Dual-Mode DCBP-LLC Converter With Integrated Fault-Tolerance for More-Electric Aircraft Bipolar DC Power Systems

To ensure a reliable power supply for critical onboard avionics in more-electric aircraft (MEA) bipolar DC systems, this paper presents a dual-mode diode-clamped bridge parallel LLC (DCBP-LLC) converter integrated with voltage self-balancing and monopolar fault ride-through capability. Under a single pole-to-ground fault (SGF), the converter reconfigures the primary-side bridge to isolate the faulty pole while maintaining continuous power delivery through the healthy pole. During normal bipolar operation, two additional control variables, namely the duty-cycle ratio \Delta d and the phase-shift angle \theta, are introduced to regulate the neutral-point current and achieve accurate power sharing between the positive and negative buses. A comprehensive analysis of voltage gain characteristics and soft-switching boundaries is conducted, based on which a seamless mode-transition strategy is developed in this paper. Simulation and experimental results obtained from a 1-kW prototype (±270 VDC input/28 VDC output) validate the effectiveness of the proposed strategy. Peak efficiencies of 92.4% in the normal bipolar mode (NBM) and 94.6% in the fault-tolerant monopolar mode (FMM) are achieved, together with robust fault ride-through performance and minimal transient deviation.