High-Frequency Transient DC-Bias Current Suppression Methods in Triple-Active- Bridge Converters

Abstract

Triple-active-bridge (TAB) converters have attracted considerable attention due to their commendable electrical isolation, high energy density, and bidirectional energy transmission capabilities. Nevertheless, one critical issue for TAB converters is the high-frequency transient dc-bias current (HFTDC) due to the volt-second imbalance under various dynamic conditions such as the startup, power reversal, and sudden load or output voltage change. Main consequences resulting from HFTDC include increased current stresses, causing magnetic saturation of the converter and posing a risk of damage to power electronics components. After reviewing main strategies of suppressing HFTDC especially for complicated TAB converters, a general mathematical model of TAB converters was developed and consequently a universal HFTDC suppression strategy based on flux-balancing principle and superposition analysis was proposed. The proposed strategy can effectively realize the power decoupling and lower the implementation difficulty. In addition, the advantages of the proposed strategy are also reflected in its versatility for various modulation techniques, as well as its ability to adapt to various dynamic scenarios, including load changes, power fluctuations, power reversal, and startup processes. Both simulation and experimental evaluations under various scenarios are provided to validate the feasibility of the proposed method.