Method and system for earth leakage protection of mine-used variable frequency drive system

Abstract

The invention belongs to the technical field of frequency conversion drives for mines, and discloses a leakage protection method and system for a frequency conversion drive system for mines. The method includes the following steps: S1, four-way synchronous sampling of the three-phase output voltage of the frequency converter and the ground leakage current ; S2, performing common-mode transformation on the measured three-phase voltages to obtain common-mode voltage values; S3, performing Fourier transformation on common-mode voltages and common-mode currents to obtain harmonic voltages and harmonic currents, wherein Fourier The frequency upper limit of the leaf transformation is set as the switching frequency of the frequency converter; S4, all harmonic signals whose voltage amplitude is less than the voltage threshold or the current amplitude is less than the current threshold are discarded; and then among the remaining harmonics, successively calculate the If the phase difference between the harmonic voltage and the harmonic current is within ±10°, it is determined that the resistive circuit is the main component, and the leakage protection signal is output. The invention realizes the function of hierarchical leakage protection and improves the safety and reliability of the variable frequency drive system used in mines.

Description

A leakage protection method and system for a mining variable frequency drive system technical field The invention belongs to the field of mining variable frequency drive systems, and in particular relates to a leakage protection method for mining variable frequency drive systems laws and systems. Background technique [0002] With the popularization and use of the frequency conversion drive system in coal mines, especially on airborne equipment, shearers, continuous miners, shuttles, Most bolters use variable frequency traction system. Due to the traditional leakage protection system, there must be a grounding resistance, which leads to There can only be one set of leakage protection at the back end of the entire transformer. If there are multiple sets, they will inevitably affect each other and cannot work normally. that is At the back end of the transformer, all electrical equipment share a set of leakage protection, and the insulation state of other electrical equi...

AI Technical Summary

Problems solved by technology

[0002] With the promotion and use of frequency conversion drive systems in coal mines, especially on airborne equipment, coal shearers, continuous miners, shuttle cars, and bolters mostly use frequency conversion traction systems. Due to the traditional leakage protection system, there must be a grounding resistance. , resulting in only one set of leakage protection at the back end of the entire transformer. If there are multiple sets, they will inevitably affect each other and cannot work normally.

That is, at the back end of the transformer, all electrical equipment share a set of leakage protection, and the insulation status of other electrical equipment is completely dependent on it, which loses the meaning of hierarchical protection. If the insulation to the ground is low, it is difficult to accurately locate point of failure

For the AC power supply system, the current conventional detection principle in coal mines is zero-sequence voltage current and additional DC method. For standard power frequency electrical equipment, its performance can be fully satisfied, but for variable frequency drive devices, due to the existence of high frequency leakage current, Its zero-sequence voltage and current detection method does not work properly

The additional DC detection method can be barely used, but for the high-power four-quadrant variable frequency drive device, which often malfunctions, it can only be barely used by reducing the sensitivity.

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