A Novel Coordinated Transient Frequency Support Strategy of All-DC Wind Power System

All-DC system is very promising for long-distance collection and transmission of large-scale offshore wind power. However, it inevitably results in frequency stability issues of the power system, especially with the increasing penetration of wind power. To solve this problem, a novel coordinated transient frequency support strategy of the all-DC wind power system is proposed in this paper. The proposed strategy includes a frequency trajectory planning (FTP) control of the DC wind turbine (DCWT) and an energy curve-based inertia support control of the HVDC system. The former is mainly used to suppress the frequency nadir based on the kinetic energy of DCWT rotors, while the latter fully utilizes the energy margin of capacitors to decrease the peak of the rate of change of frequency (RoCoF). With this strategy, various energy storage devices in the all-DC system can be fully and rationally utilized to achieve optimal frequency support of the power system. Finally, simulation results verify the effectiveness and superiority of the proposed transient frequency support strategy.