1.Department of Electrical Engineering, Tsinghua University, Beijing100084, China;2.State Key Laboratory of HVDC (Electric Power Research Institute of China Southern Power Grid Company Limited), Guangzhou510663, China

To achieve economy and efficiency in the power collection of the 10 GW-level offshore wind power base from multiple low-frequency AC transmission channels and seamless connection with onshore DC transmission lines, this paper proposes a concept of the large-scale offshore wind power hub and its implementation method. Each offshore low-frequency AC transmission channel is connected to the corresponding interface unit of the power hub after reaching the shore. The core of the interface unit is a simple flexible diode rectifier, which converts the low-frequency AC input of the corresponding channel into DC and integrates it into the DC bus. The flexible diode rectifier interface can provide flexibility and controllability, while maintaining low cost and compactness, allowing each input interface unit to achieve independent black start and power control. The power from all input channels is collected on the DC bus of the hub which can be directly connected to subsequent onshore DC lines for transmission to the load center. This paper proposes and analyzes the topology, basic design principles, and control strategies of the offshore wind power hub. Compared with existing offshore low-frequency AC wind power transmission schemes, the proposed power hub scheme has better economy, reliability, and compactness. The effectiveness of the proposed offshore wind power hub is verified by simulation results.