The Application Of Offshore Wind Farm Connected With Grid Through VSC-HVDC

With the arrival of the 21st century, renewable energy technologies, especially wind power technology has been unprecedented development. There have been a large number of offshore wind farm in coastal areas. With the appearing of offshore wind farm, the availability wind power capacity increase largely. Offshore wind power capacity is about 3 times than the capacity of land. The offshore wind farms that are far away from the coast have many problems in the traditional ways of connecting with grid through AC system, such as reactive power compensation. In this paper, the method that offshore wind power system based DFIG connecting with the grid through VSC-HVDC is studied. The simulation of the whole system is performed through PSCAD / EMTDC.First, in this paper the theory and application of offshore wind farm that constituted by DFIG connecting with grid through VSC-HVDC is discussed. The development status and trends of the VSC-HVDC technology in domestic and overseas is particular analyzed. Additional the technology of connection between the DFIG wind power generation system and VSC-HVDC is given a simple analysis. Further more, a simple introduction of the tool PSCAD / EMTDC using in the simulation is given.Secondly, the DFIG wind power generation technology is particular introduced and the characteristics of wind farm based on DFIG is described. A detailed derivation of the mathematical model for DFIG wind power farm that includes wind turbine, DFIG,transmission and so on is given. Based on derivation of the detailed mathematical model this paper gives control strategy of rotor side and grid-side converter in order to providing theoretical basis for the simulation.Again, the basic structure of VSC-HVDC system is studied in this paper. Based on the analysis of the structure, this paper using method of mathematical model gives a detailed description of VSC- HVDC system. It solves the theoretical basis of the VSC-HVDC system for offshore wind farm through analysis of VSC-HVDC mathematical model and study of system interface circuit to give control strategy of the details VSC-HVDC system. In addition, this paper gives a brief analysis for the DFIG interconnected with VSC-HVDC coordination control.Finally, the simulation and analysis for offshore wind farm connected with grid through VSC-HVDC system using software PSCAD / EMTDC is given. Then, the work of the offshore wind farm connected with grid through VSC-HVDC transmission system is studied under the action of the wind based on the basic wind, gradient wind, the wind disturbance and the gust wind. Also the simulation of the system is given in the situation of some common power grid failure.