Pre-charging and DC fault ride-through of hybrid MMC based HVDC systems

Zeng, Rong and Xu, Lie and Yao, Liangzhong and Morrow, D John (2015) Pre-charging and DC fault ride-through of hybrid MMC based HVDC systems. IEEE Transactions on Power Delivery. ISSN 0885-8977

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    Abstract

    Compared to half-bridge based MMCs, full-bridge based systems have the advantage of blocking dc fault, but at the expense of increased power semiconductors and power losses. In view of the relationships among ac/dc voltages and currents in full-bridge based MMC with the negative voltage state, this paper provides a detailed analysis on the link between capacitor voltage variation and the maximum modulation index. A hybrid MMC, consisting of mixed half-bridge and full-bridge circuits to combine their respective advantages is investigated in terms of its pre-charging process and transient dc fault ride-through capability. Simulation and experiment results demonstrate the feasibility and validity of the proposed strategy for a full-bridge based MMC and the hybrid MMC.