Understanding of Power Oscillation Mechanism Analysis with Fluctuation Propagation in Grid-Forming Converter

This work proposes a generic model for clarifying the mechanism hidden in the phenomena of fluctuation propagation in grid-forming (GF-VSG) systems, considering the impact of different disturbances. Additionally, a new judgment criterion is established to give physical insights into the power oscillation stability of the GFMC system. And this judgment criterion, as well as the model, can identify the power stability combined with fluctuation propagation phenomenon no matter what the disturbance is, which can also give guidance to the controller design to guarantee that the GFMC can operate in normal operation conditions while leisurely confronting various disturbances. In addition, it is found that the established conventional single closed-loop system may lose effectiveness in judging stability, especially when the oscillation propagation of disturbance occurs. Finally, the proposed model and judgment criteria are demonstrated by experiments.