Operation analysis of thyristor based front-to-front active-forced-commutated bridge DC transformer in LCC and VSC hybrid HVDC networks

Li, Peng and Adam, Grain P. and Finney, Stephen J. and Holliday, Derrick (2017) Operation analysis of thyristor based front-to-front active-forced-commutated bridge DC transformer in LCC and VSC hybrid HVDC networks. IEEE Journal of Emerging and Selected Topics in Power Electronics, 5 (4). pp. 1657-1669. ISSN 2168-6777

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    Abstract

    The active-forced-commutated (AFC) bridge employs a symmetrical thyristor-bridge with auxiliary self-commutated full-bridge chain-link (FB-CL) circuit to assist its soft transition and forced commutation. This combination can form a thyristor based voltage source converter (VSC) with significantly reduced on-state losses and dc-fault blocking capability. Due to the full topological symmetry of the AFC-bridge, either current direction or dc-link voltage polarity can be reversed for power flow reversal as for the full-bridge modular multilevel converter (FB-MMC). Thus, the AFC-bridge is compatible with both line-commutated-converter (LCC) and VSC terminals in a multi-terminal high voltage direct current (MT-HVDC) network. This paper investigates its front-to-front (F2F) dc-dc application for matching the regional dc grids in a LCC and VSC hybrid HVDC network. Simulation studies are carried out to demonstrate its potentials as a high efficiency multi-functional solution for dc-dc conversion.