Rotor Position Estimation for a Position-Sensorless FOC PMSM Drive—A Super-Twisting-Based Sliding Mode Observer Approach

The fact that the back-EMF voltage on the d-axis is zero can be used to develop a rotor position estimation method for a surface-mounted PMSM (SPMSM). However, d-axis voltage modeling error may degrade the transient-state performance of a position-sensorless drive. Therefore, this paper presents a second-order sliding mode observer (SMO) based position-sensorless Field-Oriented Control (FOC) drive for SPMSMs. In order to alleviate the chattering phenomenon induced by estimated back-EMF as well as phase delay caused by a low-pass filter that are inherent in conventional SMOs, a super-twisting algorithm-based SMO (STA-SMO) with a modified phase-locked loop (PLL) is adopted to precisely estimate the angular position and angular speed of a SPMSM. Moreover, dynamic performance can be further improved due to a well-tracked estimated back-EMF on the d-axis. Finally, the proposed position-sensorless FOC based on STA-SMO is implemented and verified on a 0.75 kW SPMSM using MATLAB/Simulink. Simulation results verify the effectiveness of the proposed rotor position estimation method.