Studies On Low Voltage Ride Through Of Variable Speed Constant Frequency Wind Turbines

In recently years, our country’s wind power industry development rapidly. From2006to2010, Wind power installed capacity annual average growth rate of more than100%. However, with increasing wind power penetration, traditional strategy which removal the wind farm when the voltage drop is no longer able to meet the requirements of grid stability, so the new grid requirements that the new wind turbine must have low voltage ride through capability. This paper mainly research the Crowbar protection of the VSCF wind turbines, analyzing the low-voltage characteristics of a local grid, appling the selected program in the local low-voltage grid.First, this paper describes the two types wind turbines which is belong to variable speed constant frequency wind turbines. And then, I detail analysis their characteristics and control principles of each module, building their both transient model in Matlab/Simulink.Second, I briefly introduce the measures through the domestic and international, detailed analysis and comparison of the now extensive use of various Crowbar protections, choose different types of Crowbar protection program and make improvements. After comparison, I chose that the active Crowbar protection programs, which add some delay to prevent the Crowbar protection in case of many switching in power fault I chose Crowbar protection used unloading resistance for direct-drive permanent magnet wind turbines, and also change the grid side converter control strategy, which can provide maximum reactive power to the grid, supporting the grid voltage recovery. Simulation results show that these two programs can well protected fan, the fan achieve a low voltage ride through.Finally, for a domestic local power grid which includes many large-capacity wind farms, assuming their reactive power full use of compensation capacitor, respectively Simulate the voltage drop to the rated voltage of90%and20%of the wind farm’s responses, to determine whether they have the capability of low voltage ride through. The Crowbar protection is applied to the local power grid, indicating the effectiveness of programs and necessity of Crowbar protection, and meaning while give some suggestions for the local power grid to improve the low voltage ride through capability.