Research And Design Of Internal Collection Grid Topology For Large Offshore Wind Farms

Renewable energy, especially wind power has made tremendousdevelopment in the world in response to today’s increasingly seriousenergy crisis and environmental degration. Offsore wind power has thecharacteristics such as high wind speed, little windshear as well as stabledominant wind direction compared with onshore wind power.Meanwhile, the capacity of offshore wind turbines is usually higherand does not take the precious land resources. Due to the advantagesmentioned above, the offshore wind farm has become a hot topic for bothdomestic and foreigner researchers. Offshore wind energy has maderemarkable advance with the development of offshore wind technology.Those operating offshore wind farms now are all AC wind farms,most of which have a small capacity as well as simple topology. Theinternal collection grid of AC wind farms is often designed byresearchers based on experience. With the increase of wind farm capacityand distance from the coast, the design of wind farm internal collectiongrid has become more and more important. This paper focuses on theoptimal design of wind farm internal collection grid, and the researchsub-topics and the contribution of the work are listed in the following:(1)Since the theoretical research of AC offshore wind farm internalcollection grid has become relatively mature, this work takes theDenmark’s Horns Rev offshore wind farm as an example and analyzesthe advantages as well as the disadvantages of different topologies. Basedon the analysis above, this work gives an introduction of DC offshorewind farm topologies, and compares the internal loss, economy andreliability parameters of DC offshore wind farm by analyzing a DC windfarm model.(2)This work gives a detailed introduction of the topology of DC-DCconverters suitable for wind turbines, especially those most commonly used turbines based on PWM rectifier and DC-DC Converter. Byanalyzing the operating principles of DC offshore wind farm, the controlstrategy of wind turbine rectifier and DC-DC converters, we can get theoperational principle of the DC offshore wind farms.(3)In order to verify the control strategy of DC wind turbines and DCoffshore wind farms under differernt conditions, this work builds a DCoffshore wind farm model conisisting of3*3DC wind turbines in thesoftware PSCAD/EMTDC. With the assistance of this simulation model,the validity of the control strategy has been confirmed.