We studied the influence level of wind farm clusters at different locations under the same parameter variation range. Taking a large doubly fed induction generator（DFIG） based series-compensated transmission system in North China as a prototype; we adopted three DFIGs to represent wind farm clusters at different locations and established a linearized model of the whole system. Subsynchronous resonance（SSR） modes were determined through a participation factor method. The impact levels of dominant factors

such as rotor speed

output power

number of DFIG

and line resistance

by multiple wind farms at different locations were compared. Results show that the wind farm cluster with shorter electrical distance from busbar has greater impact on system stability than wind farm cluster with longer distance under the same parameter variation range. The impact of the number of wind turbines which are put into operation is nonlinear and it depends on the rotor speed. System stability and resonance frequency increase as the impedance of transmission lines between wind farm clusters and collection bus increases.