Coordinated Frequency Regulation Method for Offshore Wind Farm Connected Through an HVDC Link Based on Droop Control

Abstract

AbstractIn order to suppress the disturbance of the frequency of the onshore AC power grid due to the grid connection of offshore wind farm, this paper proposes a coordinated control method of frequency support of offshore wind farm connected through an HVDC link based on droop control, and establishes a simulation system of measurement-feedback-adjustment of nearest level approximation modulation (MFR-NLM) of onshore converter station and offshore converter station. Firstly, the simulation model of offshore wind farm connected through an HVDC link system is established, and the model uses modular multilevel converter (MMC) and NLM modulation. Secondly, the mathematical function expression of the DC voltage setting signal and the measured value of the voltage, the frequency setting signal and the measured value of the frequency are constructed based on the droop control method. Finally, the improved recent level modulation method of the additional DC voltage controller and frequency controller are designed to realize a new type of measurement-feedback-regulation control of onshore converter stations and offshore converter stations. The simulation results show that the proposed method can convert the AC frequency signal and the DC voltage signal to each other, so that the offshore wind farm can change the power output according to the frequency deviation, and realize the frequency support of the onshore AC power grid.KeywordsOffshore Wind FarmHVDCDroop ControlFrequency Support