EHV AC interconnection for a GW-size offshore wind-farm cluster: Preliminary sizing

The recent availability of XLPE-insulated, 400 kV-50 Hz submarine cables, in single- or three-core construction, suggests to investigate the ac shore connection of GW-sized offshore wind-farm (OWF) clusters. The paper discusses some basic features of a 200 km long 400 kV-50 Hz cable system, connecting to the grid three large OWFs with 2 GW total capacity. After selecting suitable cables based on their active power transfer capacity, a shunt compensation plan for the resulting system is proposed, taking into account maximum exploitation of the longest cable stretch as well as no-load system operation. A simple but effective approximate algorithm for the optimal exploitation of the cable system by OWF voltage control is proposed; simulations show the viability of the interconnector and of the proposed algorithm for several different loading conditions. Results evidence good steady-state performances, with small reactive surplus and, notably, full-load losses not exceeding 3%.