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The papers in this special section focus on HVDC systems for large offshore wind power plants. These plants have experienced an important growth in the last decade and are becoming a key energy source worldwide. Offshore wind presents clear advantages due to high and stable wind speeds offshore, enabling the use of larger wind turbines than those commonly used on inland wind power plants. However, transmitting power to load centres also brings a number of technical challenges. Depending on the distance to the shore and the power rating, AC or DC technology may be the preferable option for integrating offshore wind power to onshore grids. There are a number of issues which have to be considered requiring substantial research and development. For DC connections, (Voltage Source Converter) VSC-HVDC technology has shown advantages over (Line Commutated Converter) LCC-HVDC. The development of multiterminal HVDC grids though brings further challenges related to system operation, control, and protection and coordination between HVDC converters, wind power plants, and the onshore system. The development of power electronic switches has reached a point where the size, rating, and the system efficiency can meet the needs of commercial HVDC. Wind power plants connected to HVDC transmission system require specific control and protection coordination between HVDC converters and wind turbines.