说明：  基于SOGI（2阶广义积分器）的单相锁相环simulink仿真，参考《光伏与风力发电系统并网变换器》周克亮译 71页
(Based on SOGI (2-order generalized integrator) single-phase phase-locked loop simulink simulation, refer to Grid Converters for Photovoltaic and Wind Power Systems translated by Zhou Keliang ,page 71)