Output Response Characteristics of Multiple Parallel Inverters under Weak Grid Conditions

Under weak grid conditions, the grid impedance causes the point of common coupling (PCC) voltage to become non-constant. As a result, the output current of the inverter is influenced by grid voltage fluctuation while simultaneously affecting the PCC voltage. In order to quantitatively analyze the output response characteristics and interaction mechanism of multiple parallel inverter nodes, this paper investigates the L-type three-phase grid-connected inverter based on the vector control strategy of grid-voltage-oriented and the dual-loop control strategy of voltage and current. By analyzing the system model and dynamic equations of the grid-connected inverter, the transfer function of the single-inverter closed-loop system is derived. The interaction mechanism of multiple parallel grid-connected inverters is analyzed based on the transfer function of a single-inverter system. Finally, the three-phase grid-connected inverter model was developed in Matlab/Simulink. The effectiveness of the derived transfer function and interaction mechanism was verified through a case study, and the output response characteristics of the multi-parallel inverter nodes were quantitatively analyzed.