Flexible DC line fault detection method and device

Abstract

The invention discloses a flexible DC line fault detection method and device. The method comprises the following steps: obtaining an average capacitor voltage of sub-modules of upper and lower bridgearms of any phase of converter stations on both sides of a flexible DC line; and judging the type of a DC line fault according to the relationship between the average capacitor voltage of the sub-modules of the upper and lower bridge arms and a rated capacitor voltage. By adoption of the technical scheme disclosed by the invention, whether the DC line has a unipolar grounding fault or an interpolefault can be judged through the information of the internal capacitor voltages of the converter stations. In the scheme, the fault loop is analyzed, the principle is relatively simple, the detectionresult is reliable, the implementation process requires less equipment, and meanwhile the requirements for the equipment sampling rate are lower.

Description

technical field [0001] The present application relates to the technical field of power systems, and in particular to a method and device for detecting a fault in a flexible DC line. Background technique [0002] In the flexible DC transmission project that has been put into operation, the protection of DC transmission lines still uses the relay protection principle of traditional DC transmission lines, and the line protection performance is difficult to meet the requirements. On the one hand, when the flexible DC line is faulty, because the DC capacitor is directly discharged through the faulty line, the fault current has a fast climbing speed and a large amplitude holding point, which will cause damage to the system or components in a short time; on the other hand, due to The DC circuit breaker technology is immature, and the DC side fault cannot be disconnected by the DC circuit breaker. In order to eliminate the DC voltage unbalanced distortion caused by the line fault, a...

AI Technical Summary

Problems solved by technology

[0003] At present, MMC-HVDC (Modular Multilevel Converter Type Direct Current Transmission) system research is mostly used in fault control management and fault characteristics, but there are few detection methods for DC line faults, which are suitable for traditional DC transmission faults Detection methods such as boundary detection and traveling wave method are not suitable for MMC-HVDC system, the main reason is that the output waveform of MMC converter is of high quality and lacks boundary conditions such as DC filter and smoothing reactor; although traveling wave protection operates quickly , but it requires a high sampling rate for the device, and is susceptible to disturbances such as noise and lightning strikes

Images