Six-segment nearest level approximation modulation method to eliminate mmc common mode voltage

Abstract

The invention discloses a six-segment nearest-level approach modulation method for eliminating the common-mode voltage of an MMC (modularmultilevelconverter, modular multilevel converter), which includes: dividing a power frequency cycle into equal parts that meet preset conditions. The first to sixth control areas; within the control area of ​​any phase, obtain the target number of sub-modules input into the upper bridge arm and the lower bridge arm of the other two phases; obtain any phase The target number of sub-modules put into the upper bridge arm, and the target number of sub-modules put into the lower bridge arm of any phase are obtained according to the target number of sub-modules put into the lower bridge arm of the other two phases, so as to suppress the common mode voltage of the MMC. This method can eliminate common-mode voltage, effectively reduce system leakage current and common-mode noise, and effectively solve the problem of high-frequency common-mode voltage in existing MMCs, which can generate leakage current and common-mode interference through stray capacitance, which endangers motor bearings and communications. system technical issues.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a six-segment nearest-level approach modulation method for eliminating common-mode voltage of an MMC (modularmultilevelconverter, modular multilevel converter). Background technique [0002] As a power electronic converter with broad application prospects, MMC has been applied in medium and high voltage fields, and has many advantages: low loss, low step voltage, low electromagnetic interference, etc. Among them, the MMC circuit structure is as follows figure 1 As shown, MMC modulation methods are mainly divided into two types: (1) low switching frequency modulation, such as: nearest level approximation modulation, selective harmonic cancellation modulation; (2) high switching frequency modulation, such as: carrier phase shift modulation , Carrier layered modulation. [0003] However, in the current research on MMC, there is little research on the common-mode voltage....

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Problems solved by technology

[0005] For this reason, the purpose of the present invention is to propose a six-segment type closest level approach modulation method for eliminating MMC common-mode voltage, which can eliminate common-mode voltage, effectively reduce system leakage current and common-mode noise, and effectively solve the problem of existing In MMC, there are technical problems that high-frequency common-mode voltage can generate leakage current and common-mode interference through stray capacitance, and endanger motor bearings and communication systems.

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