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, th