计算自然坐标系下的序阻抗，暂时没有添加信号输入(The calculation of the sequence impedance in the natural coordinate system)

基于序阻抗的直驱风电场次同步振荡分析与锁相环参数优化设计((impedance modeling +PLL modeling) sequence impedance of direct drive wind power farm subsynchronous oscillation analysis and parameter optimization design based on PLL)