Dynamic Performance Enhancement for Sensorless PMSM Drive Using 3rd-Order-Nonlinear Speed Observer

Recently, nonlinear speed observers, which are used to extract speed or position information from the estimated back electromotive forces (BEMFs) or rotor fluxes, have been introduced for sensorless control of permanent magnet synchronous motor (PMSM). The dynamic performance is improved by nonlinear speed observers, but the mechanical parameters, such as inertia of moment or friction coefficient, should be identified, thus obviously increasing the complexity of sensorless control. In this paper, in order to solve the issue, an effective yet simple 3rd-order nonlinear speed observer (TON-SO) is presented. On one hand, the TON-SO is derived from the nonlinear extended state observer (ESO) without using the mechanical parameters just as conventional quadrature phase-locked loop (QPLL) or speed observer. On the other hand, the proposed TON-SO can resolve the issue that the performance of linear speed observers is relatively deteriorative due to low bandwidth limited by noise and weak disturbance tolerance. To illustrate the superiority, the conventional 2nd-order linear speed observer and 3rd-order linear speed observer are discussed at first, and then the characteristics, stability and coefficient selection of the proposal are analyzed in this article. Experimental results are conducted under varieties of operating conditions to valid the effectiveness and feasibility of the proposal, which achieves better performance compared with conventional 2nd-order speed observer and 3rd-order speed observer.