AC/DC converter with DC fault suppression for aircraft +/- 270 VDC distribution systems

The increasing electrical demand in commercial and military aircraft justifies a growing need for higher voltage DC primary distribution systems. A DC system offers reduced power losses and space savings, which is of major importance for aircraft manufacturers. At present, challenges associated with DC systems include reliable fast acting short circuit protection. Solid State Contactors (SSC) have gained wide acceptance in traditional 28 VDC secondary systems for DC fault interruption. However, the reliable operation at higher operating voltages and currents requires further technology maturation. This paper examines a supporting method to SSC for more reliable fault mitigation by investigating bidirectional AC/DC converter topology with DC fault current blocking capability. Replacement of semiconductor switches with full bridge cells allows instant reversal of voltage polarities to limit rapid capacitor discharge and machine inductive currents. Demonstration of this capability is realized by tracking DC fault currents in time-domain simulations of a ±270 VDC converter dynamic model built in MATLAB-Simulink. Simulation results have shown that the modified power converter topology provides a fast response to DC faults and it can be considered as a back-up to SSCs in clearing faults in ±270 VDC distribution systems.