While wind power generation is developing rapidly all through the world， there are more and more megawatt grad wind farms being connected directly into the power system. In this paper， on the base of traditional RX model for wind power flow calculation， a new continuation power flow calculation model is established using theπ-type equivalent circuit of asynchronous wind turbine. Based on the proposed model， total transfer capability（TTC） of power system containing large-scale wind farms is investigated under the constraint condition of static voltage stability. The calculation results show that the variations of wind speed have a great influence on TTC. Especially when the penetration power is increasing， the effect of wind speed on TTC of power system will become more notable.