In order to clarify the coupling relationship of fault information transmission characteristics in AC/DC hybrid system, a simplified model of DC system with electrical quantity transmission characteristics is established. Based on the switching function transfer theory, the law of fault information transmission on AC and DC sides is analyzed. On this basis, the dynamic phasor theory is introduced. Considering the steady-state, symmetrical and asymmetrical fault conditions, a simplified model of DC system is established based on the equivalent impedance of DC system and the control system. Combined with the simulation verification, the accuracy of the simplified model is verified by comparing with the detailed model. According to the general law of fault information transmission characteristics, the theoretical basis is provided for the follow-up research on the backup protection principle of AC/DC hybrid system.

HVDC, transfer characteristics, simplified model