Coordinated frequency control scheme of offshore wind farm connected to VSC-HVDC

Abstract

This article presents a coordinated control scheme enabling the voltage source converter-based high-voltage direct current (VSC-HVDC) transmission system connected offshore wind farm to provide frequency response. Once the onshore system frequency deviates, the proposed control strategy will be activated so that both the wind farm and the VSC-HVDC can work together to provide frequency support. In this approach, each wind turbine should operate in de-loading mode to acquire reserve under normal condition. On detecting the frequency event, not only the reserve and kinetic energy of each wind turbine can be utilized for frequency regulation by adjusting rotor speed, but the DC capacitor installed in the VSC-HVDC is arranged to participate in frequency control by slightly changing the DC-link voltage as well. The superior performance of the proposed control method has been verified by simulation.