Today, grid code requirements for the generators are prepared keeping the power system stability needs in focus, considering the capabilities of each type of generation. Owing to the specific characteristics of the DRU-HVDC, offshore wind farm requires fundamental changes in the controls of the wind turbines and the offshore wind farm itself in order to operate while connected to the DRU. Therefore, in this deliverable both the DRU specific operational requirements and power system stability requirements are given. The operational requirements aim at fundamental functional operation of the offshore wind farm when connected to the DRU, while the stability requirements aim at support to the offshore and onshore grids, especially in case of disturbances (e.g. faults, frequency drops).

To address this topic, deliverable 3.1 is divided into four main sections, each looking at a different aspect. In order to define the interfaces and hierarchical structures for the given requirements, in chapter 2, case specifications for two exemplary topologies (one radial, one offshore AC-interconnected) are presented. In chapter 3, events and operational states are specified, which will help interoperability of offshore wind farms from different vendors, followed by chapter 4, in which system stability requirements, which are related to offshore AC, onshore AC and also DC, are given, where the existing grid codes have been utilized as references. Finally, in chapter 5 a generic wind turbine model and offshore wind farm layout is provided as a basis for further work.

Overall, the main objective of Work Package 3 is to identify and specify appropriate analyses and tests to demonstrate the interoperability of the wind turbine generator and offshore wind farm controls when connected to DRU-HVDC, as wells as development and demonstration of compliance evaluation procedures.