Abstract: For the active support application requirements of new energy grid connection, a two-stage structure consisting of a three-phase full bridge AC-DC converter and a dual active bridge (DAB) converter is selected as the research object. Under the influence of parasitic capacitance of devices, DAB converters will face the problem of difficulty in achieving soft switching, and in wide voltage range applications, traditional extended phase shift (EPS) control will bring significant reactive power circulation problems when it is far from the unit voltage gain point. Therefore, a topology structure and its modulation method are proposed, which injects additional excitation current by adding an excitation inductor to ensure the full load range soft switching of the DAB converter. At the same time, traditional EPS control is improved to ensure efficient energy transmission over a wide voltage range. Finally, an experimental prototype of a 20kW all SiC device is built to conduct steady-state testing and soft switching performance testing on the device, verifying the effectiveness of the proposed method.

Key words: active support, vehicle-to-network(V2N), dual active bridge (DAB) converter, soft switching