Comprehensive Online Decoupling Strategy for LC-TAB Converters in EVs Considering Voltage Fluctuation During Load Transient

Power coupling between the ports is a significant challenge faced by triple-active-bridge (TAB) converters. The existing power decoupling strategies only consider the impact of phase-shift angles on power coupling and compensate only for the phase-shift angles to achieve decoupling power control. While these strategies exhibit good decoupling characteristics under constant-voltage-load condition, the magnetic flux of three port transformers is also closely aligned with port voltages. Under constant-resistance-load or constant-power-load conditions, the decoupling effects of conventional strategies would be deteriorated due to fluctuant port voltages, degrading the applicability. To address the above issue, this article presents a comprehensive online decoupling strategy for the TAB converter with LC resonant cavity, where the coupling effect of phase-shift angles and output voltages are comprehensively considered, allowing for a superior decoupling effect under various load types. Herein, the slopes of coupling factors with respect to the output are analyzed and are compensated to zero to achieve decoupling. Furthermore, the fixed-point iteration method is introduced to simplify the calculation process, enabling online decoupling. Finally, a 1-kW experimental prototype is built to validate the proposed strategy, where, compared with the existing strategy, the power fluctuations caused by coupling have been decreased by an average of 30%.