Sub-module topological structure of modular multilevel converter

Abstract

The invention provides an improved structure of a sub-module of a multilevel converter. The structure comprises a first switch module and a second switch interconnected in series, and a negative electrode is connected with a positive electrode of the second switch module. A positive electrode of a first capacitance is connected with a positive electrode of the first switch module, and a negative electrode of the first capacitance is connected with the negative electrode of the second switch module. The negative electrode of the second switch module is connected with the negative electrode of the second switch module, and the third switch module consists of a current-limiting device and a switch device connected in parallel. The switch device consists of an insulated gate bipolar transistor and a diode connected in anti-parallel, and the current-limiting device consists of a capacitance and a diode. The sub-module topological structure is mainly applied to high voltage high-capacity modular multilevel converters, when the side of direct current breaks down, the shut-off of the fault current of direct current is effectively achieved, and breakdown is effectively separated; meanwhile, action of an alternating current breaker is avoided. The sub-module topological structure of the modular multilevel converter is simple in structure and has quick recovery capability from faults.

Description

technical field [0001] The invention relates to the technical field of electric power transmission and distribution, and relates to a novel sub-module topology of a modular multilevel converter. Background technique [0002] Flexible DC transmission technology provides new means and technical solutions for solving the grid-connected bottleneck of renewable energy such as large-scale wind farms, and for the expansion and transformation of urban high-voltage power grids, grid interconnection and island power supply. The strategic choice of the power grid development pattern has been included in the "National Energy Science and Technology "Twelfth Five-Year" Plan" key equipment for high-performance power transmission and transformation, and is a major technical equipment that requires key technological breakthroughs. [0003] Since flexible direct current transmission is developed on the basis of conventional direct current transmission, in addition to the advantages of convent...

AI Technical Summary

Problems solved by technology

In overhead line transmission, the traditional half-bridge structure essentially lacks DC fault isolation capability: when a fault occurs on the DC side, the anti-parallel freewheeling diode of the fully-controlled switching device easily constitutes an energy feed directly connected to the AC system at the fault point The circuit must be cut off by jumping off the AC circuit breaker. The disadvantage is that the mechanical response is slow (2 to 3 cycles are required at the fastest), which affects the normal transmission of power, and may cause overcurrent and overcurrent of the converter valve device. overvoltage

Auxiliary measures such as increasing the rated parameters of the equipment and configuring high-speed bypass switches are often required. Therefore, this topology is not suitable for power transmission on overhead lines that are prone to temporary faults such as flashovers, and it is necessary to lay cables that are expensive and have a low failure rate. line

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