• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.6
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• pp.540-549
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• 2015

Unintentional islanding results in safety hazards, reliability, and many other issues. Therefore, the islanding detection of a power conditioning system of a distributed generation, such as a grid-connected photovoltaic inverter, is a key function for standard compliance. Currently, many anti-islanding schemes have been examined, but existing anti-islanding schemes have poor power quality and non-detection zone issues. Therefore, this study analyzes the non-detection zone in a more deliberate manner than the existing analysis of the non-detection zone and proposes a new anti-islanding scheme, which has negligible power quality degradation and no non-detection zone. Simulation and experimental results validate that the proposed scheme shows much better performance than other existing schemes.

• Journal of Power Electronics
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• v.10 no.6
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• pp.762-768
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• 2010

This paper describes the development of a new islanding detection method for inverter-based distributed generation systems, which uses a signal cross-correlation scheme between the injected reactive current and the power frequency deviation. The proposed method injects 1% of the reactive current to the rated current which brings about a negligible degradation of the power quality. It discriminates the islanding state, when the calculated cross-correlation index is larger than 0.5. The operational feasibility was verified through computer simulations with PSCAD/EMTDC software and experimental research with a hardware prototype. The proposed method can detect the islanding state without degrading the power quality at the point of common connection. Further study is required to overcome the cancellation of the injected reactive current from multiple distributed generation units interconnected with the utility grid.

• Korean Journal of Pharmacognosy
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• v.48 no.1
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• pp.70-76
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• 2017

Dendranthema spp are distributed in various regions in Korea. This report is the quantitative results of phenolic compounds on the 5 resources collected from all over the country. It was known that it has phenolic compounds, as an anticoagulant activities and immunoadjuvant activity of contribute to the cardiovascular effects. This was used for quantitative analysis of chlorogenic acid(CA), 3,5-Dicaffeoylquinic acid(3,5-DCA), 4,5-Dicaffeoylquinic acid(4,5-DCA) and linarin, with UPLC-PDA and LC-IT-TOF-MS. Extraction efficiency of compounds was compared by using ultrasonic extraction and reflux extraction with different extraction conditions (methods and time). In 50% MeOH extracs (30 mins) of Dendranthema zawadskii (Herb.) Tzvelev (SDZ), Dendranthema zawadskii var. yezoense (Maek.) Y.M.Lee & H.J.Choi (NDZ), Dendranthema zawadskii (Herb.) Tzvelev var. teuisectum (Kitag.) J. H. Pak (GDZ), Dendranthema careanum (H. $L{\acute{e}}v$. & Vaniot) Vorosch. (HDC) and Dendranthema zawadskii var. tenuisectum Kitag (PDZ), chlorogenic acid contents were 1.14‰, 6.95‰, 7.27‰, 1.47‰ and 2.64‰, 3,5-dicaffeoylquinic acid contents were 3.30‰, 5.60‰, 10.81‰, 2.67‰ and 1.50‰, 4,5-dicaffeoylquinic acid contents were 0.74‰, 1.93‰, 3.36‰, 0.61‰ and 0.43‰ and linarin contents were 3.90‰, 10.15‰, 0.15‰, 0.73‰ and 0.21‰, respectively.

• 전자공학회논문지 IE
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• v.43 no.2
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• pp.63-69
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• 2006

Islanding phenomenon of utility-connected PV power conditioning systems(PV PCS) can cause a variety of problems and must be prevented. If the real and reactive powers supplied by PV PCS are closely matched to those of load, islanding detection by passive methods becomes difficult. The active frequency drift(AFD) method, called the frequency bias method, enables islanding detection by forcing the frequency of the voltage in the islanding to drift up or down. In this paper, non-detection zone(NDZ) of AFD is analyzed for the islanding detection method of utility-connected PV PCS by simulation tool PSIM.