说明：  先dq变换然后构建电压外环电流内环的双闭环系统，实现了statcom的前馈解耦控制。可以解决大负载投入的电压降落问题。
(First, dq transform is used to construct the double closed-loop system of voltage outer loop and current inner loop, which realizes the feedforward decoupling control of STATCOM. It can solve the voltage drop problem of large load input.)