Browsing by Author "Mi, Zengqiang"

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    A Review of FACTS' Practical Consideration and Economic Evaluation
    (IEEE, 2009) Ren, H.; Watts Casimis, David; Mi, Z.; Lu, J.; Mi, Zengqiang; Lu, Jinling
    Flexible AC transmission systems (FACTS) and their controllers are of great interest today. FACTS controllers can offer great opportunities in modern power system, allowing better and safer operation of the grid. Their technical benefits are very well acknowledged, but there are some factors limiting the widespread of this technology: a) lack of a comprehensive consideration of FACTS for multiple operational problems and operational conditions, b) lack of economic assessment of FACTS projects for utilities and transmission entities [1] c) lack of a clear understanding of the options of devices and their configurations [1], and most importantly d) the high degree of uncertainty associated with the transmission system on the time scale that is needed to assess this kind of long-term projects. This paper gives a brief introduction of various FACTS devices and their controllers, main research methods. We mainly provide a survey of FACTS' economic assessment method proposed so far. We conclude that there is a huge literature body of technical benefits associated with FACTS targeting on single operational problems, but limited work on addressing their practical application considerations, and economic evaluation, offering great research opportunities.
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    Network motif as an indicator for cascading outages due to the decrease of connectivity
    (IEEE, 2017) Chen, Qunjie; Ren, Hui; Sun, Chenjung; Mi, Zengqiang; Watts Casimis, David Eduardo
    Complex network study pointed out that, between the macro level and the micro level, there still exist abundant various dimensions addressed as subgraph, including motifs, cliques, cores... The structural property of these subgraphs plays an import role for the robustness in the function of the system. In this paper, the network motif existing in different IEEE test systems and real power grids are identified, and the consistency between the structural feature of motif and power system design for reliable power supply is revealed. By incorporating the transmission line margin into the procedure of finding significant motifs, the risk of cascading overloads due to insufficient transmission capacity and the decrease of connectivity of the power network is reflected by the occurrence of certain motifs in the power network. Through the simulation of cascading failures along the continuous increase of load demand and random line failures, different phases in the evolution of cascading failures are defined, and the patterns in the occurrence of motifs corresponded to different phases are identified. The performance of network motifs as a warning signal for higher risk of large outages is also tested under continuous line/node removal scenario. Test results show that the occurrence of motifs can be a good supplement to the EENS to describe the risk of outages.