Control for High Power Dual Active Bridge DC/DC Converter during DC fault

This paper presents the DC fault control for a dual active bridge DC/DC converter which comprises of two active bridges and an internal medium frequency transformer. This topology provides galvanic isolation, voltage stepping, bidirectional power transfer and capability of soft switching. The control is focused on the converter DC terminals fault and reactive current circulation. Two control methods are considered namely, the phase shift angle between the two AC voltages and the Sinusoidal-Pulse width modulation method on the individual bridge branches of the converter to control the power flow and the AC voltage magnitude, respectively. A closed-loop control strategy is proposed to regulate the power level transfer, reactive current circulation and fault current magnitude. The controller exhibits good performance during several cases including DC faults. A dual active bridge DC/DC converter 3 MW, 4/40 kV based system is simulated using MATLAB/Simulink to validate the proposed control system.