Line Impedance Estimation Based Adaptive Droop Control Method for Parallel Inverters

Le, Phuong Minh,Pham, Xuan Hoa Thi,Nguyen, Huy Minh,Hoang, Duc Duy Vo,Nguyen, Tuyen Dinh,Vo, Dieu Ngoc The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

This paper presents a new load sharing control for use between paralleled three-phase inverters in an islanded microgrid based on the online line impedance estimation by the use of a Kalman filter. In this study, the mismatch of power sharing when the line impedance changes due to temperature, frequency, significant differences in line parameters and the requirements of the Plug-and-Play mode for inverters connected to a microgrid has been solved. In addition, this paper also presents a new droop control method working with the line impedance that is different from the traditional droop algorithm when the line impedance is assumed to be pure resistance or pure inductance. In this paper, the line impedance estimation for parallel inverters uses the minimum square method combined with a Kalman filter. In addition, the secondary control loops are designed to restore the voltage amplitude and frequency of a microgrid by using a combined nominal value SOGI-PLL with a generalized integral block and phase lock loop to monitor the exact voltage magnitude and frequency phase at the PCC. A control model has been simulated in Matlab/Simulink with three voltage source inverters connected in parallel for different ratios of power sharing. The simulation results demonstrate the accuracy of the proposed control method.

What Influences Decision on Seasoned Equity Offerings of Listed Vietnamese Companies?

LE, Long Hau,NGUYEN, Thi Binh Nhi,PHAM, Xuan Quynh,VUONG, Quoc Duy,LE, Tan Nghiem Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.5

This paper investigates the determinants on decision to conduct seasoned equity offerings (SEOs) of listed companies on the Ho Chi Minh Stock Exchange in Vietnam. Seasoned equity offerings (SEOs) are defined as the issue of more stocks by a firm to raise more capital after a primary issue. Using panel data collected from audited financial statements of 99 listed companies on the Ho Chi Minh Stock Exchange during 2014-2018, the study employs a logit regression model by fixed effects method to examine factors that affect the decision to implement seasoned equity offerings of those companies. The findings of this study show that profit, revenue growth and company's size have a positively significant impact on the decision, while dividend pay-out ratio negatively significantly influences the equity issuing decision. Furthermore, these results are robust after controlling for the forms of equity offerings, i.e. bonus stocks, stock dividends and rights to buy shares. These findings are consistent with economic theories such as agency theory, pecking order theory, and growth opportunity theory, and also could be explained by the real situations of the Vietnamese stock exchange. This study has important implications for corporate managers, policy makers and investors.

The Impact of Corporate Social Responsibility on Brand Image: A Case Study in Vietnam

Cuong Xuan PHAN,Lam Van LE,Duy DUONG,Thuy Chung PHAN 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.4

This paper examines the impact of university social responsibility on brand image and student satisfaction. Social responsibility impact on consumer behavior has been studied extensively. But the same impact has not been rigorously tested to the same extend in the education sector. Firstly, we analyze the perception of university social responsibility (USR) and its components, including (1) the quality of teaching programs, facilities, and academic staff; (2) supporting learning activities; and (3) human resource policies. Secondly, we investigate the relationship between university social responsibility, brand image, and student satisfaction. The study examined these relationships through a proposed economic model based on answers from a survey of 298 students at the University of Food Industry Ho Chi Minh City. From the above survey data, the author proceeds to quantify variables and, based on Cronbach’s Alpha reliability coefficient, EFA factor analysis, and linear regression, to measure the impact of each social responsibility factor on business of the university and student satisfaction. The results show that university social responsibility actually affects the university’s brand image and student satisfaction. Our findings suggest that universities should develop an appropriate marketing strategy to reinforce brand image and student satisfaction through the university social responsibility model.

