A method for judging the nature of short-circuit faults in flexible DC power grids and a reclosing method

Abstract

The invention discloses a flexible direct-current power grid short-circuit fault property judging method and a reclosing method. The judging method comprises the following steps that: when a short-circuit fault occurs on a direct-current power transmission line in a flexible direct-current power grid, and two direct-current circuit breakers of the line are switched off, the input-side active converter of the line is controlled to generate alternating-current signals, and the alternating-current signals are injected into the line through the commutation branch of the input-end direct-current circuit breaker; and the fault characteristic quantity of the line is detected, the detected fault characteristic quantity is compared with a preset value on the basis that different fault properties are corresponding to different fault characteristic quantities, and therefore, the property of the fault can be judged. According to the flexible direct-current power grid short-circuit fault property judging method and the reclosing method of the invention, after the direct-current short-circuit fault occurs and the direct-current circuit breakers are switched off, the active converter is controlled to generate the alternating-current signals used for identifying the property of the direct-current short-circuit fault; the alternating-current signals are injected into the fault line through thecommutation branch of the direct-current circuit breaker; the property of the fault can be judged on the basis that different responses are generated according to different faults; and therefore, thedirect-current circuit breaker is prevented from reclosing under a permanent fault, and the recovery speed of a power grid of which the instantaneous fault has been removed is accelerated.

Description

technical field

[0001] The invention belongs to the field of flexible direct current transmission, and more specifically relates to a method for judging the nature of a short-circuit fault in a flexible direct current grid and a reclosing method. Background technique

[0002] The flexible direct current transmission system based on the modular multilevel converter (MMC) has the advantages of easy expansion, small line loss, fast and flexible control, etc. be widely used. The DC power grid can flexibly allocate power between various converter stations, and when a converter station exits due to a failure, the remaining systems can still be kept in operation; considering the cost of long-distance and large-capacity transmission, flexible direct transmission The system often uses overhead lines for large-scale power transmission. Therefore, the overhead flexible DC power grid is an inevitable trend in the development of DC transmission technology in the future. Since overhead ...

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