Design method of self-adaptive Butterworth low-pass digital filter

Abstract

The invention provides a design method of a self-adaptive Butterworth low-pass digital filter. Firstly, coefficients of molecules and denominator polynomials of a discretized Butterworth low-pass filter transfer function are expressed as a function of a product of a sampling step length and a cut-off frequency; then the transfer function denominator is polynomial-converted into a first 1 form to obtain new molecular and denominator polynomial coefficients; a fixed proportional relation between the cut-off frequency of the Butterworth low-pass filter and the fundamental frequency of the detected signal is designed, then a transfer function of the Butterworth low-pass filter is updated according to the fundamental frequency of the detected signal and the sampling step length, and then an input signal is filtered and output by adopting the updated Butterworth low-pass filter. The influence of harmonic waves and high-frequency interference on variable-frequency alternating-current voltageand current signals can be effectively reduced, and the signal detection accuracy is improved; and the gain and the phase shift of the fundamental frequency signal output by the filter are the same when the frequency of the detected signal rapidly changes in a large range.

Description

technical field [0001] The invention belongs to the technical field of anti-aliasing filtering of an aircraft frequency conversion AC power supply system, and specifically relates to a design method of an adaptive Butterworth low-pass digital filter suitable for a frequency conversion AC power supply system. Background technique [0002] Aircraft power supply systems usually contain non-linear loads such as high-power diode rectifier circuits and radars, which cause harmonic pollution to the AC voltage and current of the system. In addition, high-frequency interference such as high-intensity radiation fields will also act on the control circuit, posing a great threat to the stable operation of the system. The anti-aliasing filter is an important means to effectively suppress the adverse effects of harmonic and high-frequency interference on the system. [0003] The three-phase frequency conversion AC power supply system has the characteristics of fast frequency change speed...

AI Technical Summary

Problems solved by technology

[0003] The three-phase frequency conversion AC power supply system has the characteristics of fast frequency change speed (the maximum frequency change rate specified in the national standard is 250Hz / s) and a large frequency change range (the normal frequency range of the wide frequency conversion power supply system currently used is 360Hz-800Hz), etc. Brings great challenges to the design of anti-aliasing filters

On the one hand, this method increases the complexity and cost of the hardware, and at the same time, it is easy to cause discontinuous output when switching between filters with different cut-off frequencies, which affects the performance and stability of the system.

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