Frequency control strategy for sending-end of hybrid cascaded UHVDC system with large-scale wind power access

Abstract

For the frequency overrun problem caused by the high proportion of wind power in the sending grid of hybrid UHVDC transmission system, the coordinated frequency control strategy of wind power and hybrid UHVDC system in the sending system is proposed. Firstly, the additional frequency control strategy considering primary frequency control and inertia characteristics is introduced in the wind turbines and the line commuted converter (LCC) station respectively, and the virtual inertia control strategy is introduced in the modular multilevel converter (MMC) station. Secondly, the action rules and control strategy of wind power and hybrid UHVDC system coordination involved in the power grid are designed. At the same time, the mechanism of frequency control strategy is analyzed​ based on the frequency response model of wind power and UHVDC integrated system. Finally, the simulation results indicate that the proposed frequency control strategy can enhance the inertia and primary frequency capability of the AC system at the sending end, and effectively improve the frequency stability problem of the AC system under different operating conditions.