Zero DC voltage fault ride-through control method of multilevel modular converter (MMC) under asymmetric state of bridge arm parameters

Abstract

The invention discloses a zero DC voltage fault ride-through control method of a multilevel modular converter (MMC) under an asymmetric state of bridge arm parameters. Sub-modules in the MMC all employ full-bridge sub-modules, an auxiliary loop is added among bridge arms of the same DC bus side to build a new topology, energy equalization of three upper bridge arms and energy equalization of three lower bridge arms are maintained when the auxiliary circuit among the bridge arm works during the zero DC voltage fault ride-through process, all modular voltages are integratedly equalized by adjusting voltage deviation among the upper bridge arms and the lower bridge arms, a fault current is enabled to be eliminated during the zero DC voltage fault ride-through process of the MMC, reactive power support is continued to be provided for an AC system, and the energy equalization of the sub-modules is maintained particularly when the bridge arm parameters of the MMC are asymmetric. By the topology and the control method thereof, the voltage deviation caused by asymmetric bridge arm parameters can be jointly borne by the six bridge arms, the integral energy equalization is maintained, a short-circuit current is limited to a low level, and zero DC voltage fault ride-through is achieved.

Description

technical field [0001] The invention belongs to the technical field of flexible direct current transmission, and in particular relates to an MMC zero direct current voltage fault ride-through control method under a state of bridge arm parameter asymmetry. Background technique [0002] Flexible DC transmission technology (voltage sourced converter based high voltage direct current, VSC-HVDC) is one of the key technologies for building Energy Internet and DC distribution network. Modular multilevel converter (MMC) relies on the static The advantages of voltage equalization, high efficiency, and low electromagnetic interference have become the main topology of the flexible HVDC converter station. During the development of VSC-HVDC technology, DC short-circuit fault ride-through is one of the important issues currently facing. Although the half-bridge sub-module used in the traditional MMC topology has the advantages of low cost and high efficiency, it does not have DC fault rid...

AI Technical Summary

Problems solved by technology

[0004] Aiming at the problem that when the full-bridge MMC bridge arm parameters are asymmetrical, it is difficult to equalize the voltage of the upper and lower bridge arm sub-modules during the zero DC voltage fault ride-through process, and the output voltage of the DC side is not zero, the present invention proposes a bridge arm parameter asymmetry The MMC zero-DC voltage fault ride-through control method in the state ensures that the MMC clears the fault current during the zero-DC voltage fault ride-through process, continues to provide reactive power support to the AC system, and maintains the energy balance of the sub-modules

Images