Fault tolerant operation of power converter with cascaded cells

Multilevel converters based on cascaded cells are well suited for high power applications, due to good control performance, extensive modularity and excellent harmonic distortion. A vital requirement in high power converters is being fault-tolerant, so that a single fault in a cell does not lead to the trip of the entire converter. This paper presents a strategy for fault-tolerance on cell level with Integrated Gate Commutated Thyristors (IGCT). The concept is based on initiating a surge in a phase leg in a failing cell, limited by a di/dt reactor leading to a short circuit failure mode of the IGCT thereby excluding the cell from the chain.