Analysis, Detection, and Faulty Winding Localization for Interturn Short-Circuits in Medium-Frequency Transformer of a Dual-Active-Bridge Under Multiple Modulation Schemes

In literature, interturn short-circuit (ITSC) faults owing to insulation degradation in medium-frequency transformers (MFTs) of dual-active-bridge (DAB) converters are characterized by voltage stress from various phase-shift modulation (PSM) schemes. However, the impact of ITSC faults on the DAB with multiple PSM schemes, aiming to develop a robust detection and faulty winding localization, has received limited attention. To address the missing link, a generalized harmonic model incorporating magnetizing inductance under ITSC fault is presented to analyze the DAB converter with various PSM schemes. Thereafter, a two-stage method is developed for early 1% incipient ITSC fault detection and faulty winding localization using sensors integrated for DAB control. Firstly, a robust ITSC fault detection is achieved by monitoring deviations in the most sensitive healthy peak of the magnetizing current using a software-based window comparator and counter scheme. Subsequently, a faulty winding localization algorithm is applied after fault detection to facilitate effective troubleshooting. The localization scheme utilizes primary current and output voltage as key indicators. Accurate localization of the faulty winding is achieved at 1% ITSC fault by employing a software-based band-pass filter and RMS detector to capture subtle primary current deviations. The proposed method demonstrates robustness against load transients, noise, and switch faults.