DC grid fault handling strategy based on in-situ detection and in -situ protection

Abstract

The invention discloses a DC grid fault handling strategy based on in-situ detection and in -situ protection. The strategy is applied to a flexible DC grid which is based on a half-bridge sub-module MMC (Modular Multilevel Converter), is connected by overhead lines and is equipped with hybrid high-voltage DC circuit breakers. When a line in the DC grid has a DC fault, the circuit breakers at the two sides of the line complete fault detection and tripping action independently according to the magnitude of current flowing through a load transfer switch. There is no need for coordination between the two circuit breakers, and there is no need for a relay protection system to locate the fault. The fault handling strategy is of very high rapidity and selectivity, and fault handling can be generally completed in a few milliseconds. The fault handling strategy is very suitable for a DC grid. The level of fault current needing to be cut off by the DC current breakers can be lowered greatly. Therefore, the cost of DC circuit breakers is reduced, and the application prospect of the flexible DC grid is improved.

Description

technical field [0001] The invention belongs to the technical field of power systems, and in particular relates to a DC power grid fault processing strategy based on local detection and local protection. Background technique [0002] With the depletion of fossil energy and the increasing pressure to improve the environment, it is imperative to develop and utilize new energy on a large scale. In order to solve the problem of new energy grid connection and consumption, flexible DC grid technology based on voltage source converters, especially modular multilevel converters (MMCs), is gradually becoming a hot spot in academic research. The flexible DC power grid can make full use of the complementary characteristics of various energy resources and the existing AC and DC power transmission and distribution equipment to realize the optimal allocation of energy resources in a wide area and a large range, the reliable access of large-scale new energy power, and the existing power sy...

AI Technical Summary

Problems solved by technology

If the fault location speed of the DC grid stays at the fault location speed of point-to-point traditional DC transmission, that is, the fault location time is about 10ms, then the fault current level required to be cut off by the DC circuit breaker will rise to a very high level, making the DC circuit breaker The cost of construction has risen sharply

The consequence is that the application of the half-bridge sub-module MMC plus DC circuit breaker is severely limited.

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