A Modular Multilevel Converter with DC Short-Circuit Fault Ride-through

Abstract

The invention relates to a hybrid modular multilevel converter based on a novel clamping sub-module capable of traversing DC short-circuit faults, and belongs to the fields of power electronics technology and power transmission and distribution. The novel clamping sub-module proposed by the present invention can provide back pressure on the path of the DC short-circuit fault current, which helps to rapidly decay the fault current. The converter structure proposed by the present invention is composed of three phases, each phase includes upper and lower bridge arms, and each bridge arm is composed of a number of half-bridge sub-modules, a number of clamping sub-modules and a filter reactor connected in series. The modularized multilevel converter structure that can realize DC short-circuit fault protection proposed by the present invention mixes and cascades the half-bridge sub-module structure and the clamping single-sub-module structure, and can realize the automatic protection of DC short-circuit fault current at a lower cost. It has the advantages of low cost, fast fault current clearing speed, and no voltage equalization problem of internal capacitors in sub-modules.

Description

technical field [0001] The invention relates to a modular multilevel converter capable of traversing DC short-circuit faults, belonging to the fields of power electronics technology and power transmission and distribution. Background technique [0002] Compared with the traditional HVDC transmission technology, the flexible HVDC transmission technology uses full-control switching devices to control the converter, so it has the advantages of flexible control, free compensation of reactive power, and conversion without relying on the AC system. have been extensively researched and applied. Especially the flexible HVDC power transmission system based on the modular multilevel converter structure, many projects at home and abroad have been put into operation or are under construction. [0003] DC short-circuit fault is a serious fault type that must be considered in the design and operation of flexible DC transmission projects. However, for a converter with a half-bridge sub-m...

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Problems solved by technology

For example, the Chinese patent with application number 201310470755.3 and titled "A Modular Multilevel Converter Converter Module Circuit with Short-Circuit Protection" discloses a sub-module structure, which adds a controllable switch inside the sub-module devices and clamping diodes, so that a single sub-module can provide half of its own forward rated voltage back pressure, so that the fault current can be cleared. is charged, so there is a problem of unbalanced capacitor voltage inside the sub-module

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