Negative-Sequence Second-Order Circulating Current Injection for Hybrid MMC under Over-Modulation Conditions

Pengfei Hu*, Remus Teodorescu, Josep M. Guerrero

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

24 Citations (Scopus)

Abstract

Due to the presence of full-bridge submodules (FBSMs), hybrid modular multilevel converters (HMMCs) consisting of FBSMs and half-bridge submodules (HBSMs) can work under the over-modulation conditions, which means that half of the dc voltage is less than the magnitude of the ac voltage. However, because of the different charging and discharging characteristics of FBSMs and HBSMs under over-modulation conditions, capacitor voltages imbalance may occur if the modulation index exceeds a specific limit. To address this issue, this article first investigates the principles of HMMCs and the energy balance mechanism between the two types of submodules. Based on the theoretical analysis, a negative-sequence second-order circulating current injection method is proposed to keep the capacitor voltage balanced under over-modulation conditions. Finally, the proposed method is validated by both simulation and experimental results.
Original languageEnglish
Article number8681109
JournalIEEE Journal of Emerging and Selected Topics in Power Electronics
Volume8
Issue number3
Pages (from-to)2508-2519
Number of pages12
ISSN2168-6777
DOIs
Publication statusPublished - Sept 2020

Keywords

  • Capacitor voltage balance
  • hybrid modular multilevel converter (HMMC)
  • overmodulation
  • second-order circulating current (SOCC)

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