Self-adaptive reclosing method for overhead flexible DC power grid

Abstract

The invention discloses a self-adaptive reclosing method for an overhead flexible DC power grid, which belongs to the field of flexible DC power transmission. The method comprises the following steps:when a DC short-circuit fault signal is received, a DC circuit breaker is opened; after deionization, part of sub-modules of a transfer branch of the DC circuit breaker are reclosed; the reclosed sub-modules are discharged through a capacitor, a voltage traveling wave with a preset amplitude is injected into a fault line, and a first singular point of the DC voltage of the line is generated; whenthe voltage traveling wave is reflected at the fault point or at the tail end of the fault line, a second singular point of the DC voltage of the line is generated; singular points of the DC voltageare detected by wavelet transformation; and the fault property of the fault line is judged according to the polarities of the wavelet transform mode extreme values of the first singular point and thesecond singular point, and self-adaptive reclosing is carried out. According to the invention, the problem of secondary impact caused by reclosing of the DC circuit breaker in a permanent fault is avoided, and the requirement of the flexible DC power grid for the switching capacity of the DC circuit breaker is reduced.

Description

technical field [0001] The invention belongs to the field of flexible DC power transmission, and more specifically relates to an adaptive reclosing method for an overhead flexible DC power grid. Background technique [0002] With the increasing demand for grid-connected renewable energy, the multi-terminal flexible DC grid based on modular multilevel converter (MMC) technology has become one of the development trends of the future smart grid. [0003] Considering the power transmission distance, voltage level and cost, flexible DC systems often use overhead lines for large-scale power transmission. Most overhead line faults are transient faults. After the fault is isolated, the system should be restarted quickly to restore the power supply of the system, thereby improving the reliability of the system. At present, automatic reclosing schemes are often used in engineering to restart faults. This method cannot judge the nature of the fault. Once it coincides with a permanen...

AI Technical Summary

Problems solved by technology

[0005] Aiming at the defects of the prior art, the object of the present invention is to provide an adaptive reclosing method for the overhead flexible direct grid, which aims to solve the problem that the existing automatic reclosing causes secondary damage to the overhead flexible direct grid and needs to be opened again, thus Leading to the problem that the DC circuit breaker's breaking capacity is relatively high in the flexible DC power grid

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