Reconfigurable H5-bridge Based LLC-DAB Sigma Converter for EV Fast Charging Stations

In fast charging stations, the electric vehicle (EV) charger needs to adapt to the traction batteries of different models. The ultra-wide voltage range brings significant challenges to the optimal design of the dc/dc converter in the EV charger. To cope with this issue, we propose a Sigma converter based on a reconfigurable H5 bridge. The converter consists of two submodules, the LLC submodule and the DAB submodule, with a shared H5 bridge. By reconfiguring the H5 bridge, the LLC submodule exhibits a trapezoidal gain characteristic. On this basis, the DAB submodule realizes the residual gain through a hybrid modulation. The LLC submodule delivers the majority of power and always operates at the optimal operating point, while the voltage regulation is majorly realized by the DAB submodule. The circulating current of the LLC submodule contributes to the zero-voltage switching (ZVS) of the DAB, and the partial power processing structure makes the power path simpler and more efficient. In addition, the modulation method is capable of battery current control, making it suitable for EV charging applications. A 3.3kW prototype that converts 800V input to a 150-900V ultra-wide output is designed, simulated, and experimentally tested to validate the concept.