Influence of Virtual Synchronous Generators on Low Frequency Oscillations

By simulating the operating dynamics of synchronous generators(SGs),the use of virtual synchronous gen-rators(VSGs)can help overcome inverter-based generators'shortcomings of low inertia and minimal damping for gridforming applications.VSGs'stability are very important for their solar and wind electricity applications.Currently,the related research primarily focuses on VSGs and their applications for microgrids.There has been little research to explore how VSGs effect low frequency oscillations in power transmission systems.This paper describes a small-signal model of a VSGSG interconnected system,which is suitable for studying low frequency oscillation damping in a power transmission grid.Based on this model,the effects of VSGs on low frequency oscillations are compared with the effects of SGs to reveal the mechanism of how VSGs infuence damping characteristics.The influence of each VSG control loop on oscillations is also analyzed in this paper.Then,the low frequency oscillation risks with different types of VSGs are described.Finally,experiments on a real-time laboratory(RT-LAB)platform are conducted to verify the small-signal analysis results.

The phytolith carbon sequestration in terrestrial ecosystems:the underestimated potential of bamboo forest

Background Terrestrial ecosystems contain significant carbon storage,vital to the global carbon cycle and climate change.Alterations in human production activities and environmental factors affect the stability of carbon storage in soil.Carbon sequestration in plant phytoliths offers a sustainable method for long-term carbon stabilization.Carbon occluded in phytoliths(PhytOC)is a kind of carbon that can be stable and not decomposed for a long time,so it is crucial to conduct more in-depth research on it.Results We undertook a meta-analysis on PhytOC across global terrestrial ecosystems,analyzing 60 articles,encapsulating 534 observations.We observed notable differences in phytolith and PhytOC contents across various ecosystems.Bamboo forest ecosystems exhibited the highest vegetation phytolith and PhytOC content,while soil phytolith content was most prominent in bamboo forests and PhytOC content in croplands.Human activities,such as grassland grazing,had a lesser impact on soil PhytOC transport than actions like cutting and tillage in croplands and forests.Our study separated bamboo ecosystems,analyzing their PhytOC content and revealing an underestimation of their carbon sink capacity.Conclusions Notwithstanding our findings,phytoliths’intricate environmental interactions warrant further exploration,crucial for refining ecosystem management and accurately estimating PhytOC stocks.This deepened understanding lays the foundation for studying phytoliths and the carbon sink dynamics.