Modeling Analysis, and Online Detection of Interturn Short-Circuit Fault in Medium-Frequency Transformer of Dual-Active-Bridge Converter

The strident working condition of the dual-active-bridge (DAB) converter has elevated the risk of interturn short-circuit fault (ITTSCF) in medium-frequency transformer (MFT). Thus, it is crucial to analyze the DAB converter under ITTSCF in MFT to avoid the complete winding short-circuit due to insulation failure. Thus, the presented work analyses the variations in the magnetizing and leakage inductance of MFT ranging from low to high severity levels of ITTSCF. Thereafter, its impact on the current stress, power transfer, and zero-voltage-switching (ZVS) of the DAB converter is presented in detail. Based on the analysis, this article presents a new reliable online ITTSCF detection technique for MFT in a DAB converter. This technique utilizes the root-mean-square (RMS) and average-based fault indices generated from the magnetizing current of MFT. The proposed fault detection technique is effective even at low severity ITTSCF (i.e., as low as 1% ITTSCF) and utilizes an off-the-shelf magnetizing current sensor to avoid extra cost. The proposed fault detection technique is immune to load variation and major switch faults in the DAB converter and thereby increases the reliability. For validation, the MFT is designed with winding taps and integrated with the hardware prototype of the DAB converter.