Fault mitigation of arc-caused short-circuits in a MMC-based multiterminal HVDC system

High-Voltage DC (HVDC) transmission lines offer highly efficient transport of electric energy. If connected to comparatively weak AC grids, self-commutated converters are the proper choice, because they allow to stabilize the grid in case of faults by injecting reactive power. At high voltages of e.g. 400 kV Modular Multilevel Converters (MMC) fulfill all requirements. For testing all relevant aspects of a multiterminal HVDC transmission system, a scaled-down test bench has been built up. The associated real-life system "Ultranet" will use overhead lines. Weather-induced faults (lightning, conductor bouncing und strong wind) are expected and have to be mastered by the converter stations. This paper first introduces the system and the associated test bench and then presents the mitigation of faults caused by arcing.