Sensorless Control of PMSM with Improved Extended State Observer and Feed-Forward Phase-locked Loop

Using a quasi-proportional-resonant controller based on extended state observer (QPR-ESO) and a feed-forward phase-locked loop (PLL), a sensorless control strategy of permanent magnet synchronous motor (PMSM) is proposed to address the issues of back-electromotive force (BEMF) observation distortion by conventional linear extended state observer (LESO) and substantial ramp input error by the PLL. Firstly, by combining QPR and ESO, the motor operating frequency is set to resonant frequency to correctly observe BEMF while decreasing its harmonics. By raising the order of the loop filter (LP) from the perspective of the feed-forward channel, a novel feed-forward PLL is proposed as a method for removing the steady-state position error at ramp input and improving dynamic performance. Finally, the correctness of the theory was established by using MATLAB/Simulink to validate it.