Analysis and optimization of hybrid modular multilevel converters under over-modulation conditions

Pengfei Hu*, Zhengxu He, Rui Yin, Jie Guo, Josep M. Guerrero, Remus Teodorescu

*Corresponding author

Research output: Contribution to journalJournal articleResearchpeer-review

2 Citations (Scopus)


This paper firstly analyzes the operating principles of a hybrid modular multilevel converter (MMC) which utilizes a combination of half-bridge submodules and full-bridge submodules, and proposes an improved modulation method. After that, the capacitor voltage fluctuation of sub-module is comprehensively analyzed in over-modulation condition. Furthermore, according to the above analysis, the optimal modulation index resulting in the smallest capacitor voltage ripple is derived based on the proposed mathematical relationship. In order to verify the proposed modulation method, capacitor voltage fluctuation analysis and modulation index optimization, a PSCAD/EMTDC based simulation model is constructed and some experiments are carried out on a scaled-down hybrid MMC prototype. Both simulation and experimental results confirm the correctness of the analysis and optimization.
Original languageEnglish
Article number105578
JournalInternational Journal of Electrical Power and Energy Systems
Publication statusPublished - Mar 2020


  • Hybrid modular multilevel converters
  • Optimization of modulation index
  • Over-modulation
  • Voltage ripple

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