This thesis proposes a fault-detection method about open-switch failures in three phase rectifiers with active switches. The basic configuration of rectifier topology is hybrid active neutral-point-clamped (ANPC) type. The hybrid ANPC circuitry comprises two different kinds of switches, which are silicon carbide-based metal–oxide–semiconductor field-effect transistors (SiC MOSFETs) and silicon insulated-gate bipolar transistors (Si IGBTs). A hybrid ANPC rectifier shows high efficiency converting AC to DC power also with low harmonics in phase currents. The open fault on the switching device is occurred by mainly thermal aging and makes distortion in phase current with degraded power efficiency. In this work, faulty cases and feature of open switch failure are analyzed in stationary reference frame. Open fault in the SiC MOSFETs makes switches cause prompt and serious distortion in the three-phase current, which are possible to detect with conventional method. On the other hand, an IGBT fault does not make any remarkable difference in current or voltage, so the novel detection method is proposed to diagnose the Si IGBT open fault. The proposed method injects a reactive current in an intermittent period to find current distortion by open fault and uses applying intended short switching state. Thus, the proposed method is based on three-phase current measurements and does not use additional hardware to find a faulty switch in a hybrid ANPC. The effectiveness of the proposed detection method is verified through PSIM computer simulations and experimental results.
