Estimated Position Error Suppression Using Quasi-Super-Twisting Observer and Enhanced Quadrature Phase-Locked Loop for PMSM Sensorless Drives

To improve the position estimation performance of the permanent magnet synchronous motor (PMSM) drive system, a novel quasi-super-twisting observer (QSTO) combined with the enhanced quadrature phase-locked loop (Q-PLL) is presented in this paper. Different from the discontinuous signum function used in conventional sliding mode observer, the proposed QSTO with continuous nonsmooth terms is employed to estimate the back electromotive force (EMF), which significantly reduces the negative impact of the chattering phenomenon. After acquiring the EMF signal from the QSTO, an effective enhanced Q-PLL is utilized to alleviate the low-order harmonic components generated by inverter nonlinearities and flux spatial harmonics. Comparative experimental results demonstrate the satisfactory performance of the proposed sensorless control strategy.