Voltage drift mechanism in modular multilevel converter

Jie Shen, Qin Lei, Stefan Schroder, Marius Mechlinski

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The capacitor voltage drift problem in Modular Multilevel Converter (MMC) system has been widely discussed in the past. It is well known that sometimes the capacitor voltages are balanced, without any active controls. However, due to the uncertainty and lack of theoretical explanations, active capacitor voltage controls are typically preferred for real applications, and the voltage balancing/drift mechanism of MMC topology did not draw much attention in the past. This paper covers this gap: it is explored that the cell voltage drift effect is caused by the sideband overlap effect. Moreover, the requirements of voltage drift effect are discussed systematically. The conclusion is that for high-power applications with limited switching frequencies, low but non-integer carrier ratios are highly preferred to avoid the intrinsic voltage drift between MMC cells. By doing this, active voltage balancing algorithms are only needed as backup.

Original languageEnglish (US)
Title of host publication2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015
PublisherInstitute of Electrical and Electronics Engineers Inc.
Number of pages7
ISBN (Electronic)9781467371506
StatePublished - Oct 27 2015
Externally publishedYes
Event7th Annual IEEE Energy Conversion Congress and Exposition, ECCE 2015 - Montreal, Canada
Duration: Sep 20 2015Sep 24 2015


Other7th Annual IEEE Energy Conversion Congress and Exposition, ECCE 2015


  • carrier ratio
  • modulation
  • sideband overlap effect
  • voltage drift

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering

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