Analysis of DC Fault for Dual-Active Bridge DC/DC Converter Including Prototype Verification

Abstract

This paper presents dc fault analysis for a dual-active bridge (DAB) dc/dc converter which comprises two active bridges and an internal medium frequency transformer. This topology provides galvanic isolation, voltage step up/down and bidirectional power transfer. The dc fault study assumes the dc terminal voltage of the converter is at zero. The steady-state fault current is limited to a low magnitude which is less than the rated value without any controller action depending on the design of the converter. The dc fault current magnitudes are analyzed with ac equivalent circuit where only the fundamental component of the ac voltages and inductor current are considered. Phase shift and ac voltage magnitude modulation control methods are selected. A detailed DAB dc/dc converter 3-MW, 4-/40-kV-based system is simulated using MATLAB/Simulink to validate the proposed analytical study. Further, hardware testing is conducted to confirm the dc fault studies with a 500-W 24-/100-V prototype.