Off-Shore Windpower – Grid connection and Reliability

This Ph.D. project is carried out at Dong Energy in cooperation with Risø National Laboratory and Aalborg University.

The aim of the PhD project is to investigate the influence of wind generation on the reliability of power systems. This task is particularly important for large offshore wind installations, because failure of a large wind farm will have significant influence on the balance in the power system, and because offshore sites are normally more difficult to access than onshore installations. The reliability of power production from a wind farm depends on wind speed conditions, the wind turbines themselves, the system layout and the grid connection; besides, the offshore environment poses new challenges to face for the installers.

The project has been divided into three parts. Firstly, a model for yearly generation assessment of offshore wind farms has been developed: this model includes wind speed randomness and variability, components (e.g. wind turbines, internal cables and connectors to shore) failures, influence of site environment and some minor aspects of relevance. Secondly, this model has been used for evaluating the so-called HLI analysis (Hierarchical Level I), where the system adequacy to supply the load is assessed. The power system under study includes conventional power plants, an aggregated load and distributed generation together with offshore wind generation, whereas transmission facilities are neglected in this type of simulation. These two assessments are performed considering a sequential Monte Carlo simulation: this approach has shown more flexibility and completeness in the analysis of wind generation than analytical techniques.

With these two models, that are currently available, some sensitivity analyses will be carried out in the next months. Besides, some of the models will be used for performing an HLII analysis: in this type of study, the transmission facilities are included in the power system model and the adequacy of the system generation is evaluated including the availability of transmission lines and cables.

All analyses in the project are carried out by the use of the software Matlab and the power system analysis tool Power Factory from DigSILENT: simulations will include steady-state conditions as well as dedicated reliability analyses.