Hybrid Multilevel Converter With Cascaded H-bridge Cells for HVDC Applications: Operating Principle and Scalability

Khaled Hani Ahmed, G. P. Adam , Barry W. Williams, Ibrahim Abdallah Abdelsalam

Research output: Contribution to journalArticlepeer-review

123 Citations (Scopus)


Hybrid multilevel converters are contemplated in an attempt to optimize the performance of voltage source converters in terms of magnitude of semiconductor losses and converter footprint, and to achieve additional features such as dc short circuit proof, which is essential for a high integrity multiterminal HVDC grid. Therefore, this paper considers an emerging hybrid cascaded converter that offers the dc side short circuit proof feature at reduced loss and footprint compared to the existing multilevel and other hybrid converters. Its operating principle, modulation, and capacitor voltage balancing strategies are described in detail. Furthermore, hybrid converter scalability to high voltage applications is investigated. The validity of the modulation and capacitor voltage strategy presented are confirmed using simulation and experimentation. The hybrid cascaded converter is extendable to a large number of cells, making it applicable to high voltage applications, and operation is independent of modulation index and power factor. On these ground, the converter is expected to be applicable for both real and reactive power applications.
Original languageEnglish
Pages (from-to)65-77
Number of pages13
JournalIEEE transactions on power electronics
Issue number1
Early online date28 Jan 2014
Publication statusPublished - Jan 2015


  • DC fault reverse blocking capability
  • half and full-bridge modular multilevel converters
  • hybrid multilevel converters
  • voltage source converter-based high-voltage direct current transmission systems


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