Voltage-sharing control method for optimizing average switching frequency of MMC (Modular Multilevel Converter)

Abstract

The invention discloses a voltage-sharing control method for optimizing the average switching frequency of an MMC (Modular Multilevel Converter), and the method comprises the steps: taking a submodule alternate number optimization method as a core, carrying out the reordering of a marked input group and an input group to form a reordering group, selecting a submodule from the reordering group, setting the selected submodule to be cut off, and setting the sub-modules which are not selected and are set to be cut off in the input group to be input, so that the situation that the voltage of the individual sub-modules of the input group is higher than or lower than the voltage of the individual sub-modules of the cut-off group is effectively avoided, alternative switching of the unnecessary sub-modules is eliminated, the voltage balance effect can be guaranteed, and the switching frequency of the MMC system can be reduced. On the basis of a sub-module alternate number optimization method, whether a sub-module alternate number optimization program needs to be started or not under the actual operation working condition is determined by adding preposition judgment, and the switching frequency can be further reduced.

Description

technical field [0001] The invention belongs to the technical field of electric power transmission and distribution, and in particular relates to a voltage equalization control method for optimizing the average switching frequency of MMC. Background technique [0002] Modular multilevel converter (MMC) is different from two-level and three-level converters. It adopts the cascading method of multiple sub-modules, which has high scalability, high output waveform quality, and low loss. It has gradually become a research hotspot in the field of HVDC transmission. With the continuous improvement of capacity and voltage level, the number of sub-modules and power semiconductor devices in the high-voltage and large-capacity MMC system is also increasing rapidly, which leads to the increasingly prominent problem of converter valve operating loss. [0003] At present, the MMC-HVDC systems that have been put into operation at home and abroad widely adopt the nearest level modulation (...

AI Technical Summary

Problems solved by technology

[0005] Aiming at the deficiencies of the above-mentioned technologies, the present invention provides a voltage equalization control method that optimizes the average switching frequency of the MMC, which solves the problem that the existing technology cannot dynamically adjust the fixed rotation number according to the switching status of the sub-modules in the bridge arm under different circumstances, resulting in unreasonable Technical issues of necessary sub-module rotation switching

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