Impedance-Reshaping-Based Controller Design for Stability Enhancement in Triple-Active-Bridge Converters With Constant-Power Loads

Triple-active-bridge (TAB) converters are key multiport hubs in DC systems, but constant-power loads (CPLs) and cross-port coupling can induce oscillations and erode stability margins. This article presents a stability-oriented and optimization-based impedance-reshaping controller design for TAB converters that retains the standard PI structure while systematically tuning the gains to meet interface stability requirements. The design directly targets the port output impedance and reshapes it in both magnitude and phase over a specified frequency band by minimizing the ℓ 2 norm objective. This band-limited magnitude–phase shaping focuses on the impedance-interaction region responsible for CPL-driven instability, enlarging the Nyquist stability margin and improving tolerance to interface uncertainty. Compared with conventional approaches, the proposed method requires no additional control path and no prior knowledge of CPLs’ control strategies or parameters, facilitating practical deployment in multiconverter systems. Simulation and hardware experiments validate the approach, demonstrating elimination of oscillations, enlarged stability margins, and robustness of TAB converter systems.