Sensorless Control of High-Speed BLDC Motor Based on the Pole-Voltage in the Stationary Reference Frame

This paper proposes a simple sensorless control method of a high-speed BLDC motor for cordless vacuum cleaner controlled using the 2-phase excitation method. In the high-speed region, the sampling number of pole-voltage is limited by the maximum switching frequency. Dual-side (high-side and low-side) PWM approach in the unipolar switching method is adopted to increase the sampling number in the non-excitation region. The detected pole-voltages are converted to the $\alpha \beta$-axis voltage of the stationary reference frame to remove the phase shift delay of phase pole-voltage and to get the continuous angle position. Rotor position can be estimated by the converted $\alpha \beta$-axis voltage, considering the sampling delay of the analog-to-digital conversion and the low-pass filter in the high-speed region. The proposed method is verified by experiments, and the results are compared to that of the conventional sensorless control. The proposed method shows an improved performance in the high-speed region because of the increased sampling numbers of the proposed dual-side PWM method.