Real-time multiple IGBT open-circuit fault diagnosis in three-level neutral-point-clamped converters with no additional sensors

Most diagnostic techniques in the literature focus on the occurrence of a single fault, which limits their functionality. This paper presents a real-time diagnostic algorithm for multiple IGBT open-circuit faults in three-level Neutral-Point-Clamped converters. The proposed algorithm is based on an indirect analysis of the converter pole voltage errors and requires no additional sensors, relying only on signals already available to the controller. The algorithm is independent from the load and control strategy and can detect any number of faults. It provides very fast diagnostics, with each fault being diagnosed in as little as 2 sample periods after its first impact in the converter (in favorable conditions). Simulation results are presented for the rectifier case, demonstrating the algorithm´s speed and robustness.