Open-circuit Fault Diagnosis for Parallel Operated Full-bridge Isolated DC-DC Converter

Single-phase power electronic traction transformer (PETT) is the power device to realize higher efficiency and reduction of weight in railway traction system, and parallel operated full-bridge isolated DC-DC converters are an important part of single-phase PETT to realize a stable DC-voltage output. In order to ensure the reliability of DC-DC level, in this paper, an open-circuit fault diagnosis method based on state estimator was proposed for open-circuit fault of a single IGBT. Through establishment of mixed logic dynamic (MLD) model and state estimator model, estimator residuals of the DC-DC level were analyzed under normal and faulty conditions. According to the residuals including information of the fault, fault diagnosis was achieved. Finally, the proposed fault diagnosis method was verified in a hardware-in-loop (HIL) experimental platform with RT-LAB simulator. Experimental results show that the diagnosis method can effectively locate the fault switch in four switching cycles after open-circuit fault of IGBT.