Optimized Strategy for Reducing Capacitor Voltage Ripple in Hybrid Modular Multilevel Converter

doi:10.3969/j.issn.1000-7229.2019.04.013

Abstract

Abstract: Modular multilevel converter （MMC） has been widely used in high voltage direct current （HVDC）. The MMC， which consists of half bridge and full bridge submodules， has attracted the attention of domestic and foreign scholars because of the self-cleaning ability of DC short-circuit fault. According to the switching function of the hybrid MMC， the hybrid MMC is modeled under the ideal condition， and the fundamental frequency voltage fluctuation on the capacitor of the submodule is analyzed. A coordination strategy is proposed， which suppresses capacitor voltage fluctuation of sub-module by over modulation. On this basis， a new method for optimizing the number of half-bridge sub-modules based on third harmonic injection is proposed， which reduces the number of new added half-bridge sub-modules and alleviates the side effects of full-bridge capacitance voltage drop caused by simply increasing the modulation ratio. Finally， the correctness and validity of the proposed strategy are verified by simulation of a two-end ±160 kV hybrid MMC in PSCAD/EMTDC.

Key words: hybrid MMC, capacitance voltage fluctuation suppression, over modulation, third harmonic injection optimization

CLC Number:

TM 721.1

LU Feng， LI Yu， XU Jianzhong， ZHAO Chengyong，QU Haitao. Optimized Strategy for Reducing Capacitor Voltage Ripple in Hybrid Modular Multilevel Converter[J]. Electric Power Construction, 2019, 40(4): 110-118.

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