Closed-Loop Interconnected Model of Multi-Inverter-Paralleled System and its Application to Impact Assessment of Interactions on Damping Characteristics

The influence of parameters on the damping characteristics in a multi-inverter-paralleled system is different from that in a single-inverter system, because of inverter interactions in a nonideal grid. To quantify the interaction degree and assess its impact on damping characteristics, this paper proposes a closed-loop interconnected model for multi-inverter-paralleled systems. The model can explain the impact mechanism of inverter interactions on system stability. Capacity expansion of inverter-based renewable distributed generation is taken as the background in this paper, and then, the proposed model is applied to assessing the influence of the collecting line length of the newly installed inverters on the overall system stability. The conclusion is that the damping of a multi-paralleled-inverter system in the medium frequency range degrades with the approaching of the lengths of the newly added line and the existing line. Therefore, to avoid damping degradation in capacity expansion scenarios, the length of the newly added line should be different from the length of existing lines or the parameters of new inverters should be readjusted. Simulation results are presented to verify the effectiveness of the proposed model and stability enhancement approaches.