Sensorless Drive for High-Speed Brushless DC Motor Based on the Virtual Neutral Voltage

The brushless dc (BLDC) motor can be driven by either pulse-width modulation (PWM) or pulse-amplitude modulation (PAM) techniques. Unfortunately, neither of them can be the most suitable method for the high-speed BLDC motor in the wide speed range, so a hybrid drive method combining PWM and PAM is first introduced. Then, this paper proposes a new sensorless control method based on the virtual neutral voltage for high-speed BLDC motor to suit for this hybrid drive method. In order to obtain the commutation signals from this seriously unclear voltage signal due to the commutation notches and electromagnetic interference, a low-pass filter with super low cutoff frequency is employed at the price of a large phase delay. Meanwhile, a novel sensorless control method based on the transition between “90-α” and “150-α” is introduced to handle the severe phase delay. At last, the feasibility and effectiveness of the proposed drive method and the sensorless control method are verified by several experiment results.