Among renewables shared around the globe, offshore wind is projected to increase in the coming decades, reaching almost 1000GW capacity by 2050. In today’s transitioning power systems, ensuring a high level of reliability is crucial to prevent outages that can jeopardize grid stability and result in substantial economic losses. Despite the efforts to enhance reliability, the occurrence of a blackout necessitates the implementation of an effective restoration plan, commonly known as the black-start procedure, to return the grid to normal operation. With the dynamics of the grid rapidly changing due to the large-scale phasing out of synchronous generators, there is a greater need and interest in the market for providing black start as a service to the grid. Offshore wind farms (OWFs), equipped with their substantial capacity and efficient controllers, can serve as innovative black start units based on renewable energy, offering the advantage of both large-scale power generation and rapid response capabilities. The feasibility of providing black start services from an OWF remains to be demonstrated and is particularly relevant when considering that the OWF is operated off-grid and involves an electrolyser unit with the capability to respond proportionally to frequency variations, enhancing its adaptability to the evolving grid dynamics.

The hybrid of using traditional grid-following (GFL) wind turbines (WT)s along with an external power source (e.g. diesel generator or energy storage) for black start have been investigated. An equipment able to self-start (i.e., energisation without relying on the transmission grid) is the highest priority requirement being demanded and grid-forming (GFM) converters with their inherent quality can achieve this, supporting the transition towards 100 % renewable-based black start strategy.

In an off-grid islanded system with a bottom-up restoration approach, incorporating primary frequency control (PFC) enhances the efficiency of large-scale offshore wind energy utilization and, also be beneficial for a Battery Energy Storage System (BESS) in OWFs. The electrolyzer units can act as PFC service providers reducing the burden on the BESS. These dynamic electrolyzer’s offer dual benefits: Firstly, during wind turbine startup, they convert excess electricity into green hydrogen, reducing BESS dependence. Secondly, the BESS is strategically preserved for controlled power modulation during soft-start and transient events. This integrated strategy improves system efficiency, contributes to green hydrogen production's economic viability, providing an approach to offshore wind power storage and utilization.

This paper discusses the utilization of an electrolyzer unit for providing the necessary support as a PFC tackling the challenges for integration of a BESS equipped with GFM control into an islanded off-grid OWF to perform black start service work in parallel with GFL WTs using a soft-start approach. There is a notable absence of challenges addressed with energization procedure of an islanded off-grid OWF placing the BESS at the offshore platform and utilizing the electrolyzer unit for a black start process. The simulations developed using Matlab/Simulink, allow the adoption of a black start procedure and the verification of the islanding operation of the off-grid OWF with wind-speed variations. Additionally, a parallel feeder energization is shown using an already energized feeder. Conclusions on sizing of BESS is drawn.