Because the turn-on snubber represents supplementary volume, cost and losses to the SM, downsizing it is interesting. Such downsizing is studied in for 2.2kV/1.5kA submodules using press-pack diodes. In these studies the snubber inductor has been reduced to 0.32µH (compared to 3µH), keeping the RCD-clamp of the submodule. A snubber inductor of 320 nH is comparable to the stray inductance encountered in standard IGCT circuits (Lstray in figure 1c). This dramatic simplification of the power circuit would have important consequences on the cost and volume of an MMC submodule. The goal of this study is to determine if the snubber can simply be removed in IGCT-based MMC submodules (or at least downsized even more) if fast enough freewheeling diodes are used.
Arthur Boutry, Cyril Buttay – B.Lefebvre
Presented at EPE’2022 ECCE Europe