Study On Offshore Wind Farms Flexible Direct Current Transmission Based On Voltage Source Converters

Along with the global economy development, the energy crisis is growing more serious. The traditional energy, because of whose limited reserves and caused a lot of pollution, prompted people to develop renewable new energy. As a kind of renewable energy, Wind power has abundant reserves in the global range, coupled with growing shortage of land resources and rich wind energy storage on offshore areas, vigorously developing offshore wind business has become an important method to solve the energy crisis. Flexible HVDC transmission technology over the traditional technology has many advantages. It will be widely used in the transmission of the offshore wind farm and grid connection, which has become the key of offshore wind power development.This topic studies flexible high voltage direct current transmission based on voltage source converter which called VSC-HVDC system. According to the basic working principle of VSC-HVDC, this paper carries the parameters of the main circuit and filter on the detailed analysis and calculation. Then based on synchronization reference frame (d-q department), this paper designs the double loop vector control system for the offshore wind farms flexible HVDC converter, realized the active power and reactive power independent control. And in the light of converter requirements of the high power applications by flexible HVDC system, this paper designs the new module multilevel converter (MMC) and takes the method of weighting balance signals on reference and the method of sorting capacitance together to solve dc voltage sharing problem which existed in MMC. Using simulation software Matlab/Simulink simulates the designed topology structure and control mode of VSC-HVDC and MMC, simulation results confirm the main circuit and filtering system parameter selection rational and the control method effectiveFinally, using the TMS320F28335DSP which provided by TI Company as a control chip to built VSC-HVDC experiment system, wrote the DSP program On the double closed loop vector control, at the same time, based on PLC and touch screen interface, designs corresponding communication system and the experiments show the validity of the method which adopted by this paper.The research of this topic has certain theoretical and practical significance for offshore wind farms VSC-HVDC system theory research. It is helpful for the further development of the more system to realize the industrialization of the offshore wind farms VSC-HVDC transmission system in our country.