A mmc with zero DC voltage fault ride-through capability and its design method

Abstract

The invention discloses an MMC with zero DC voltage fault ride-through capability and a design method thereof. Integrating the advantages of low cost, high operating efficiency and full-bridge sub-module output negative level of the half-bridge sub-module, adopting the zero DC voltage fault ride-through scheme proposed by the present invention, according to the rated voltage of the half-bridge sub-module and the full-bridge sub-module, and Combined with the rated voltage of the MMC DC side and the peak value of the phase voltage of the AC side, the number of half-bridge and full-bridge sub-modules is calculated; the obtained MMC can effectively reduce the cost of the converter and Improve the operating efficiency of the converter. The technical solution proposed by the present invention is not limited to the combination of the half-bridge sub-module and the full-bridge sub-module, but can also be a half-bridge sub-module and other sub-modules that can output positive, negative and zero levels in the non-blocking state Combinations, such as cross-connect dual half-bridge submodules.

Description

technical field [0001] The invention belongs to the technical field of multi-level power electronic converters, and more specifically relates to an MMC with zero DC voltage fault ride-through capability and a design method thereof. Background technique [0002] At present, with the advantages of no dynamic and static voltage equalization problems and high operating efficiency of switching devices, Modular Multilevel Converter (MMC) has become the first choice for high-voltage high-power converters, especially high-voltage direct current transmission converters. In the field of HVDC power transmission, especially when power transmission is based on overhead lines, MMC-based converter stations often face a relatively high probability of short-circuit faults on the DC side. In the traditional MMC design method, all sub-module topologies are the same. Although the classic MMC (Half Bridge Sub-module MMC, H-MMC) composed of half-bridge sub-modules has the advantages of low cost ...

AI Technical Summary

Problems solved by technology

[0003] In order to improve the overall performance of the MMC, the traditional design method requires the topology of each sub-module to be changed, resulting in an increase in the cost of the MMC and a decrease in operating efficiency

For example, when the power level is the same, the unit cost of F-MMC is about 15% higher than that of H-MMC, and the on-state loss of F-MMC and C-MMC is about 70% and 35% higher than that of H-MMC

In addition, during short-circuit faults on the DC side, especially zero-DC voltage short-circuit faults, although the DC blocking capability can clear the short-circuit faults on the DC side, it cannot inject reactive power into the grid to support the grid voltage

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