Sensorless techniques have shown significant advantages in terms of system reliability enhancement and system cost reduction, hence those attract much popularity in motor drives. Among various sensorless techniques, the schemes based on phase-locked loop (PLL) are generally used. The estimated position of the conventional PLL may suffer obvious observer errors when tracking the ramp frequency and it needs time-consuming parameter tuning. To address these, in this paper, a new scheme based on the active flux which employs the concept of model predictive control is proposed for sensorless control of permanent magnet synchronous motor (PMSM) drives. A brief introduction of the active flux observer based on the hybrid model is first given. The estimated active flux is used as the inputs of the PLL. Following that, the properties of the finite-position-set-phase-locked loop (FCS-PLL) scheme are detailed. Considering the disturbance of noise and measurement error, the proposed FCS-PLL scheme may suffer from performance degradation. An amplitude normalization (AN) unit and the tracking differentiator (TD) are introduced in the estimation scheme to ensure estimation performance. The assessment of the proposed FCS-PLL scheme has been verified by simulations.

sensorless control; PMSM drives; active flux; FCS-PLL