Small signal stability analysis and control of the wind turbine with the direct-drive permanent magnet generator integrated to the grid

In this paper, a model of the wind turbine (WT) with direct-drive permanent magnet generator (DDPMG) and its associated controllers is presented, based on which a small signal stability analysis model is derived. The small signal stability analysis shows that the WT with DDPMG without the controllers is stable, and the controller can improve the small signal stability of the WT system. To evaluate the control capability of the proposed controller, simulations are performed on a single machine infinite bus system and a four-machine system, and the dynamic responses of the DDPMG are compared with those of the WT with doubly fed induction generator (DFIG). Under the system disturbance, the dynamic performances of the DDPMG are better than those of the WT with DFIG. The impact of the WT with DDPMG and the WT with DFIG on the transient stability of the power system is also investigated in term of critical clear time (CCT). The transient stability margin of the system can be improved with the integration of the WT systems, while between these two WT systems, the stability of the power system with the WT with DDPMG is further enhanced.