In order to study dynamical voltage stability of wind farms cluster, in this paper, the dynamic model of wind farm with active power fluctuation is established in DIgSILENT/Power factory. The traditional differential algebra equation (DAE) model is improved. A dynamic analysis method is proposed which combines the continuation power flow (CPF) and time domain simulation (TDS) method based on bifurcation theory. A fast algorithm is proposed for computing the stability margin of the system, and the proposed method tracks the two dimensional Hopf bifurcation (HB) curves of system by using a two parameter so-called ‘two-step’ method. It analyses and compares the dynamic response properties and voltage control capability of the wind cable set area between different power compensation devices. The simulation results of a certain WFC in Hami, Xinjiang Province indicate that the stability margin of saddle node bifurcation (SNB) based on static continuation method is more optimistic than HB based on CPF combined with dynamic TDS. The proposed analytical method is a fast direct method to obtain the HB, as well as can calculate voltage stability limit of wind farm accurately. This work is supported by National Natural Science Foundation of China (No. 51277056), National Key Technology Program (No. 2015BAA01B01 and No. 2015BAA01B02), and Key Laboratory of Photovoltaic Technology of Qinghai Province (No. 2014-Z-Y34A).