Small-Signal Impedance Modeling and Stability Analysis of BDFIG Tied into Weak Power Grid

Brushless doubly fed induction generator (BDFIG) is a potential alternative to the well-known DFIG in wind power generation field due to its high reliability and low maintenance cost in virtue of the elimination of brushes and slip rings. However, the stability issue of BDFIG-based wind power system under weak grid still leaves unknown. To settle such problem, this paper establishes the input admittance model of the BDFIG system in the generic vector synchronous frame, where the influence of current control loop and phase-locked loop (PLL) are considered. Then the interaction between the BDFIG system and the weak power grid is evaluated and discussed. To be specific, the effect of the control parameters on the system stability is analyzed in detail by applying the generalized Nyquist criterion (GNC). The correctness of the theoretical analysis is finally verified by simulations.