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Impact of re-synchronization strategies on the power sharing of grid-forming converters at black start

J. Rodriguez-Gongora(1), A. Ordono(2), M. González-Pérez(2), M. Zubiaga(1), A. Sanchez-Ruiz(3)

1. Department of Electronic Technology, Engineering School of Gipuzkoa, University of the Basque Country (UPV/EHU), Eibar (Spain).

2 Department of Electrical Engineering, Engineering School of Gipuzkoa, University of the Basque Country (UPV/EHU), Eibar (Spain)

3 Department of Electronic Technology, Engineering School of Vitoria-Gasteiz, University of the Basque Country (UPV/EHU), Vitoria-Gasteiz (Spain)

2026-06-27

Grid-forming (GFM) converters enable black start (BS) operation in converter-dominated power systems, where independently energized islands must be re-synchronized before interconnection. While re-synchronization is essential for stable reconnection, its impact on the power-sharing capability of GFM converters is not yet fully understood. This paper investigates how different re-synchronization algorithms affect active and reactive power sharing following island interconnection during BS. Time-domain simulations show that misalignment of internal control states and reference variables can lead to persistent power-sharing differences. In contrast, properly designed re-synchronization strategies minimize power sharing unbalances. The results highlight the importance of re-synchronization design for robust power sharing in converter-based BS applications.

Key words: Black start (BS), grid-forming (GFM), power sharing, re-synchronization.

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