Grid-following and grid-forming technology options for Corinth - Kos HVDC interconnection

The Corinth-Kos MMC VSC HVDC link will interconnect the Dodecane complex of islands with the mainland Hellenic Electricity Transmission System (HETS) and will need to operate either in parallel to a weak AC interconnection or even as the only grid-forming resource of the Dodecane interconnection. This paper analyses the options of operating the HVDC converters at Kos Island either in grid-following (GFL) or in grid-forming (GFM) mode. While both options are feasible, they necessitate different types of reinforcements. The GFL option necessitates the presence of local resources such as synchronous condensers but it does not require a Dynamic Braking Module (chopper), which is necessary in the GFM case. It is also shown that the GFM option can facilitate the coordination of the HVDC active power recovery after a fault with RES plants that are planned to be installed in the Dodecane area.