Frequency Support Strategy of DFIG-Based Wind Farm Based on Rotor Speed Feedforward Control and Frequency Support Capability Analysis

The frequency instability accidents in the power system with increasing renewable energy source have been observed. DFIG (doubly fed wind turbine) participating in frequency regulation has been a feasible scheme. However, the existing frequency support strategies of DFIG cannot accurately estimate its FSC (frequency support capability), and the influence mechanism of its FSD (frequency support duration) on the regulation effect is unclear as well, which makes it difficult to obtain the optimal solutions to realize the frequency support, such as APCA (active power coordinated allocation) and RSCR (rotor speed coordinated recovery). Aiming at the above problems, a frequency support strategy of DFIG-based wind farm based on rotor speed feedforward control and frequency support capability analysis is proposed. Firstly, a rotational speed feedforward control is proposed. Then, considering the change of rotor power and using the Lagrange mean value theorem to approximate mechanical power variation, the FSC of DFIG is accurately estimated, and the influence mechanism of the FSD on performance of frequency support is revealed. Next, a frequency support strategy of DFIG-based wind farm is proposed, which can realize the optimal APCA and RSCR. Finally, the effectiveness of the above methods is verified by simulations.