Topological method of modular multilevel converter structure based on loop nesting mechanism

Abstract

The invention discloses a topological method of a modular multilevel converter structure based on a loop nesting mechanism, and belongs to the technical field of power transmission and distribution. The topological method comprises the steps of firstly, selecting the number of loop nesting layers and the number of submodules at each layer according to the requirement of the amount of output levels; secondly, setting a capacitance rating and a voltage rating of the submodule at each layer according to the output direct-current bus voltage, the determined number of the loop nesting layers and the number of submodules at each layer; and thirdly, connecting all submodules which are classified at each layer in series, and connecting a communication reactance in series to serve as a conversion bridge arm of a modular multilevel converter, wherein the conversion bridge arm is a novel modular multilevel converter topological structure adopting the loop nesting mechanism. According to the topological method disclosed by the invention, the number of required submodules is obviously decreased under the condition that a certain output voltage level amount and a certain output of the direct-current voltage can be ensured; and moreover, the miscellaneous degree of a primary system is reduced, and the complexity of the system is controlled.

Description

technical field [0001] The invention belongs to the technical field of power transmission and distribution, and in particular relates to a topology method of a modular multilevel converter structure based on a loop nesting mechanism. Background technique [0002] In recent years, high-voltage and high-power fully-controlled power electronic devices (such as IGBTs and IGCTs) have been widely used in long-distance transmission systems and low-voltage distribution networks, and their main application areas are high-voltage direct current transmission based on voltage source converters. (VSC-HVDC) technology. Compared with the traditional two-level and three-level VSC-HVDC, the topology of the modular multilevel converter proposed by Siemens——MMC (submodule is a half-bridge structure) has the advantages of not requiring a large number of IGBTs to be directly connected in series, and the device can withstand voltage Low rate of change, small electromagnetic interference and othe...

AI Technical Summary

Problems solved by technology

Under the same level requirement, the number of required sub-modules is halved, but since the sub-module adopts the H-bridge structure, the amount of switching devices remains unchanged. If the switching devices required for two-level VSC are considered, the amount of devices will increase, so the control The effect of system simplification is not obvious

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