Abstract：The inherent control delay of the digital-control LCL grid-connected inverter would affect the control characteristic of the original resonance damping scheme, thereby decreasing the robustness of the system in weak grid. The multiple-input-multiple-output(MIMO) matrix of the multi-inverter parallel system based on different parameters is established firstly, and three criteria to ensure the stability of the system's grid current and interactive current is put forward. Furthermore, the influence of the digital-control-delay on the robustness of the system when the module adopts different switching frequencies is analyzed based on the frequency domain impedance method. Therefore, the introduction of a high-bandwidth inverter in the multi-inverter system is found to be effective in suppressing low-frequency resonance. Next, the interaction stability between the high-frequency module and the low-frequency module is analyzed, and the switching frequency of the high-bandwidth inverter is selected. Finally, a prototype of the high-bandwidth grid-connected inverter based on GaN was built. The effectiveness of the high-bandwidth inverter to improve the robustness of the system in weak grid is verified by experiment. This scheme provides a new idea for improving the stability of the distributed generation system.
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2022, Vol. 37 
