Optimal Design and Operation of Long-Distance Deep-Water HVAC Transmission for Offshore WECS Integration With FPSO Unit

Abstract

This paper evaluates the technical feasibility of integrating an offshore wind energy conversion system (WECS) into a floating production storage and offloading (FPSO) unit. The WECS is situated closer to the Brazilian mainland, requiring a 150 km long subsea umbilical cable for the integration with the FPSO unit. High voltage alternating current (HVAC) transmission is mandatory due to the substantial water depths, introducing challenges such as power losses and significant reactive capacitive current generated by the cable. This paper proposes a comprehensive approach to dealing with these challenges. Firstly, the umbilical cable section is sized based on ampacity and maximum current under short-circuit conditions. A power flow optimization is thus employed to determine the optimal transmission voltage that minimizes power losses. The optimization results define the reactive power that the back-to-back converter of the WECS must absorb based on the active power. This relationship is represented as a lookup table control, which ensures efficient operation by adjusting the reactive power reference in the WECS power control unit. Using this approach, the WECS back-to-back converter compensates for a portion of the reactive power generated by the umbilical, reducing the need for additional infrastructure such as shunt reactors or reactive compensation substations. Each component of the system is modeled, and a complete simulation is conducted using MATLAB/Simulink to validate the proposal. The results demonstrate the effectiveness of this approach in enhancing system efficiency while significantly reducing carbon dioxide emissions during oil and gas exploration through the integration of WECS with FPSO units.