Optimal Configuration of HVAC Transmission With Mid-Cable Reactance Compensation for Far-Offshore Wind Farms

The feasible transmission distance of offshore wind farms (OWFs) connected via high-voltage alternating current (HVAC) systems can be significantly extended through mid-cable reactance compensation. This paper investigates the effectiveness of such compensation and proposes an integrated methodology for optimizing HVAC transmission configurations. First, analytical expressions for voltage and current profiles along the submarine cable with mid-cable reactance are derived, providing the foundation for identifying the key constraints that limit the maximum transmission capacity (MTC). Then, an optimization model based on the DistFlow model is developed, incorporating the cable's capacitive effects. The model is formulated as a second-order cone program (SOCP), enabling accurate evaluation of the MTC in terms of rated power and transmission distance. Furthermore, a techno-economic evaluation framework is established to compare the break-even distances of various schemes, using the annualized equivalent cost (AEC) method that integrates capital investment, operation, and maintenance costs. The results show that mid-cable compensation can extend the break-even distance of HVAC systems by 10 to 100 km across different OWF capacities, thereby enhancing their suitability for far-offshore deployment. A sensitivity analysis is also performed to identify key cost drivers. Overall, the proposed approach supports optimal reactance compensation design and the selection of cost-effective HVAC transmission solutions for OWFs.