Modular Multilevel Converters (MMC) can provide significant advantages for power transmission applications, however there are remaining challenges trading off DC fault response, losses and controllability. Alternative multilevel converter topologies using combinations of full bridge and half bridge submodules or series switches allow for competitive efficiency whilst retaining control over the DC fault current. Several possible fault responses are analysed to evaluate appropriate converter control actions. Experimental results from a 60 submodule 15 kW demonstrator are presented to validate the DC fault performance of the full bridge MMC, the mixed stack MMC and the alternate arm converter. It is shown that each can control the current into a low impedance DC fault, and there no requirement to block the semiconductor devices.