说明：  单相光伏并网发电系统电压前馈控制和有源频率偏移（AFD）孤岛检测法的simulink仿真模型，初步实现了并网电流与电网电压的同频同相，AFD孤岛检测方法采用S函数给出，检测功能基本实现。
(Single-phase grid-connected PV system voltage feedforward control and active frequency offset (AFD) simulink simulation model islanding detection method, the initial realization of grid current and the grid voltage of the same frequency and phase, AFD islanding detection method using the S function to out detection realized.)