润色下面论文中文图4和图5分别给出了单相接地短路故障后并网点电压正序分量跌落至07pu时采用传统控制策略和采用本发明控制方法时构网型并网变流器系统的仿真波形对比图。 、 分别为构网型并网变流器系统输出的正序无功功率和负序无功功率i+ d+和i+ q+为构网型并网变流器系统输出电流正序dq轴分量i- d-和i- q-为构网型并网变流器系统输出电流负序dq轴分量。图4为采用传统控制策略时的仿真波形图图

The simulation waveforms of the grid-forming grid-connected inverter system using traditional control strategy and the control method proposed in this invention are compared in Figure 4 and Figure 5, respectively, when the positive sequence component of the grid voltage drops to 0.7pu after a single-phase grounded short circuit fault. The positive and negative sequence reactive power output by the grid-forming grid-connected inverter system, as well as the positive sequence dq-axis components of the output current (i+d+ and i+q+) and the negative sequence dq-axis components of the output current (i-d- and i-q-), are shown in the figures. Figure 4 shows the simulation waveform when the traditional control strategy is used, and the fault occurs at 1.5s as indicated in the figure. It can be seen from the figure that when the grid experiences an asymmetric fault, there is a deviation between the actual reactive power output and the set value, indicating that the actual reactive power value of the system cannot accurately follow the command value. Figure 5 shows the simulation waveform when the novel reactive power droop control strategy proposed in this invention is used. It can be seen from the figure that under the condition of grid voltage asymmetrical fault, the positive and negative sequence reactive power output by the grid-forming grid-connected inverter system can accurately follow the set value, effectively injecting positive and negative sequence reactive currents into the grid according to grid requirements, and improving the dynamic reactive support capability of the system during faults. Therefore, the proposed control strategy effectively controls the reactive power output of the grid-forming grid-connected inverter system, enabling the injection of appropriate positive and negative sequence reactive currents into the grid according to grid requirements, and realizing full-process grid-forming control during faults.

In summary, the method for traversing asymmetrical faults in grid-forming grid-connected inverter systems disclosed in this invention ensures stable operation of the system when the grid experiences asymmetrical faults, and has the following beneficial effects: 1) Accurate control of the reactive power output of the system under grid asymmetrical fault conditions, ensuring the output meets the grid requirements for injecting positive and negative sequence reactive currents and realizing full-process grid-forming control; 2) On the basis of fully considering the capacity of the grid-forming grid-connected inverter, setting the active current of the system to 0 can effectively suppress fault currents during faults and improve the stability margin of the system.