A DC circuit breaker based on series capacitors and its DC fault handling strategy

Abstract

The invention discloses a DC circuit breaker based on a serial-in capacitor and a DC fault handling strategy thereof. The DC circuit breaker includes a normal through-current branch, a main transfer branch, a cut-off branch, a reactor, and a disconnecting switch. The normal through-current branch is composed of an ultra-fast mechanical switch and a load transfer switch connected in series. The main transfer branch is composed of a main circuit breaker. The cut-off branch is composed of a thyristor valve group and a centralized capacitor connected in series. The load transfer switch is composedof a plurality of sub modules with bidirectional through-current capacity in series-parallel connection. The main circuit breaker can be composed of a plurality of reduced half-bridge sub modules inseries-parallel connection. The nature of a fault current is changed by using a capacitor, and thus, the fault current can be blocked. Moreover, fewer IGBTs are used, and the engineering cost and theoperation loss can be greatly reduced. The DC circuit breaker based on a serial-in capacitor and the DC fault handling strategy thereof have strong reference significance and application value in engineering.

Description

technical field [0001] The invention belongs to the technical field of power electronic systems, and in particular relates to a DC circuit breaker based on a capacitor connected in series and a DC fault processing strategy thereof. Background technique [0002] There are two basic network construction methods for DC power grids: the first network construction method uses a modular multilevel converter (MMC) plus DC circuit breaker scheme based on half-bridge sub-modules. This network construction method is suitable for any number of terminals. The second network construction method uses MMC with DC fault self-clearing capability, such as the MMC based on the full bridge sub-module, but does not require DC circuit breakers. This network construction method is suitable for small-scale networks with less than 10 terminals DC grid. When the half-bridge sub-module MMC plus DC circuit breaker is used to construct the network, the converter station is usually required to continue ...

AI Technical Summary

Problems solved by technology

Although technically feasible high-voltage DC circuit breakers have been developed, they are expensive and bulky, making it difficult to be widely used in power grids like AC circuit breakers

Therefore, DC circuit breakers are still the fundamental technical bottleneck in the development of DC grids

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