The Research Of Converter In Direct-Drive Wind Power Generation System

As the world's fastest growing renewable energy source, wind energy has drawn worldwide attention. Due to high efficiency, simple structure and stable operation, variable speed constant frequency (VSCF) direct-drive wind power generation system using permanent magnet synchronous generator (PMSG) is the development trend and one of the focuses of wind power generation system, on which this paper researches through theory analysis and simulation.Firstly, dual PWM converter is selected to be the power converter of 10kW direct-drive wind power generation system based on PMSG after comparing common topological structures of direct-drive wind power generation system because the generator-side converter and grid-side converter can be controlled separately. And the device parameters of main circuit of dual PWM converter are optimal designed.Secondly, successful control strategy of dual PWM converter is the key technology for direct-drive wind power generation system. Double closed loop control scheme of dual PWM converter based on PI regulator is designed and improved feedforward control scheme is researched in order to improve the robustness of grid-side converter to disturbances from both grid voltage amplitude fluctuation (symmetry) and load variation.On the other hand, with the increasing of wind turbines, the response of wind turbine is more and more important when the grid voltage dips. Therefore, the control schemes of grid-side converter of wind power generation system under unbalanced grid voltage dips are studied on the basis of analyzing the influences of unbalanced grid voltage dips on the controller of grid-side converter. The responses of grid-side converter under unbalanced grid voltage dips with traditional vector current controller and dual vector current controller are analyzed contrastively. The results show that grid-side converter with dual vector current controller can keep connected to the grid under unbalanced voltage dips and wind power generation system has good performance under grid voltage dips in a short time.In this paper, models of PMSG and dual PWM converter with their controllers are set up by Matlab/Simulink. In addition, experiments are made on the simulation platform of VSCF wind power generation system. The behavior of dual PWM converter is demonstrated by simulations and experiment and the control strategy is valid and correct.