Advanced power electronics for cable connection of offshore wind

Several offshore wind farms are planned in a number of locations in Northern Europe. The introduction of offshore wind power brings the wind power into a new era, characterized by larger size of the farms, 200 – 1000 MW are planned, and increasing distances from the grid. Cable transmission is the only solution for the transmission from the farm to the shore. Often land cables are also required to reach a sufficiently strong interconnection point in the grid. Together this gives transmission distances of 50 – 100 km. The scale of these installations together with the interaction between the wind generators and the grid requires an overall understanding of the entire system. System knowledge and good models can identify the technical challenges but also find robust and economical solutions. Extruded AC or DC cables combined with power electronics such as HVDC Light and SVC Light gives the required flexibility and robustness. For short distances AC cables and FACTS devices such as SVC Light is normally found to be the best solution. For longer distances HVDC Light is increasingly attractive. This is particularly true given the increased size of the wind installations and the recent development of the HVDC Light technology. The technical benefits of the HVDC Light technology for wind power applications have been known for many years and also been demonstrated in small test installations. Examples of these benefits: Superior power quality mitigation in the AC grid, isolation of the wind generators from faults in the AC grid. The technical development has resulted in large converters offering drastically improved cost/performance including improved efficiency. The technology is also proven in a number of full-scale installations including offshore applications for gas platforms in the North Sea. All this together give a perfect fit between offshore wind farms advanced cable and power semiconductor technology. Trend in offshore wind farms Offshore wind farms have been in operation since the beginning of the 1990’s. In the meantime the size have increased so the largest offshore wind farms have power ratings equivalent to medium sized power plants. The development is described in Figure 1 1.00 10.00 100.0