Efficiency Optimization Scheme for Isolated Triple Active Bridge DC–DC Converter With Full Soft-Switching and Minimized RMS Current

This article performs a comprehensive steady-state performance optimization for the isolated triple active bridge (TAB) dc–dc converter adopting the five-variable modulation (FVM) technique. First of all, a universal analytical model suitable for all the hardware conditions of the TAB converter is established using frequency-domain analysis method. Second, considering the influence of port voltages and the energy stored in parasitic capacitances, a simplified and accurate zero-voltage switching (ZVS) constraint is derived without complicated condition judgments. Based on this, aiming at reducing the overall system losses, a comprehensive efficiency optimization modulation scheme with FVM is proposed in this article. Distinct from the previous optimization methods, the proposed scheme is not only a multiobjective optimization with minimized circulating current level and full-ZVS operation. It is also a generic optimization scheme covering all the five operation modes, and there is no individual optimization for each mode, which greatly simplifies difficulty of implementation. Afterward, to overcome the cumbersome optimization process, an advanced particle swarm optimization algorithm is used to seek the global optimal operating point in the entire power flowing range. Extensive simulation is carried out using MATLAB/Simulink. And the steady-state characteristics of the proposed scheme are fully compared with the traditional phase shift modulation method. Finally, a 1.2 kW laboratory platform is built. A significant efficiency improvement under light-load condition up to 21% is achieved, which substantiates the feasibility of the proposed optimization scheme.