A Novel Sensorless Rotor Position Detection Method for High-Speed Surface PM Motors in a Wide Speed Range

In order to improve the performance of surface permanent magnet synchronous motor drives, a novel sensorless drive scheme is proposed in this paper, which is based on the virtual third-harmonic back EMF incorporating a fractional-N phase-locked loop (FN-PLL) and a synchronous frequency-extract filter (SFF). A simple low-pass filter based circuit is used to obtain the commutation points through the virtual third-harmonic back EMF. After that, an FN-PLL is applied to obtain continuous rotor position angles. On this basis, the SFF-based compensation is proposed to compensate the detecting error adaptively. Meanwhile, the field vector control loop for surface PM motor is proposed, which is based on the proposed rotor position detection link and compensation link. An experimental high-speed magnetically suspended blower platform is built. The effectiveness and the feasibility of the proposed method are validated with experimental results.