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- 저자 : Dean Zhao (검색결과 3 건)
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Grid-Connected Dual Stator-Winding Induction Generator Wind Power System for Wide Wind Speed Ranges
Shi, Kai,Xu, Peifeng,Wan, Zengqiang,Bu, Feifei,Fang, Zhiming,Liu, Rongke,Zhao, Dean The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.4
This paper presents a grid-connected dual stator-winding induction generator (DWIG) wind power system suitable for wide wind speed ranges. The parallel connection via a unidirectional diode between dc buses of both stator-winding sides is employed in this DWIG system, which can output a high dc voltage over wide wind speed ranges. Grid-connected inverters (GCIs) do not require booster converters; hence, the efficiency of wind energy utilization increases, and the hardware topology and control strategy of GCIs are simplified. In view of the particularities of the parallel topology and the adopted generator control strategy, we propose a novel excitation-capacitor optimization solution to reduce the volume and weight of the static excitation controller. When this excitation-capacitor optimization is carried out, the maximum power tracking problem is also considered. All the problems are resolved with the combined control of the DWIG and GCI. Experimental results on the platform of a 37 kW/600 V prototype show that the proposed DWIG wind power system can output a constant dc voltage over wide rotor speed ranges for grid-connected operations and that the proposed excitation optimization scheme is effective.
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Connecting Dopant Bond Type with Electronic Structure in N-Doped Graphene
Schiros, Theanne,Nordlund, Dennis,Pá,lová,, Lucia,Prezzi, Deborah,Zhao, Liuyan,Kim, Keun Soo,Wurstbauer, Ulrich,Gutié,rrez, Christopher,Delongchamp, Dean,Jaye, Cherno,Fischer, Daniel American Chemical Society 2012 Nano letters Vol.12 No.8
<P>Robust methods to tune the unique electronic properties of graphene by chemical modification are in great demand due to the potential of the two dimensional material to impact a range of device applications. Here we show that carbon and nitrogen core-level resonant X-ray spectroscopy is a sensitive probe of chemical bonding and electronic structure of chemical dopants introduced in single-sheet graphene films. In conjunction with density functional theory based calculations, we are able to obtain a detailed picture of bond types and electronic structure in graphene doped with nitrogen at the sub-percent level. We show that different N-bond types, including graphitic, pyridinic, and nitrilic, can exist in a single, dilutely N-doped graphene sheet. We show that these various bond types have profoundly different effects on the carrier concentration, indicating that control over the dopant bond type is a crucial requirement in advancing graphene electronics.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2012/nalefd.2012.12.issue-8/nl301409h/production/images/medium/nl-2012-01409h_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl301409h'>ACS Electronic Supporting Info</A></P>
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Grid-Connected Dual Stator-Winding Induction Generator Wind Power System for Wide Wind Speed Ranges
Kai Shi,Peifeng Xu,Zengqiang Wan,Feifei Bu,Zhiming Fang,Rongke Liu,Dean Zhao 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.4
This paper presents a grid-connected dual stator-winding induction generator (DWIG) wind power system suitable for wide wind speed ranges. The parallel connection via a unidirectional diode between dc buses of both stator-winding sides is employed in this DWIG system, which can output a high dc voltage over wide wind speed ranges. Grid-connected inverters (GCIs) do not require booster converters; hence, the efficiency of wind energy utilization increases, and the hardware topology and control strategy of GCIs are simplified. In view of the particularities of the parallel topology and the adopted generator control strategy, we propose a novel excitation–capacitor optimization solution to reduce the volume and weight of the static excitation controller. When this excitation–capacitor optimization is carried out, the maximum power tracking problem is also considered. All the problems are resolved with the combined control of the DWIG and GCI. Experimental results on the platform of a 37 kW/600 V prototype show that the proposed DWIG wind power system can output a constant dc voltage over wide rotor speed ranges for grid-connected operations and that the proposed excitation optimization scheme is effective.
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