The characteristics of DC impedance interface

as an interconnection interface of AC/DC hybrid power supply system

of voltage source converter（VSC） may be affected by AC network

which will bring new stability problems. To realize the accurate analysis of DC stability in AC/DC hybrid power supply system connected with weak AC grid

we established a small-signal DC impedance model considering the influence of grid impedance and system delay

analyzed the influence of control parameters and system parameters

and proposed that the influence of AC grid impedance and system delay on DC impedance characteristics of VSC will reduce DC stability. Based on the analysis of system control circuit and the coupling relationship between AC and DC side

the key factors affecting DC impedance characteristics were determined

and an active damping method was further proposed to improve the DC stability. Finally

a simulation model of AC/DC hybrid power supply system was developed

and the accuracy of proposed stability analysis and active damping method was verified.