VSC-HVDC would have some influences on AC short-circuit current level. On the basis of the topological structure of VSC-HVDC and the characteristics of its control system

we analyzed the characteristics and mechanism of AC short-circuit current contributed by VSC-HVDC

and proposed a mathematical model and calculation method of AC short-circuit current contributed by VSC-HVDC. The short-circuit current contributed by VSC-HVDC is the sum of the three-phase short-circuit currents contributed by all VSC inverters connected to the short-circuit point. The positive and negative sequence short-circuit currents can be limited under the regulation of its current inner loop controller. The zero-sequence short-circuit current is determined by zero-sequence network

which is formed by the transformer（Y-side） and AC grid. Finally

the correctness of the analyses in this paper is verified by the waveforms of simulation and actual short-circuit fault of Xiamen HVDC project.