Offshore wind power has promising development potential, and reliable and efficient large-scale distant offshore wind power grid integration system is the key technology to develop the offshore wind power. Aiming at the miniaturization problem of offshore platform for distant offshore wind power HVDC transmission system, an HVDC transmission scheme for the grid-following medium-frequency distant offshore wind farm is proposed. This scheme utilizes the grid-following wind turbines, where the modular multilevel converters (MMCs) are installed on both the rectifier side and the inverter side of HVDC system. Firstly, the grid-following medium-frequency scheme is described from two aspects of topology and control system. Then, the influence of the offshore AC system operation frequency on the offshore wind farm and its HVDC transmission system is analyzed, including influence on the transformer, the AC cable and the MMC. Based on a ±320 kV/1 000 MW offshore wind power HVDC transmission system, the technical and economic efficiency of the proposed 100 Hz grid-following medium-frequency scheme is analyzed, including the main circuit parameters of key electrical equipment, the cost of AC cable, the cost of offshore platform, the cost of wind turbines, the AC cable loss and rectifier station valve loss, and the transmission capability of AC cables. Finally, an electromagnetic transient simulation model of the grid-following medium-frequency scheme is built in PSCAD/EMTDC to verify the effectiveness of the scheme. © 2021 Automation of Electric Power Systems Press.
