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Blackstart from HVDC-connected Offshore Wind: Hard vs Soft Energization

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posted on 15.09.2020 by Anubhav Jain, Oscar Saborío-Romano, Jayachandra Naidu Sakamuri, Nicolaos Antonio Cutululis
In recent years, renewable energy sources have been integrated on a large scale in power systems all around the world to address the environmental sustainability concerns. With conventional thermal generators being phased out, large offshore wind power plants present a viable alternative to provide blackstart services for power system restoration. In this paper, by means of simulations, grid-forming wind turbines are shown to successfully energize the offshore transformer and the HVDC export link in a controlled manner, to ultimately supply the onshore grid. Two methods for energizing the offshore network have been compared:
the prevalent hard-switching approach and the more complex soft-start method. Additionally, control has been implemented to mitigate the significant transients in the export link associated with pre-charging of the onshore converter. It is shown that soft-start can provide faster energization with smaller transients compared to hard-switching. Moreover, the sensitivity analyses performed
in this study illustrate the impact of pre-insertion resistor design and voltage ramp-up rates on transients during hard-switching and soft-start, respectively. The results presented in the paper also show that a separate controlled pre-charging stage of the onshore converter from its DC terminals is essential for the safe energization and operation of the export link.

The manuscript has been accepted for publication in IET Renewable Power Generation.

Funding

Innovative tools for offshore wind and DC grids

European Commission

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History

Email Address of Submitting Author

anub@dtu.dk

ORCID of Submitting Author

0000-0002-6264-0906

Submitting Author's Institution

DTU Wind Energy

Submitting Author's Country

Denmark

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