不平衡电网条件下建模与仿真研究

Research on Modeling and Simulation of DFIG under Unbalanced Grid Conditions

为了准确分析不平衡电网条件下,DFIG机组使用传统矢量控制策略而引发控制能力下降的原因,并改善DFIG机组的故障穿越能力,建立了DFIG机组转子侧变换器和网侧变换器的数学模型。首先分析了故障下DFIG机组的动态变化过程。针对电网电压不对称故障,在Simulink环境下搭建了基于双d-q正、负序分解的转子侧及网侧变换器模型,并将传统的控制策略与改进控制策略进行仿真对比。仿真结果表明,改进的控制策略可以有效地抑制有功、无功的二倍频波动,减小过电压和过电流,增强机组对电网故障冲击承受能力,提高DFIG机组运行的稳定性。

For analyzing the weakening control ability of DFIG which use the traditional vector control strategy under unbalanced grid conditions and improve the fault ride-through capability,the mathematical model are established for the rotor side and the grid side converter of DFIG. The dynamic behaviors of DFIG during asymmetrical grid fault are firstly analyzed. The rotor side and the grid side converter are modeled based on double d-q positive and negative sequence decomposition in Simulink and the simulation results are compared with the traditional one. The results show that the oscillation of power output could be effectively restrained with this improved control strategy. The over current and voltage of the rotor winding are also reduced. Moreover,the endurance ability and operating stability are enhanced.