Present-day Great Britain (GB) is largely reliant on thermal generation to enact electricity system restoration in the event of a national power outage. As Government policy and climate initiatives continue to the reshape GBs electricity generation mix at pace, the ability of low-carbon resources to deliver restoration services is critical to a resilient Net Zero power system. With offshore wind farms (OWFs) coming to dominate the generation capacity of the future GB system along with significant injection in battery energy storage (BESS), the complementary role of these technologies could be the key to enabling system restoration without thermal power plants.

In this paper, the performance of an HVDC-connected OWF (HVDC-OWF) in a supporting role to GB system restoration is explored. Electromagnetic transient modelling and simulation in PSCAD is undertaken to facilitate the analysis. The restoration solution under study is based on an onshore grid-connected BESS as the primary restoration provider, enabled by grid-forming control (GFM), with the HVDC-OWF supporting the process through the delivery of active and reactive power. Two HVDC-OWF control strategies are evaluated, with the onshore HVDC converter station adopting either grid-following (GFL) or GFM (without energy transfer) implementations. Both approaches consider the offshore turbines as being limited to conventional GFL capability. The analysis sets out to investigate the energisation requirements of the HVDC-OWF from the BESS as the primary restoration provider, before assessing their coordinated performance in system restoration. To facilitate the restoration analysis, a portion of SP Energy Networks’ transmission system is modelled in the Edinburgh region of central Scotland. A restoration pathway is defined to study energisation phenomena related to the connection of grid transformers, overhead lines, shunt reactors, and block loads. The analysis finds that the GFL HVDC-OWF control strategy is more susceptible to interaction instability with the weak AC system as the restoration process initially evolves, without sufficient BESS stability support. Thus, while both control strategies demonstrate the potential of combined BESS and HVDC-OWF restoration solutions in GB, the stronger voltage support and stability margins offered by the GFM-based HVDC-OWF makes it favourable for early-stage restoration support.