Input Impedance Modeling Method for Dual Active Bridge Converters under Broadband Perturbation

The dual active bridge (DAB) is a widely used DC-DC topology owing to its ease of control and ability to achieve various control objectives. When designing a DAB-based system under broadband perturbations, one must model the DAB, calculate its input impedance, and analyze the system stability. In this study, two continuous-time impedance models of the DAB, i.e., a reduced-order model named the power-based impedance model (PBIM) and a full-order model named the generalized state-space average impedance model (GSSAM), are proposed and used to calculate the input impedance in a single-phase modulation mode. The modeling errors are analyzed, the participation factors and residuals are calculated, and a Bode diagram is constructed to illustrate the change in the input impedance with increasing leakage inductance. Simulations are conducted using various circuit parameters to verify the results. The results show that the PBIM exhibits simplicity and accuracy in the low-frequency domain, whereas the GSSAM performs better in the high-frequency domain.