Enhancement of a Control Concept for Parallel HVDC Link Operation to Increase Flexibility for Offshore Wind Park Grid Connections

The ongoing growth of offshore wind parks (WP) worldwide will lead to increasingly more complex offshore grid structures in the long term, requiring high-voltage direct current (HVDC) control concepts for their connections towards onshore. As such, these concepts are the main focus of the governmental funded German "North Seas Offshore Network II" (NSON II) project, considering the offshore WP development in the German North Sea. This paper presents the accordingly adapted offshore HVDC control concept for AC-side parallel HVDC link operation and in detail compares the behavioral differences in case of direct offshore converter terminal coupling and coupling across own transformers. Negative impacts are obtained regarding unequal power distribution and the mapping of individual converter power limitations, thus control concept enhancements are suggested, assessed and successfully tested, aiming at control concept usage in more complex AC-side meshed offshore grids studied further on within NSON II.