Comparison of wind farm topologies for offshore applications

Increasing energy demand and environmental factors are driving the need for the green energy sources. The trend, in general, with respect to wind farms is to increase the number and the size of wind farms. The wind farms are also being located offshore with the prospect of more consistent and higher energy capture. The offshore wind farms are likely to move farther off from the shores to reduce visual impacts and increase the size. But, this has implications in terms of design of the collection grid and grid interconnection. Farms of 1 GW size and at distances of about 100 km are envisaged [1]. The design of collection system and turbine interconnection will become very important as the farms move farther offshore. Proper choice of collection system topology is important from the point of view of maximum energy capture while ensuring a high reliability of the design. Different collection system topologies have been proposed by researchers before, with the radial system being most popular. One of the key factors in selection would be the losses in the farm. In order to select the most suitable topology a comparison of different topologies with respect to losses, reliability and costs has to be done. Comparisons of calculations indicate that the DC series and series-parallel wind farm design may be options for future wind farm designs. The DC series and series-parallel design have lower reliability, but can be improved by providing redundancies. The designs have equipment costs almost equal to the AC wind farm costs. The losses in DC series-parallel wind farm are higher by about 12 % when compared to AC wind farms. The DC series design is also very attractive design, but has restrictions with respect to insulation. Also, the required turbine ratings may be significantly and unrealistically high when it comes to designing large wind farms. It can also be concluded that the novel designs require significant amount of work before these can be used in real wind farms.