Nearest zero common mode vector modulation method and system for suppressing three-phase mmc common mode voltage

Abstract

The invention discloses a method and system for suppressing three-phase MMC common-mode voltage to the nearest zero common-mode vector modulation, including: (1) calculating the per-unit value of the level number corresponding to the three-phase reference value given by the controller, and obtaining Two levels adjacent to the per unit value of each phase; (2) According to the two adjacent levels obtained by each phase in (1), a total of 8 vectors can be synthesized for the three phases, from which 3 common-mode voltages are selected as (3) Compare the zero common-mode vector obtained in (2) with the reference vector given by the controller, and the vector with the smallest difference is the nearest zero common-mode vector, and use this vector as the control The periodic vector acts on the MMC so that the common-mode voltage can be eliminated. The invention is applicable to MMC with any level / number of sub-modules, can reduce the common-mode voltage output by the converter, thereby suppressing the common-mode current and common-mode interference, and avoiding the complex vector in the traditional space vector method of the multi-level converter The calculation process of positioning and selection.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and more specifically relates to a method and system for near-zero common-mode vector modulation for suppressing three-phase MMC common-mode voltage. Background technique [0002] With the advantages of easy modularization, low switching loss, high withstand voltage, and flexible control, the modular multilevel converter (MMC) has become the most potential alternative for voltage conversion in medium and high voltage applications, and has received extensive research and research at home and abroad. focus on. [0003] In terms of modulation methods, MMC has two types of modulation methods: one is suitable for the situation where the switching frequency is low and the number of sub-modules is large, including modulation methods such as the nearest level approximation, the nearest vector synthesis, and specific harmonic elimination; the other A large category is suitable for situations wh...

AI Technical Summary

Problems solved by technology

[0006] Aiming at the defects of the prior art, the present invention provides a method and system for suppressing the three-phase MMC common-mode voltage near zero common-mode vector modulation, the purpose of which is to reduce the high-frequency common-mode voltage caused by the conventional modulation of MMC to generate common-mode Leakage current and interference, thereby solving the technical problem that the motor bearing of the motor system using MMC for power conversion and the photovoltaic panel of the photovoltaic power generation system are susceptible to damage caused by common mode voltage

Images