Matrix interconnected topology for dc collector systems of offshore wind farms

This paper describes a matrix interconnected topology for the dc collector system of an offshore wind farm. Compared to a series-parallel dc collector topology, the proposed matrix collector system can mitigate overvoltage and over current phenomena of wind turbine-generator units subsequent to bypassing/isolation of a faulty unit. The matrix interconnection also allows harvesting of maximum power from a wind farm when the faulty unit is isolated. The proposed topology is equipped with extra switches between the paralleled branches of dc collector system. These switches enable the collector system to change topologically, which in turn leads to overvoltage mitigation on failure conditions. Later, as a solution to over current problem that may arise due to topology change, a control strategy has been described. To investigate the topology, the turbine-generators of a wind farm have been modeled as power sources. The proposed model and control strategy are applied to a study system to investigate capabilities and features of the proposed matrix topology compared to a series-parallel collector system. The results of investigation show that in addition to overvoltage mitigation, the matrix topology can reduce the amount of over current down to a desired level via control of the dc current of the wind farm transmission system. Also, the maximum power capture is realized on failure occurrences.