Experimental Study of the Impacts on 2-9 kHz Harmonics due to IBRs connected to a Distribution Line

This study experimentally investigates harmonic voltage distortion in the 2-9 kHz range caused by series resonance between IBRs and the grid, and explains the underlying mechanism.

Moreover, the changes in this phenomenon when multiple IBRs are installed at different locations are experimentally considered. The results reveal that when two inverters are connected and operated simultaneously, the high-order harmonic voltage distortion observed at the grid-side capacitor is significantly influenced by variations in the switching frequency of the inverter, located closer to the grid. In contrast, changes in the switching frequency of the terminal-side inverter have a relatively small impact on the voltage distortion. Impedance measurements at the inverter connection points show that the impedance characteristics observed from the grid-side inverter terminal are only slightly affected by the connection status of the other inverter. However, the impedance characteristics observed from the terminal-side inverter terminal are significantly influenced by the connection status of the other inverter.

Consequently, when both inverters are connected, the influence of the terminal-side inverter’s switching frequency on the grid-side high-order harmonic voltage distortion is reduced, and the distortion becomes dominated by the series resonance characteristics at the grid-side inverter connection point. These results experimentally confirm that the 2-9 kHz harmonic voltage distortion phenomenon varies depending on the inverter connection status. Therefore, when evaluating the impact of IBR integration on 2-9 kHz harmonics, it is necessary to consider not only grid impedance and inverter switching frequency, but also the inverter connection status.