Improved Position-tracking Accuracy Based on Feedforward-Loop PLL for Sensorless Control of High-Speed PMSM

In sensorless control, position-tracking plays a crucial role and conventional synchronous reference frame phase-locked loop (SRF-PLL) has its disadvantage in that it fails to accurately track the position during motor acceleration and deceleration. Therefore, to improve the dynamic position-tracking accuracy for high-speed permanent magnet synchronous machine (PMSM), a feedforward-loop PLL (FFL-PLL) is introduced as the position-tracking controller in sensorless control. First, a sliding mode observer (SMO)-based sensorless control scheme is introduced. Then, the structures of SRF-PLL and FFL-PLL are presented and steady-state error analysis is performed for both PLLs. Finally, the position-tracking performance of SRF-PLL and FFL-PLL is compared by simulation results. The simulation results validate the effectiveness of the FFL-PLL and prove that it has improved position-tracking capability.