LAUSR

In order to deal with the stability issues in power systems, small-signal impedance models of three-phase voltage-source converters (VSCs) have been well established and widely studied viewing from the ac side. However, with the rapid development of renewable energy sources, the interactions between converters and dc networks need to be further formulated. Hence, dc-side impedance models of three-phase VSCs should be built and examined. In this article, three-phase VSCs are modeled from dc perspective, and several typical control methods are considered, respectively. By using the proposed models, impedance stability analyses are presented. It is shown that the dc-side output impedance has a great influence on the system stability, and the impedance mismatching between dc networks and VSCs can lead to system oscillation. In addition, the influence of controller parameters on the dc-side impedance is disclosed by simulation. Finally, the aforementioned analyses are verified by hardware-in-loop (HIL) tests.