Carrier Phase-Shift PWM to Reduce Common-Mode Voltage for Three-Level T-Type NPC Inverters

Tuyen D. Nguyen,Dzung Quoc Phan,Dat Ngoc Dao,Hong-Hee Lee 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.6

Common-mode voltage (CMV) causes overvoltage stress to winding insulation and damages AC motors. CMV with high dv/dt causes leakage currents, which create noise problems for equipment installed near the converter. This study proposes a new pulse-width modulation (PWM) strategy for three-level T-type NPC inverters. This strategy substantially eliminates CMV. The principle for selecting suitable triangle carrier signals for the three-level T-type NPC is described. The proposed method can mitigate the peak value of CMV by 50% compared with the phase disposition pulse-width modulation method. Furthermore, the proposed method exhibits better harmonic spectrum and lower root mean square value for the CMV than those of the reduced-CMV method on the basis of the phase opposition disposition PWM scheme with modulation index higher than 0.5. The proposed modulation can easily be implemented using software without any additional hardware modifications. Both simulation and experimental results demonstrate that the proposed carrier phase-shift PWM method has good output waveform performance and reduces CMV.

Subsequence Action to Eliminate Blackout after Detecting Islanding using Solid State Transfer Switch Implemented in PSCAD/EMTDC

Tuyen, Nguyen Duc,Fujita, Goro,Funabashi, Toshihisa,Nomura, Masakatsu The Korean Institute of Electrical Engineers 2012 The Journal of International Council on Electrical Vol.2 No.1

One operation circumstance in Dispersed Generation (DG) concepts, an island, is formed when one or more DGs and an aggregate of local loads are disconnected from the main grid and then, remain operational as an islanded entity. This condition of islanding is conventionally undesirable. Consequently, the customers will suffer the blackout. Recently, this blackout phenomenon has been eliminating by facilitating islanded operation. This paper presents a passive method in detecting islanding for DGs by measuring the negative-sequence impedance differences between islanded mode and grid-connected mode at the line frequency. Subsequently, the islanded entity is connected to a backup system by Solid State Transfer Switch (SSTS) in order to smoothly and quickly keep electricity available to customers.

Mathematical models applied to dispersal data of pest populations in greenhouse

Tuyen Van Nguyen,Chunlei Xia,Bu-Keun Chung,Hwang-Yong Kim,Tae-Soo Chon 한국응용곤충학회 2011 한국응용곤충학회 학술대회논문집 Vol.2011 No.05

In order to achieve the optimized pest control, correct estimation of pest densities is a prerequisite to monitor pest damage and to provide efficient pest management plans. Parameters regarding diffusion (e.g., diffusion constant) and population size (e.g., growth rate) were estimated by using diffusion equation. The time series dispersal data of Whiteflies collected in greenhouse were used for modeling. Cross-correlation analysis was conducted to reveal the range and direction of pest population invasion. Sampling theory was further investigated regarding estimation of densities, and population dynamics of Whiteflies were discussed in two dimensions.

Modeling applied to drifting in aquatic insects

Tuyen Van Nguyen,Rupert Mazzucco,Dong-Hwan Kim,Ulf Dieckmann,Tae-Soo Chon 한국응용곤충학회 2011 한국응용곤충학회 학술대회논문집 Vol.2011 No.05

Stream and river habitats are characterized by a uni-directional water flow. Organisms colonizing such habitats are faced with the constraint of continuous downstream flow. Some ecologists find it puzzling that upstream is colonized by insect communities although the insects are continuously faced with downstream flow. The obvious solution to the puzzle is that there exist compensatory strategies, three of which have gained some notoriety in recent years: 1) diffusive random movement and density-dependent regulation of population size; 2) daily directed movement during larvae stage; 3) the compensation of larval drift by adult upstream flight. We have adapted an eco-evolutionary individual-based model (IBM) to accommodate typical life events of aquatic insects, such as birth, death, diffusion, and drifting. The probabilities of these events, which occur on the individual level, depend on both biological (e.g., local competition, upstream flight by adult insects) and environmental (e.g., unidirectional flow) constraints. The evolution of selected traits, namely, adapted water velocity, drifting time and distance, and upward flight distance, was investigated through simulation. We find that, while the three strategies are generally able to sustain upstream populations, the exact compensation of drift loss allowed by upstream flight makes the third strategy less “asteful” a population of upstream flight strategists to outcompete diffusive movement strategists. We also report branching of adapted traits in drifting during the course of evolution. Individuals with high current velocity preferences either spend short (several seconds) or long (an hour) duration in water flow, while the individuals with low current-velocity preference only spend middle range (half an hour) of duration in water flow.

