Analysis and Criterion for Inherent Balance Capability in Modular Multilevel DC–AC–DC Converters

X. Xiang, Y. Qiao, Y. Gu, X. Zhang, T. C. Green

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Modular multilevel dc-ac-dc converters (MMDAC) have emerged recently for high step-ratio connections in medium-voltage distribution systems. Extended phase-shift modulation has been proposed and was found to create the opportunity for inherent balance of submodule capacitor voltages. This letter presents fundamental analysis leading to clear criterion for the inherent balance capability in MMDAC. A sufficient and necessary condition, with associated assumptions, to guarantee this capability is established. Using the mathematics of circulant matrices, this condition is simplified to a coprime criterion which gives rise to practical guidance for the design of an MMDAC. Experiments on downscaled prototypes and simulations on full-scale examples both provide verification of the analysis and criterion for the inherent balance capability of MMDAC.

Original languageEnglish
Article number8906076
Pages (from-to)5573-5580
Number of pages8
JournalIEEE Transactions on Power Electronics
Issue number6
Early online date19 Nov 2019
Publication statusPublished - 30 Jun 2020


  • Circulant matrix
  • inherent voltage balance
  • low voltage dc (LVdc)
  • medium voltage dc (MVdc)
  • modular multilevel dc-ac-dc converters (MMDAC)

ASJC Scopus subject areas

  • Electrical and Electronic Engineering

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