Method, system and medium for detecting fault of modular multilevel converter sub-module

Abstract

The invention discloses a method, a system and a medium for detecting faults of a modular multilevel converter sub-module. The detection method comprises the following steps of: aiming at a target bridge arm of the modular multilevel converter, sampling a voltage transformer of the target bridge arm at the beginning of a kth control period to obtain a voltage sampling value; obtaining a theoretical calculation value of the sum of output voltages of all submodules of the target bridge arm at the beginning of the kth control period; determining a fault judgment basis lambda according to the difference between the sampling value and the theoretical calculation value of the voltage transformer; and judging whether the absolute value of lambda is less than or equal to a preset threshold value so as to judge whether the target bridge arm has a sub-module fault or not, and the sub-module with the fault can be further positioned. According to the invention, the fault detection of the sub-module can be realized on the basis of not adding other hardwares under the condition that a single bridge arm of the modular multilevel converter is only provided with one voltage transformer.

Description

technical field [0001] The invention relates to the field of power electronic conversion, in particular to a sub-module fault detection method, system and medium of a modular multilevel converter. Background technique [0002] In recent years, Modular Multilevel Converter (MMC) has strong integrity and flexibility, high modularity, good output waveform quality, easy four-quadrant operation, low device switching frequency, and fault handling It has been widely used in the fields of flexible direct current transmission, medium and high voltage power transmission and static var compensation due to its advantages such as strong capacity. The modular multilevel converter obtains a higher voltage level by cascading multiple sub-modules. In practical applications, the number of sub-modules in each bridge arm of the modular multi-level converter is huge. In order to obtain the ideal output Waveforms, balancing sub-module capacitor voltages and bridge arm voltages are required to co...

AI Technical Summary

Problems solved by technology

If a fault occurs, the fault cannot be detected in time and the faulty sub-module is bypassed, which will lead to excessive capacitor voltage of the sub-module, increase of bridge arm circulation, increase of output harmonic content, and even cause damage to other devices, resulting in huge economic losses. loss

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