Sliding-Mode Observer For Sensorless Control Of Permanent Magnet Sychronous Motor Drives

Abstract

The paper develops a robust sliding-mode based observer to estimate the speed and position in sensorless control of permanent magnet synchronous motor (PMSM) drives using only two phase-current sensors and one dc-link voltage sensor. The nonlinear observer structure contains two main parts. 1) A sliding-mode disturbance observer estimates the electromotive force vector as equivalent control using the PMSM electromagnetic model in stator reference and a speed-adaptive low-pass filter. 2) A phase-locked loop state-observer extracts the speed and position from the equivalent control using a variable-structure PI state-observer. A sensorless PMSM drive with current vector control using this observer is investigated by extensive digital simulation and by experimental tests. The results prove good dynamic performances in medium speed range from zero to rated transient torque, and robustness to real parameter variations.