Offshore Wind Power Transmission Capacity and Uncertainty Assessment Based on VSC-LCC Hybrid HVDC

The offshore wind power is delivered through a hybrid high-voltage direct current line based on Voltage Source Converter and Line Commutated Converter (VSC-LCC), which can retain the advantages of Flexible High Voltage Direct Current (VSC-HVDC) while saving engineering costs, showing promising application prospects. However, the Line Commutated Converter High Voltage Direct Current (LCC-HVDC) requires a significant absorption of reactive power during operation, which deteriorates the voltage level of the receiving end grid, thus limiting the transmission of wind power. To address this issue, this paper proposes a transmission capacity analysis method for offshore wind power delivered through a multi-terminal hybrid HVDC based on AC-DC continuous power flow. Firstly, an AC system-multi-terminal HVDC power flow model considering VSC and LCC converter stations is established. Then, based on single-parameter continuous power flow and multi-parameter continuous power flow, calculation methods for the transmission capacity of a single wind farm and the joint transmission capacity of multiple wind farms are proposed. Next, considering the randomness of the receiving end grid load, a quantification method for the uncertainty of wind power transmission capacity is proposed. Finally, the validity of the proposed method is verified through a modified IEEE 30-node AC-DC system. The simulation results indicate that the transmission capacity of offshore wind power is closely related to the control strategy of LCC-HVDC and is significantly affected by the volatility of the receiving end grid load.