In order to establish a model of impedance stability analysis for high frequency isolated AC-DC link

this paper proposes a modeling method of the DC side small-signal impedance of high frequency isolated AC-DC link（VSC-LLC） by integrated coupling design of voltage source converter（VSC） and LLC resonant converter. Firstly

the constant gain voltage clamping function of LLC resonant converter under the operating mode of approximate resonance point is combined to realize single-stage unified control strategy

and VSC and LLC are combined into one stage. Secondly

combined with the fourth-order small-signal model of LLC resonant converter under the fundamental wave approximation method

the small-signal model of VSC-LLC is established

and the DC side impedance model of the VSC-LLC is derived

by which the impedance modeling of the two-stage system is realized. Finally

a nonlinear time domain simulation model of VSC-LLC is established on the Matlab/Simulink. Simulation results have verified the correctness of the proposed DC side impedance modeling method

and the influences of circuit parameters and controller parameters on DC side impedance are also analyzed

which provides a theoretical basis for impedance stability analysis of microgrid based on high frequency isolated AC-DC link.