Comprehensive Common Mode Equivalent Circuit Modeling of Dual Active Bridge Converter Under Asymmetric Conditions

This paper presents an equivalent common mode (CM) circuit for the Dual Active Bridge (DAB) converter, accurately capturing mixed mode (MM) behavior resulting from both asymmetric parasitic capacitances and AC-link inductances. A systematic derivation is provided, facilitating a deeper understanding of the CM noise mechanism. This derivation also enables a parametric evaluation of key reactive components (both parasitic and non-parasitic) during the design phase of DAB devices-such as H-bridges, AC-link inductances, and transformers-aiming to minimize CM noise. The proposed simplified model is compared with both a numerical switched model and a model based on the substitution theorem. The analysis focuses on the impact of AC-link asymmetry, particularly across discrete inductors, on CM noise. Experimental results are also presented to validate and demonstrate the impact of AC-link asymmetry.