Research on Coordinated Control Strategy for Supplying Offshore Wind Farms to Passive Networks Based on Hybrid Dc Transmission Technology

This paper proposes a coordination control strategy for an offshore wind farm linked to a hybrid DC transmission system, emphasizing the collaboration between the wind farm and the Line-Commutated Converter (LCC) on the rectifier side. The LCC is connected to the wind farm and plays a key role in regulating active power transfer to the hybrid DC system. A Voltage-Source Converter (VSC) is located on the inverter side, connecting the system to the passive network, and it is responsible for maintaining voltage stability in the network. The primary objective of the control strategy is to ensure efficient and stable power delivery from the wind farm to the grid. On the LCC side, current control is employed to regulate the active power output from the wind farm. As LCC cannot directly control reactive power, it adjusts the current to match the active power demand from the wind farm. A ProportionalIntegral (PI) controller is used to maintain stable active power transmission, ensuring that the wind farm and the hybrid DC system are synchronized. The VSC is responsible for maintaining voltage stability within the passive network. It utilizes a PI controller to adjust the output voltage and mitigate any fluctuations in the network. This regulation of voltage not only helps stabilize the system but also indirectly addresses the reactive power demands. Meanwhile, the LCC is responsible for controlling the flow of active power. The coordination between the wind farm and LCC is crucial for achieving optimal power flow and voltage stability. The strategy has been implemented and validated through simulation in PSCAD/EMTDC, with results showing effective power coordination and voltage regulation. The proposed method demonstrates feasibility for offshore wind farm applications, ensuring reliable and stable power delivery to the grid.