High Frequency Square Wave Injection Method Based on Cascaded Pure Delay Filter

The high-frequency square wave injection method is one of the most widely used sensorless control strategies in the low-speed field of permanent magnet synchronous motor (PMSM). However, in the signal extraction process, it is usually necessary to introduce a band-pass filter, which is sensitive to the frequency change and can easily cause significant delay and distortion to the signal. Aiming at this problem, this paper proposes a signal extraction method based on cascaded pure delay filter. Subtract the sampled current from the sampled current delayed for a certain period of time to achieve filtering effect. Finally, the method was validated through simulation to have good signal extraction performance.