Overvoltage Short-Circuit Failures in Three-Level ANPC Converters

Three-level converters, like the Active-Neutral-Point-Clamped type, can experience in certain situations a shorten semiconductor, which leads immediately to an overvoltage problem for another switch with the whole DC-link voltage. As a result, this one also breaks through or otherwise has to be saved by a fast voltage clamping. However, this leads into a high inductive novel short-circuit current path for three semiconductors in series. Depending on the state of a fourth switch, a second low-inductive short can occur, which affects the trends for voltages and currents of the other three switches as well.