Univector field method-based multi-agent navigation for pursuit problem in obstacle environments

Tuyen, L. P.,Viet, H. H.,An, S. H.,Lee, S. G.,Kim, D. H.,Chung, T. C. Springer Science + Business Media 2017 Journal of Central South University Vol.24 No.4

Nitrogen removal performance of anammox process with PVA–SA gel bead crosslinked with sodium sulfate as a biomass carrier

Tuyen, N.V.,Ryu, J.H.,Yae, J.B.,Kim, H.G.,Hong, S.W.,Ahn, D.H. Elsevier 2018 Journal of industrial and engineering chemistry Vol.67 No.-

<P><B>Abstract</B></P> <P>In this study, the result shows that polyvinyl alcohol–sodium alginate (PVA–SA) gel bead crosslinked with sodium sulfate are better among the different methods by comparing the relative mechanical strength, mechanical strength swelling and expansion coefficient of beads in water. Subsequently, anammox biomass entrapment by PVA–SA gel was introduced into continuous stirred tank reactor (CSTR). After 24 operation days, the nitrogen removal efficiency achieved 60%, while the nitrogen loading rate (NLR) was 0.14kgN/m<SUP>3</SUP>/d and the experiment data indicated that PVA–SA gel bead crosslinked with sodium sulfate can be used to initiate anammox process. Furthermore, it is an alternative for culturing anammox in a long-term operation.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Carrier-based PWM Method for Four-Leg Very Sparse Matrix Converter

Tuyen D. Nguyen,Hong-Hee Lee 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

The matrix converters are a good alternative to back-to-back converter in variable speed AC generation to supply energy to a stand-alone load or grid. In case of the unbalanced load, the four-leg matrix converter is required because this topology can effectively provide a path of neutral current. In this paper, a carrier-based PWM modulation is proposed to control the four-leg very sparse matrix converter. The proposed method has less computation complexity for digital signal processor. The algorithm uses only one carrier signal to generate PWMs for both rectifier stage and inverter stage control. The simulation and experimental results are provided to validate the feasibility of the proposed method.

Synthesis and Antiinflammatory Activity of 1,5-Diarylimidazoles

Tuyen Truong Ngoc,Sin Kwang-Seog,Kim Hyun Pyo,Park Haeil The Pharmaceutical Society of Korea 2005 Archives of Pharmacal Research Vol.28 No.9

A number of 1,5-diarylimidazoles has been synthesized and evaluated for their inhibitory activities of COX-2 catalyzed $PGE_2$ production. 1,5-Diarylimidazoles were obtained from imimes and p-toluenesulfonylmethyl cyanide (TosMIC). Imines were prepared from commercially available amines and aldehydes. Among the compounds tested, 1-(2,4-difluorophenyl)-5-(4­methylsulfonylphenyl)imidazole (2r) showed strong inhibitory activity, however, most diarylimidazoles exhibited little to low inhibitory activities against COX-2 catalyzed $PGE_2$ production.

Effects of pretreatment and air drying temperature on Noni fruit powder

Tuyen Chan Kha,Cong Thanh Nguyen,Luyen Thi Tran,Trung Tan Truong 한국식품과학회 2021 Food Science and Biotechnology Vol.30 No.12

The plant Morinda citrifolia L. (Noni) has beenthe subject of several recent research due to its positiveimpact on the treatment and prevention of a variety ofdiseases. Noni fruits contain a variety of phytochemicals,including flavonoid, polyphenol, and triterpenoid saponin. This study aimed to determine the best pre-treatment (includingblanching, soaking in ascorbic acid solution andmetabisulfite solution) and air-drying temperature (50, 60,70, and 80 C) to maximize the total polyphenol content(TPC), flavonoid content (TFC), and triterpenoid saponincontents (TSC) of the resultant Noni fruit powder. Theresults revealed that pre-soaked Noni fruit samples inascorbic acid or metabisulfite solution before air-drying at60 C were beneficial in preserving TPC, TFC, and TSC. TPC, TFC, and TSC losses increased as drying temperatures(70 and 80 C) rose. The optimum sample was held atfive different relative humidity conditions until theyattained weight equilibrium. The results indicated that thesorption isotherm curve of the Noni powder was the sigmoidshape and fitted with the BET and GAB models.

A New Comprehensive Short-form Health Literacy Survey Tool for Patients in General

Tuyen Van Duong,Peter WuShou Chang,Shih-Hsien Yang,Ming-Chu Chen,Wei-Ting Chao,Tara Chen,Priscilla Chiao,Hsiao-Ling Huang 한국간호과학회 2017 Asian Nursing Research Vol.11 No.1

Purpose: To validate a conceptual short-form health literacy 12 items questionnaire (HL-SF12) in patient populations. Methods: A cross-sectional study was conducted via a convenient sample of 403 patients from three departments of a community general hospital in the northern Taiwan. Patients’ health literacy was assessed with a validated HL-SF12, derived from the full scale, the European Health Literacy Survey Questionnaire (HLS-EU-Q), as well as a single-item from Chew’s Set of Brief Health Literacy Question. A reference population in Northern Taiwan (n = 928) via the HLS-EU-Q in 2013e2014 was used as a reference to compare the health literacy between that of the general public and the patients. Data was analyzed by confirmatory factor analysis (CFA), internal consistency analysis, correlation analysis, and linear regression models. Results: Patients’ health literacy assessed with the HL-SF12 was shown with high internal consistency (Cronbach a = .87), and moderately correlated with the single-item from Chew's Set of Brief Health Literacy Question, with satisfactory item-scale convergent validity (item-scale correlation> .40), without floor/ceiling effect, and with satisfactory goodness of fit indices of the three-factor construct model for most of the patients. Their health literacy was significantly positively associated with female gender, higher income, and more often watching health-related TV programs. On the other hands, patients were reported with significantly higher healthcare health literacy than the general public, but not in general health literacy, disease prevention health literacy, or health promotion health literacy. Conclusion: The comprehensive HL-SF12 was a valid and easy to use tool for assessing patients’ health literacy in the hospitals to facilitate healthcare providers in enhancing patients’ health literacy and healthcare qualities.