Open-circuit fault diagnosis for single-phase cascaded H-bridge rectifiers in electrical traction systems

The single-phase power electronic traction transformer (PETT) is a power device to realize the higher efficiency and reduction of weight in railway traction system. The single-phase cascaded H-bridge rectifiers (CHBR) are an important part of the single-phase PETT. In order to ensure its reliability, an open-circuit fault diagnosis method based on the mixed logical dynamic (MLD) model and the state estimator is built for the open-circuit fault of a single IGBT. The MLD model and the state estimator of the CHBR are constructed under both normal and faulty conditions, and the residual characteristics are analyzed in the two states. Fault diagnosis is achieved according to the residuals including fault information. The proposed method requires no additional sensor. Experimental results verify the availability and accuracy of the proposed method, and the location of the fault can be accomplished in a fundamental cycle.