电网不对称故障下永磁同步风电机组低电压过渡的研究

Low Voltage Ride-through of Permanent Magnet Synchronous Wind Turbine Under Asymmetrical Grid Faults

电网导则要求并网风电机组在电网电压一定的跌落范围内不脱网运行。为了满足这一要求,建立了永磁同步发电机组网侧变流器的数学模型,分析了电网不对称故障时风电机组直流侧电压的波动机理,采用瞬时对称分量法求得网侧三相电压的正序和负序分量,在解耦控制中分别控制正序和负序分量。仿真结果表明,改进后的控制策略保持了逆变器三相电流对称,消除了直流侧二倍工频纹波,实现了电网不对称故障下风电机组的低电压过渡。

Grid-connection standards require the wind turbine to ensure no off-grid operation within a certain range when the grid voltage drops.In order to meet this requirement,a mathematical model of the permanent magnet synchronous generator grid-side converter was established.Fluctuation mechanism on DC voltage were studied when asymmetry faults took place.The instantaneous symmetrical components method was applied to detect the positive and negative sequence components of grid voltage sag.The positive and negative sequence components were controled through respective channel.Simulation results show that the improved control strategy keeps symmetry of inverter three phase current,eliminates the quadratic fluctuations of DC voltage,relizes LVRT in condition of asymmetrical fault.