Meeting Great Britain’s (GB) 2050 net zero targets requires major transmission upgrades, including new onshore and offshore infrastructure to support large-scale offshore wind integration. National Energy System Operator’s (NESO) Pathway to 2030 Holistic Network Design (HND) outlines a coordinated plan to integrate offshore wind, introducing additional HVDC links and moving toward a hybrid AC/DC offshore grid. A comprehensive set of energisation, steady-state, and dynamic performance scenarios are assessed to support NESO with recommendations on operational requirements. Time-domain steady-state analysis is carried out to study control performance across nominal ranges of voltage and power, and to assess the coordinated response of the parallel HVDC-OWF systems to AC voltage and frequency events. The steady-state analysis is further complemented by frequency-domain studies, including AC impedance scans, to support stability assessment and resonance identification. The dynamic performance of the system was evaluated across a range of disturbance scenarios, including onshore and offshore AC faults, DC faults, HVDC converter blocking events, and wind farm disconnections. The outcomes of the studies, some of which are included in this paper, provide NESO with operational guidance on potential implications of such schemes in the GB system.

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