Fixed duty cycle compensation and magnetizing current design for DAB DC-DC converter with conventional trapezoidal modulation to achieve zero voltage switching

The conventional trapezoidal modulation (TZM) control can ensure dual active bridge (DAB) DC-DC converters work without non-active power, resulting in low circulating loss. However, zero voltage switching (ZVS) capability for half of the power switches is lost. To achieve ZVS for all the power switches, fixed duty cycle compensation and magnetizing current design are proposed in this paper. It is suited for the dual active bridge DC-DC converter with TZM control, of which four power switches cannot achieve ZVS. The fixed duty cycle compensation is applied to create small bias current to ensure ZVS of the two switches in one bridge leg regardless of the load. ZVS of the other two power switches is obtained by the magnetizing current design. As a result, all the power switches of dual active bridge DC-DC converter can achieve ZVS and four switches can be turned off with very low current. A 1.6kW laboratory prototype is built to verify the effectiveness of the proposed method.