Fault tolerant reconfiguration system for asymmetric multilevel converters using bi-directional power switches

Asymmetric multilevel converters can optimise the number of levels by using H bridges scaled in power of three. The shortcoming of this topology is that the H bridges are not interchangeable and then, under certain faulty conditions, the converter cannot operate. A reconfiguration system based on bi-directional electronic valves has been designed for a 3-phase cascaded H-bridges. Once a fault is detected in any of the IGBTs of any H-bridge, the control is capable to reconfigure the hardware at the faulty phase by means of eliminating the damaged bridge. If the faulty bridge is not the smallest one, then the bi-directional-valve system reconfigure the faulty phase to keep the higher power bridges in operation. In this way, that phase can continue working at the same voltage level by adjusting its gating signals. Some simulations and experiments with a 27-level inverter, to show the operation of the system under a faulty condition, are displayed.