A Thermal Management Approach to Fault-Resilient Design of Three-Level IGCT-Based NPC Converters

The three-level (3L) neutral-point-clamped (NPC) converter, introduced by Nabae in 1981, has become the most popular converter topology for high-power medium-voltage industrial drives. Responsible for driving key processes in various industries, high availability of these converters is mandatory, since their maintenance or replacement implies downtimes incompatible with the requirements of the production processes. In this context, this paper discusses a thermal management approach to a fault-resilient design of the 3L integrated gate-commutated thyristor-based NPC converters. The main goal is to reduce the damage extension and restrict the damage pattern within the NPC bridge in case of failures or malfunction of currently employed protection schemes. It is shown that the thermal stress caused by the short-circuit currents can be managed, easing the selectivity and tracing of the damaged components, thus reducing the overall converter downtime and maintenance costs.