Sensorless drive of high-speed bldc motors based on virtual third-harmonic back emf and high-precision compensation

For brushless direct current (BLDC) motor applications, one of the most concerning points in the drive system is the commutation error, which will deteriorate the whole system performance, especially in a high-speed range. Unfortunately, the commutation error is hard to be unitedly eliminated since many non-ideal factors will impact the precision of commutations. To remedy this problem and improve the sensorless drive performance, a novel sensorless control and compensation scheme based on virtual third-harmonic back electromotive force (EMF) combining BEPF-SFE (back EMF power factor combining synchronic-frequency extractor) has been developed. In the proposed method, the virtual third-harmonic back EMF based method is applied to a sensorless drive high-speed magnetically suspended BLDC motor. At the same time, the commutation error is actively compensated by BEPF-SFE-based compensation. An experimental high-speed blower setup is built for evaluating the developed high-speed BLDC motor performance. The effectiveness of the proposed algorithm is validated both through mathematical analysis and experimental results.