Transient Synchronization Stability Analysis of the Grid-integrated DFIG

The phase-locked loop (PLL) is widely used in DFIG to achieve synchronization with the power grid. In this paper, the large-signal reduced-order model of the PLL-synchronized DFIG during the symmetric fault is established. Then, the transient synchronization stability (TSS) analysis is conducted using the proposed analytical criterion. The TSS mechanism of the grid-connected DFIG system is revealed when subjected to the voltage dip and the phase jump during the fault. Meanwhile, the TSS index is proposed to reflect the TSS level of the grid-connected DFIG system during the fault. Moreover, the impact of PLL’s parameters on the TSS of the system is also conducted using the phase portrait method. Finally, the time-domain electromagnetic transient simulations are conducted in Matlab/Simulation software to validate the effectiveness of the theoretical analysis.