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Yuan Zeng,Yang Yang,Chao Qin,Jiangtao Chang,Jian Zhang,Jingzhe Tu 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.1
The dynamic characteristics of power systems become more and more complex because of the integration of large-scale wind power, which needs appropriate control strategy to guarantee stable operation. With wide area measurement system(WAMS) creating conditions for realizing realtime transient stability analysis, a new coordinated control strategy for power system transient stability control based on phase-plane trajectory was proposed. When the outputs of the wind farms change, the proposed control method is capable of selecting optimal generators to balance the deviation of wind power and prevent transient instability. With small disturbance on the base operating point, the coordinated sensitivity of each synchronous generator is obtained. Then the priority matrix can be formed by sorting the coordinated sensitivity in ascending order. Based on the real-time output change of wind farm, coordinated generators can be selected to accomplish the coordinated control with wind farms. The results in New England 10-genrator 39-bus system validate the effectiveness and superiority of the proposed coordinated control strategy.
Xu Jiangtao,Feng Yong,Chang Siqin,Guo Tongjun 한국자동차공학회 2020 International journal of automotive technology Vol.21 No.6
As one of the most common engine types in nowadays, the thermal efficiency of spark-Ignition (SI) engine is limited due to the lower compression ratio. Various technical solutions have been proposed to suppress knock and improve compression ratio of SI engines. In this paper, an new technical solution based on electromagnetic valve train (EMVT) was proposed to suppress knock of spark ignition engines, so that high compression ratio (HCR) engine (13:5) was obtained. Moreover, experimental and numerical analyses were carried out to optimize the proposed EMVT strategy. The result showed that the proposed EMVT strategies could well suppress the engine knock by reducing end-gas temperature and pressure and improving the spark-flame rate, resulting in significantly enhanced power, economic, and emission characteristics of SI engines. This study provides theoretical basis and technical approach for the development of internal combustion engines with high efficiency and high compression ratio.
ULTRA-NARROW NEGATIVE FLARE FRONT OBSERVED IN HELIUM-10830 Å USING THE 1.6 m NEW SOLAR TELESCOPE
Xu, Yan,Cao, Wenda,Ding, Mingde,Kleint, Lucia,Su, Jiangtao,Liu, Chang,Ji, Haisheng,Chae, Jongchul,Jing, Ju,Cho, Kyuhyoun,Cho, Kyungsuk,Gary, Dale,Wang, Haimin American Astronomical Society 2016 The Astrophysical journal Vol.819 No.2
<P>Solar flares are sudden flashes of brightness on the Sun and are often associated with coronal mass ejections and solar energetic particles that have adverse effects on the near-Earth environment. By definition, flares are usually referred to as bright features resulting from excess emission. Using the newly commissioned 1.6. m New Solar Telescope at Big Bear Solar Observatory, we show a striking 'negative' flare with a narrow but unambiguous 'dark' moving front observed in He I 10830 angstrom, which is as narrow as 340 km and is associated with distinct spectral characteristics in Ha and Mg II lines. Theoretically, such negative contrast in He I 10830 angstrom can be produced under special circumstances by nonthermal electron collisions or photoionization followed by recombination. Our discovery, made possible due to unprecedented spatial resolution, confirms the presence of the required plasma conditions and provides unique information in understanding the energy release and radiative transfer in astronomical objects.</P>