Characterization of 4.5 kV–5.5 kA IGCTs within a medium voltage 3L-ANPC phase leg

In 3L-ANPC VSCs the application of additional active switches inverse to the NPC diodes enable additional switching states and commutations. They are used to overcome one important disadvantage of the 3L-NPC VSC - the unequal distribution of semiconductor losses. With an accurate switching model (obtained directly from the measurements) it is possible to improve the junction temperature distribution among the power devices, increasing the output power and/or increasing the frequency and/or decreasing the derating of the converter. This paper presents the characterization of a 4.5 kV-5.5 kA IGCT within a 3L-ANPC phase leg. A quantitative analysis of the switching losses using 5SHY55L4500 IGCTs and D1961SH45T presspack diodes for a current range from 1 kA to 5 kA and junction temperatures between 25°C and 125°C is presented. The 3L-ANPC phase leg performs 32 different commutations. Each commutation exhibit slight differences in the switching losses as a result of asymmetries in the different commutation paths. The switching loss deviation is quantified and finally, a switching loss model is presented.