Investment cost of HVAC cable reactive power compensation off-shore

High voltage, underwater AC cables are often used to transmit the power generated by an offshore wind farm to the main grid onshore. High charging currents in such cables require reactive compensation at cable ends in order to extend the transmission distance. This paper analyses the investment cost related to the design of the offshore reactive compensation strategy, trying to give guidelines about the most favorable techniques. Both concentrated compensation by means of dedicated reactor and distributed compensation using the power electronics converters embedded in the offshore generation units are considered. It is shown that in general, a proper blend of both compensation strategies leads to minimum investment cost. Besides being dependent on the individual component costs, the relative amount of concentrated and distributed compensation yielding minimum cost depends strongly on the physical layout of the particular wind farm.