This paper presents a time-domain analytical framework for DC-terminal short-circuit fault analysis in Triple Active Bridge (TAB) DC–DC converters. Unlike prior harmonic-domain approaches limited to post-fault steady-state behavior, the proposed method captures both transient and steady-state fault dynamics under open-loop operation. Closed-form expressions for instantaneous, peak, and RMS leakage-inductor currents are derived, accounting for phase-shift modulation, port-voltage imbalance, and leakage-inductance redistribution. The analysis shows that fault current severity is strongly dependent on pre-fault operating conditions, even with fixed hardware parameters. Analytical, simulation, and experimental results validate the proposed framework, which provides practical guidance for semiconductor rating, transformer leakage design, and reliable TAB operation under dc-side faults.
