The basic operation principle of the series active power filter for harmonic suppression of frequency converter is analyzed in this paper, and its control method and control circuit are studied.

The work principle of the motor driving airscrew is presented in the dissertation. The reasons and the method of elimination or suppression of torque pulses produced by BLDCM are analyzed.

The paper elaborated on the principle of noise suppression processing by using GHM orthogonal multi wavelets for seismic signal and gave real examples to show the effectiveness of the method.