Steady-State DC Offsets Suppression of the Dual Active Bridge Converter for More-Electric Aircraft Applications

The paper analyses the steady-state DC offset currents on both sides of the high-frequency transformer in a dual-active bridge (DAB) converter for more-electric aircraft (MEA) applications. These converters are widely used for high voltage-ratio power transfer between 270 and 28V DC buses, as well as for bidirectional energy exchange with storage devices. However, mismatched resistances in different commutation paths introduce DC components into the AC current waveforms on both sides of the converter. This effect is further exacerbated on the low voltage (LV) side due to the high voltage ratio, potentially leading to increased losses and performance degradation. To address this issue, this paper firstly developed a comprehensive model through detailed analysis of different operation modes of the DAB converter. Then, using this model, a proportion integration (PI) controller and a moving discretized control set model predictive control (MDCS-MPC) controller have been proposed and designed. A comparison is presented to illustrate the steady-state control performances between both control strategies. Both PI and MDCS-MPC controllers can mitigate the DC offset issue, but it seems MDCS-MPS is with much faster response. These findings have been validated with thorough simulation and experimental studies.