Hybrid-Modulation-Based Full-Speed Sensorless Control for Permanent Magnet Synchronous Motors

This article presents a full-speed sensorless control strategy for permanent magnet synchronous motors (PMSMs) based on a hybrid modulation strategy. The motor operating condition is divided into three ranges: low-speed range, transition range, and high-speed range. A novel two-or-three-vector switching (TTVS) method for rotor position demodulation based on an optimized asymmetric pulsewidth modulation (OAPWM) is proposed in the low-speed and transition regions. A Luenberger position observer based on the conventional symmetric space vector pulsewidth modulation is adopted to demodulate the rotor position in the high-speed region. Additionally, a switching strategy of two modulations and two position estimation observers is proposed to achieve a smooth speed and current transition. Compared with the previous work, the benefits of the TTVS method are to extend the modulation index of the OAPWM and to improve the position estimation accuracy. Finally, the feasibility of the proposed full-speed sensorless control is verified in a 500-W PMSM drive.