Enhancing the Dynamic Performance of Current-Fed Triple-Active-Bridge DC–DC Converters Utilizing Freewheeling States for Inductor-Current Adjustment

This article provides the analytical and experimental exploration of a control strategy that enhances the dynamic performance of current-fed triple-active-bridge (CFTAB) dc–dc converters to its physical limits. So far, dynamic current transients in the inductors of CFTAB converters are poorly discussed in the literature. Published simulation and measurement results of load steps are usually plotted on a large timescale so that the fast transient behavior on switching-cycle timescale is barely visible. In this work, the freewheeling states current adjustment (FSCA) strategy is examined that reaches the new steady state as fast as physically possible. In addition to the analytical derivation of the FSCA strategy, theoretical limitations are presented and validated on a 1-kW GaN-based prototype of the CFTAB converter. Measurement results confirm that the FSCA strategy significantly reduces overshoots and oscillations. The settling time after a load step is reduced from about 1 ms down to 10 $\mu \mathrm{s}$, which yields a time reduction by a factor of 100.