In recent years, wind power generation has attracted extensive attention because of its advantages such as large reserves and environmental friendliness. Among them, doubly fed induction generator (DFIG) is the most widely used type of wind turbine. There are generally two control modes, namely, the Current Controlled DFIG (CC-DFIG) and the Voltage-Controlled DFIG (VC-DFIG). CC-DFIG using the phase locked loop (PLL) to synchronous with the grid while VC-DIFG using the power loop instead. In this paper, the input admittance models of DFIG under two different modes are established, and the effects of different power grid strength and control parameters on system stability are studied by using the generalized Nyquist steady-state criterion. It is concluded that the VC-DFIG system has good adaptability of control parameters under weak grid. Finally, the correctness of the above theoretical analysis is verified by simulation.
 

VC-DFIG; CC-DFIG; Input Admittance; Stability Analysis