Protection performance assessment with grid-forming converter acting as reference generator during black-start

The studies presented in this paper aim to assess the operation of existing protective schemes (i.e. overcurrent protection) within UK networks, considering black-start scenario initiated from converter-based distributed energy sources. The primary objective is to investigate whether it is realistically feasible for a converter-based battery storage unit, to replace a synchronous generator in black-start scenarios, and deliver the same benefits accounting for adequate fault levels and reliable protection operation. The case studies include transmission and distribution level (11kV up to 400kV) fault level calculations and assessment of the protection performance under balanced/unbalanced faults considering existing settings proposed for such black-start conditions.
Furthermore, the utilization of a voltage-controlled overcurrent protection scheme is investigated as a potential protection solution, to address the reduced fault levels resulting from the converter-based source. The results and observations aim to build a solid foundation for the design of protection schemes during black-start scenarios within distribution systems.