Research on Transient and Steady‐State Coordinated Control Strategy for Two‐Stage DC/DC Converter

ABSTRACT This paper focuses on the 270 V/28 V DC power distribution architecture for more electric aircraft, aiming to resolve the inherent trade‐off between steady‐state efficiency and dynamic response in conventional two‐stage DC/DC converters. A bidirectional converter based on the Buck–Boost + LLC topology and its coordinated control strategy are investigated. The proposed scheme integrates both steady‐state and transient control. In steady‐state operation, the Buck–Boost stage adopts variable‐frequency control to achieve soft switching, whereas the full‐bridge LLC resonant converter operates at a fixed frequency to minimize power loss. During transient conditions, dynamic pulse regulation is implemented based on state‐plane analysis of the full‐bridge LLC resonant converter, enabling fast operating‐point transition along the optimal trajectory and achieving superior coordination between efficiency and dynamic performance. Simulation and experimental results demonstrate that the converter maintains stable output over a wide input range of 230–290 V, with an overall efficiency exceeding 90% and full‐range soft switching for all power switches. Under load step changes, the absolute output voltage deviation is reduced by 113 mV (37.7% reduction) during light‐to‐heavy load transition and by 120 mV (42.9% reduction) during heavy‐to‐light load transition. Relative to the rated 28 V output voltage, the deviations are reduced by 0.41% and 0.43% under the two operating conditions, respectively. In addition, the settling time is shortened by 10 ms (33% performance improvement) in both cases, with smooth and unique transient response trajectories. The proposed solution effectively improves dynamic response at the millisecond level while guaranteeing high efficiency and stable operation.