Thermal Analysis and Balancing for Modular Multilevel Converters in HVDC Applications

Frederik Hahn, Markus Andresen, Giampaolo Buticchi, Marco Liserre

    Research output: Journal PublicationArticlepeer-review

    94 Citations (Scopus)


    The modular multilevel converter (MMC) has become a very attractive solution for interfacing high voltages in hybrid networks. The MMC enables scalability to different power levels, full controllability provided by insulated-gate bipolar transistors, and can achieve very high efficiencies by using a low-switching-frequency method as the nearest level modulation. However, the nearest level modulation requires a capacitor voltage-balancing algorithm, which can result in unbalanced loading for the power semiconductors in the different submodules. Particularly at low-power-factor operation, which could occur in the case of low-voltage ride through and of reactive power injection, the conventional algorithm is no more effective. This paper provides thermal stress analysis of the MMC in operation and proposes a thermal balancing approach, which is embedded in the capacitor voltage-2balancing algorithm. The purpose of the thermal balancing is to achieve similar stress distribution among the different submodules to enhance the lifetime. The junction temperatures in the different submodules are studied for HVDC applications, and this paper proves experimentally that the thermal balance within the submodules is significantly improved.

    Original languageEnglish
    Article number7892875
    Pages (from-to)1985-1996
    Number of pages12
    JournalIEEE Transactions on Power Electronics
    Issue number3
    Publication statusPublished - Mar 2018


    • HVDC transmission
    • Modular multilevel converters
    • reliability
    • thermal management
    • thermal stresses

    ASJC Scopus subject areas

    • Electrical and Electronic Engineering


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