Techno-economic assessment of a low-frequency AC transmission interconnection for an offshore wind farm in Colombia

Abstract

Colombia’s Caribbean coast has substantial offshore wind potential but lacks dedicated transmission infrastructure. Although high-voltage AC (HVAC) and high-voltage DC (HVDC) are established solutions, low-frequency AC (LFAC)—the transmission of power at frequencies below the standard 50 or 60 Hz—offers a cost-effective alternative for medium-distance applications. This study assesses an LFAC system to connect a 960 MW offshore wind farm to the national 60 Hz grid under Colombian regulatory and geographic conditions. The proposed LFAC link operates at 20 Hz and includes a 75 km submarine cable, a 34 km overhead line, and a back-to-back modular multilevel converter working as a frequency conversion station. The design meets national limits on voltage regulation and unbalance, and considers efficiency, shunt currents, and transfer capability. Performance was validated using MATLAB/Simulink simulations under variable load. The economic analysis compares capital expenditure (CAPEX) and loss-related costs with HVAC and HVDC. The system achieved over 93% efficiency and complied with all voltage standards. Compared to 60 Hz HVAC, the 20 Hz LFAC enabled roughly 200% more transfer capacity and reduced shunt currents by 66%, improving stability. LFAC’s CAPEX was 9.4% higher than HVAC but 8.1% lower than HVDC. LFAC is technically and economically viable for offshore wind integration in Colombia, bridging HVAC’s reactive limitations and HVDC’s high costs, and is scalable for similar renewable projects worldwide.