说明：  搭建完整的双馈风力发电系统，模拟网侧控制和转子侧控制，观察电压跌落情况下，双馈风力系统的变化
(A complete doubly fed wind power generation system is developed to simulate the grid side control and the rotor side control, and to observe the change of DFIG wind system under voltage sag)