BorWin1 - First Experiences with harmonic interactions in converter dominated grids

During the year 2013 the power infeed from offshore wind turbines increased. As BorWin1 is the first HVDC system which connects an offshore wind farm by a small islanded offshore AC grid some phenomena occur. The frequency dependent grid impedance is due to the used assets significantly different from onshore grids. Thus, common methods of investigation during the planning phase are not sufficient and have to be extended. Converters can go into resonance with grid natural frequencies of the grid and oscillations with high frequencies can arise. The paper presents some occurred phenomena and new methods of investigation. Different methods to identify harmonic stability problems are compared and advantages as well as disadvantages are mentioned.