Challenges and Solutions in Integrating Black Start into Offshore Wind Farms

Power systems are currently experiencing a transition towards decarbonisation of electrical generation through large-scale deployment of renewable energy sources. These are gradually replacing conventional thermal power plants. Consequently, in case of a total/partial blackout, conventional black-start resources are not ready for operation. Offshore wind farms, with their large capacity and fast controllers, show potential as innovative black-start units. This introduces the need of a new design for the wind power system. In this paper, challenges and possible solutions in integrating black start service into offshore wind farm will be presented. A first challenge is represented by the implementation of a black-start unit. The black-start unit should be capable of forming the wind farm power island, withstanding transient phenomena due to energisation. There could be several different solutions, e.g. the integration of grid-forming converters in the wind farm design. These could be battery energy storage systems (BESSs) and/or new generation grid-forming wind turbines. The selected challenges are analysed using simulation on a wind farm, and the proposed solutions discussed. It can be concluded that a system comprised of BESS, grid-forming wind turbines and STATCOM, in combination with novel technologies such as virtual synchronous machine, soft-charging, harmonic active filtering, etc. represent a good proposal for the integration of black start into offshore wind farms.