Fault-Tolerant Reconfiguration System for Asymmetric Multilevel Converters Using Bidirectional Power Switches

Asymmetric multilevel converters can optimize the number of levels by using H-bridges scaled in the 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 bidirectional electronic valves has been designed for three-phase cascaded H-bridge inverters. Once a fault is detected in any of the insulated gate bipolar transistors of any H-bridge, the control is capable to reconfigure the hardware keeping the higher power bridges in operation. In this way, the faulty 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.