The design of IGCT Gate-Unit equipped in the three-level NPC converter

Due to the “Hard Drive” technique implemented by the integrated Gate-Unit, “Integrated Gate-Commutated thyristor” (IGCT) has lots of outstanding features and becomes the best choices of medium voltage applications. In three level NPC IGCT converter, because of the complex commutation transient process, the IGCT works in different conditions such as anti-parallel diode forward recovery, reverse recovery, current commutated from anti-parallel diode to GCT and so on, the Gate-Unit must judge the conditions and do the correct responses such as status feedback, decrease the back-porch current and inner retrigger. In this paper, the characteristics of the GCT works in three-level NPC converters are detailed analyzed. A Gate-Unit to drive 4000A/4500V asymmetric GCT is designed and tested in a three-level NPC PEBB, and the experiment results verify the good performance of the designed Gate-Unit.