Operating Range Analysis of Dual Active Bridge Converters in FRT-Buck Modulation Mode

The FRT-Buck modulation of three-phase dual active bridge (DAB3) converters features soft-switching characteristics and current-limiting capability, which is a critical approach to realizing fault ride-through (FRT) operation of DC distribution grids. In this paper, the operating ranges of DAB3 converters under FRT-Buck modulation are first studied. According to current limitations, this paper divides the operating ranges of DAB3 converters into three different types. Then, the operating trajectories of DAB3 are studied under different operating conditions. In addition, the heat map of transmission power is given under constraints. Finally, the actual peaking values of three-phase currents and elliptical operating trajectories are validated on the MATLAB/Simulink platform. The simulation results confirm the accuracy of the theoretical derivation. The proposed method can determine the operating point of the DAB3 in post-fault operations and assist the design of protection schemes for DC distribution grids.