An Optimized Hybrid Modulation Scheme for Reducing Conduction Losses in Dual Active Bridge Converters

A linearized hybrid modulation scheme for the dual active bridge (DAB) converter is proposed in this article. For the purpose of minimizing the conduction losses dissipated on the transformer and the power transistors, an optimal relationship function between the two control variables employed in extended phase shift (EPS) modulation can be derived. However, the obtained relationship function is a complex expression, which is not good for simple on-line control. Hence, a linearized modulation scheme is proposed in this article. This modulation scheme can achieve a quasi-minimum root-mean-square (rms) value of the leakage inductance current for the same output power. Meanwhile, the zero-voltage switching (ZVS) of the power transistors can be achieved over the whole power range. The power transfer capability is also kept the same as the optimal EPS scheme. Finally, experiments are conducted on a laboratory prototype to validate the effect of the linearized modulation scheme on the reduction of conduction losses. The experimental results present an improved converter efficiency and the realization of ZVS.