Functional requirements for GFC of HVDC systems and PPMs, Recommendations of GFC for connection network codes

Definition of grid-forming control concepts and control hierarchy for multi-vendor HVDC applications, for three main concepts: 1) offshore grid-forming control by offshore HVDC converters, 2) fault ride-through capabilities of offshore PPMs, 3) offshore grid-forming control by offshore PEIDs (e.g. PPMs), enabling onshore GFC by HVDC convertersFormulation of basic functional requirements for grid-forming control for the three main control chain concept, towards the interoperability of multiple parallel grid-forming devices, ensuring that the needed capabilities will be provided at the onshore and offshore connection points.