor (PMSM) sensorless drive, an augmented nonsmooth observer (ANSO) combined with the modified quadrature phase-locked loop (Q-PLL) is constructed in this article. Different from the extensively utilized sliding mode observer with discontinuous switching terms in sensorless control, the proposed ANSO with continuous nonsmooth terms possesses the ability to eliminate the chattering phenomenon. In addition, the novel ANSO can acquire desirable current measurement noise suppression characteristic by exploiting augmented observer technique. After acquiring the estimated back electromotive force (EMF) signal from the ANSO, a concise and effective adaptive notch filter (ANF) is adopted to improve the conventional Q-PLL to suppress the undesirable speed fluctuation caused by inverter nonlinearities and flux spatial harmonics. Comparative experimental results validate the advantageous behavior of the presented sensorless control scheme.