润色下面的电机工程学报论文GFM-GCI系统正序、负序电压电流环控制框图如图3a、b所示。正序无功下垂控制环的输出U+作为并网点正序d轴电压给定值负序无功下垂控制环的输出U -作为并网点负序d轴电压给定值并网点正序q轴电压给定值和负序q轴电压给定值均为0。通过正、负序q轴电压环的PI控制器将正负序的并网点q轴电压始终控制为0即GFM-GCI的输出电压始终与同步旋转坐标系的d轴重合。

The control block diagrams for the positive-sequence and negative-sequence voltage-current loops of the GFM-GCI system are shown in Figure 3(a) and (b) respectively. The output U+ of the positive-sequence reactive power droop control loop is used as the reference value for the positive-sequence d-axis voltage at the grid connection point. The output U- of the negative-sequence reactive power droop control loop is used as the reference value for the negative-sequence d-axis voltage at the grid connection point. The reference values for the positive-sequence and negative-sequence q-axis voltages at the grid connection point are both set to 0. By using PI controllers for the positive-sequence and negative-sequence q-axis voltage loops, the positive-sequence and negative-sequence q-axis voltages at the grid connection point are always controlled to 0. Therefore, the output voltage of the GFM-GCI system always aligns with the d-axis of the synchronous rotating coordinate system