Characterization of Frequency Stability in Power System with Large-Scale DFIG Wind Farms

This paper investigates the changing nature of frequency stability problem in wind-rich power systems. The published studies on frequency stability with wind power generation have mainly used simple power system models and frequency nadir as the metric. This approach is not sufficient to characterise the impact on frequency stability with wind power generation. In this study, active power vs. frequency response characteristics is used to evaluate the frequency stability of a large power system. A systematic methodology is followed to investigate the frequency stability with high wind power generation based on the doubly-fed induction generator (DFIG) technology. Therefore, steady-state system parameters, such as active and reactive power generation and terminal voltages are maintained constant when integrating DFIG wind farms into the network. The results show that the integration of DFIGs with inertia and active power controls has two significant positive effects in the frequency arresting period. Firstly, with the DFIG wind generation, power system can regulate frequency in the fast-transient period of the frequency regulation dynamics which was not possible with the synchronous generator. Secondly, the total deceleration torque of the system has decreased due to the fast and the improved response of DFIGs which ultimately leads to improved frequency stability as it reduces the maximum frequency drop. Therefore, integrating DFIG wind farms with appropriate controls would improve power system frequency stability.