A Modular Multilevel Converter Based on Diagonal Bridge Submodules

Abstract

The invention proposes a modular multilevel converter based on a diagonal bridge sub-module, which belongs to the field of power electronics technology and power transmission and distribution. The structure of the converter is composed of three phases, each phase includes upper and lower bridge arms, and each bridge arm is composed of several diagonal bridge sub-modules and a bridge arm reactor connected in series. The positive terminal of the upper bridge arm is the positive terminal of the DC side of the phase, the negative terminal of the lower bridge arm is the negative terminal of the DC side of the phase, and the connection point between the negative terminal of the upper bridge arm and the positive terminal of the lower bridge arm is the AC side terminal of the phase; The positive terminals of the DC side are connected together to form the positive pole of the DC side of the converter; the negative terminals of the DC side of the three phases are connected together to form the negative pole of the DC side of the converter; the AC side terminals of each phase of the converter are respectively connected to the AC side Each phase line terminal of the grid is connected. The multi-level converter of the present invention can clear the DC short-circuit fault current, and can provide reactive power support for the AC power grid when the DC fault occurs, and the used full-control devices are less and the cost is lower.

Description

technical field [0001] The invention belongs to the field of power electronics technology and power transmission and distribution, and in particular relates to a modular multilevel converter based on a diagonal bridge sub-module. 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] Existing flexible HVDC transmission projects based on modular multilevel converters mostly use DC cables. The probability of DC faults is low, but the cost of the line is high; if ...

AI Technical Summary

Problems solved by technology

Compared with the first type of converter, the second type of converter needs to solve the complex problem of IGBT series voltage sharing, and the DC side filter is larger

The main problem of the first type of converter is that the new sub-modules currently proposed require a large number of IGBTs, and the cost and loss increase more than that of the half-bridge modular multi-level converter.

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