Transient interference analysis and suppression in the secondary circuit of electric control system of kilometer drilling rig

The electric control system of kilometer drilling rig has complex operating conditions, variable loads, and integrates multiple primary circuits. This results in high randomness of transient interference spectrum distribution and easy occurrence of modal aliasing. In order to improve the precision of intelligent perception, the secondary circuit of the electric control system of kilometer drilling rig often uses a high bandwidth gain operational amplifier. The existing models applicable to the secondary port equipment are no longer suitable for the stability analysis of small signal detection circuits. The transient interference frequency domain distribution range of the electric control system of kilometer drilling rig is wide, requiring the circuit to have strong anti-interference capability in a wide frequency range. Traditional anti-interference measures have the disadvantages of narrow frequency bands and poor high-frequency suppression effects. Multi-level RC and LC filtering circuits have problems of impedance mismatch and large volume. In order to solve the above problems, the signal acquisition circuit of the secondary circuit of the electric control system of 15000-kilometer drilling rig is taken as the research object to analyze the transient interference in the secondary circuit. The empirical wavelet transform (EWT) algorithm based on nonparametric scale space is used to divide spectral segmentation points using scale space transformation. The modal components with tightly supported frames are extracted. The kurtosis index characteristics of modal components are introduced to divide transient interference signals and white noise signals. The frequency domain distribution of transient interference is determined. By constructing an equivalent model of the small signal circuit with parasitic parameters in the secondary circuit of the electronic control system, the law between the parasitic capacitance of the feedback circuit pin and the frequency threshold of the interference signal of triggering ringing or self-excited oscillation is explored. The influence of the frequency domain characteristics of the transient interference on the circuit stability is analyzed. The results indicate that when there is a pins parasitic capacitance of 30 pF in the input and output, conducting transient interference signals leads to a decrease in stability. The triggering frequency that causes instability decreases as the pin parasitic capacitance increases. Using the high resistance characteristics of ferrite bead similar to parallel resonance, a second-order filtering circuit is designed. The experimental verification results in laboratry show that when the interference passes through the second-order filtering circuit containing ferrite bead, the interference amplitude is suppressed below −35 dBV in the frequency band above 0.2 MHz sensitive to the signal sampling circuit. The signal sampling circuit has no abnormal output. The interference amplitude of sensitive frequency band in the operation data of the industrial prototype is suppressed below −35 dBV. The actual operation test results are basically consistent with the laboratory test results, meeting the anti-interference requirements.