A fault direction discrimination method and discrimination element for high-voltage AC-DC hybrid power grid

Abstract

The invention proposes a fault direction discrimination method and a discrimination element for a high-voltage AC / DC hybrid power grid. According to the three-phase voltage and three-phase current of the AC bus on the inverter side detected by the acquisition unit, the fault type is judged, and a fault state signal is sent to the fault direction delay judgment module; the fault direction delay judgment module receives the fault direction delay judgment module After the fault state signal is sent out, the fault phase is further judged, and the fault direction is determined through the delayed judgment of the phase angle difference between the current before the fault and the current of the fault component. The invention is beneficial in that it can correctly identify the fault direction under the condition of high-voltage direct current disturbance.

Description

technical field [0001] The invention belongs to the technical field of electric power system transmission, and relates to fault discrimination of high-voltage direct current transmission, in particular to a fault direction discrimination element and a discrimination method for high-voltage AC-DC hybrid power grids. Background technique [0002] At present, high-voltage and ultra-high-voltage AC lines are generally equipped with longitudinal directional protection, and the fault component directional element has perfect performance, can respond to all types of faults, is not affected by load, is not affected by oscillation, and acts quickly, so it is in the longitudinal direction. It is widely used in network protection. According to the principle of superposition, when the AC system fails, the voltage fault component and the current fault component can be obtained. In the actual calculation of the fault direction, the phase between the voltage fault component and the current...

AI Technical Summary

Problems solved by technology

The failure of the AC system at the receiving end causes serious disturbances in the DC system (such as commutation failure), which may cause misoperation of the directional protection

[0005] The traditional directional element based on voltage and current phase angle difference is applied in the scenario of AC-DC hybrid grid. Due to the commutation failure, it will inject negative sequence components into the AC system. At the same time, due to the rapid adjustment of the high-voltage DC system, it will affect the zero The magnitude of the sequence and positive sequence components will cause misjudgment by traditional directional elements

However, the current direction element based on the phase angle difference between the current before the fault and the fault component has been tried in the AC grid, but it has not been applied to the AC-DC hybrid grid under the high-voltage DC connection.

In the traditional AC power grid, the current direction element based on the phase angle difference between the current before the fault and the fault component, because the direction of the power flow is uncertain, the fault direction cannot be determined only by the local information, only the fault polarity can be judged

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