Line Impedance Estimation Based Adaptive Droop Control Method for Parallel Inverters

Phuong Minh Le,Xuan Hoa Thi Pham,Huy Minh Nguyen,Duc Duy Vo Hoang,Tuyen Dinh Nguyen,Dieu Ngoc Vo 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

This paper presents a new load sharing control for use between paralleled three-phase inverters in an islanded microgrid based on the online line impedance estimation by the use of a Kalman filter. In this study, the mismatch of power sharing when the line impedance changes due to temperature, frequency, significant differences in line parameters and the requirements of the Plug-and-Play mode for inverters connected to a microgrid has been solved. In addition, this paper also presents a new droop control method working with the line impedance that is different from the traditional droop algorithm when the line impedance is assumed to be pure resistance or pure inductance. In this paper, the line impedance estimation for parallel inverters uses the minimum square method combined with a Kalman filter. In addition, the secondary control loops are designed to restore the voltage amplitude and frequency of a microgrid by using a combined nominal value SOGI-PLL with a generalized integral block and phase lock loop to monitor the exact voltage magnitude and frequency phase at the PCC. A control model has been simulated in Matlab/Simulink with three voltage source inverters connected in parallel for different ratios of power sharing. The simulation results demonstrate the accuracy of the proposed control method.

Ginsenosides from Korean red ginseng modulate T cell function via the regulation of NF-AT-mediated IL-2 production

LEBAVINH,박정업,Le Xuan Duy,Nguyen Thi Minh Nguyet,양서영,김영란,김영호 한국식품과학회 2019 Food Science and Biotechnology Vol.28 No.1

Korean red ginseng is a traditional health foodfrequently used to prevent or treat various diseasesworldwide. In this study, we evaluated the immunomodulatoryactivities of eleven compounds (1–11) isolated fromKorean red ginseng, focusing on T cell function. First, theeffects of the eleven compounds were studied on the regulationof IL-2, a potent T cell growth factor. Compounds5, 7, and 9 significantly increased IL-2 secretion in phorbol12-myristate 13-acetate (PMA)/ionomycin (Io)-inducedEL-4 T cells. Next, we examined the effects of compounds5, 7, and 9 on the regulation of transcription factors relatedto IL-2 production in T cells. Compound 9 significantlyincreased the PMA/Io-induced promoter activity of nuclearfactor of activated T cells (NF-AT) in EL-4 T cells, but didnot have any significant effects on the promoters of NFjB. These results suggest that compound 9 activates T cellfunction via the regulation of NF-AT-mediated IL-2production.

Cellobiose dehydrogenase from the agaricomycete Coprinellus aureogranulatus and its application for the synergistic conversion of rice straw

Nghi Do Huu,Kellner Harald,Büttner Enrico,Huong Le Mai,Duy Le Xuan,Giap Vu Dinh,Quynh Dang Thu,Hang Tran Thi Nhu,Verberckmoes An,Diels Ludo,Liers Christiane,Hofrichter Martin 한국응용생명화학회 2021 Applied Biological Chemistry (Appl Biol Chem) Vol.64 No.5

From the biotechnological viewpoint, the enzymatic disintegration of plant lignocellulosic biomass is a promising goal since it would deliver fermentable sugars for the chemical sector. Cellobiose dehydrogenase (CDH) is a vital component of the extracellular lignocellulose-degrading enzyme system of fungi and has a great potential to improve catalyst efficiency for biomass processing. In the present study, a CDH from a newly isolated strain of the agaricomycete Coprinellus aureogranulatus (CauCDH) was successfully purified with a specific activity of 28.9 U mg− 1. This pure enzyme (MW = 109 kDa, pI = 5.4) displayed the high oxidative activity towards β-1–4-linked oligosaccharides. Not least, CauCDH was used for the enzymatic degradation of rice straw without chemical pretreatment. As main metabolites, glucose (up to 165.18 ± 3.19 mg g− 1), xylose (64.21 ± 1.22 mg g− 1), and gluconic acid (5.17 ± 0.13 mg g− 1) could be identified during the synergistic conversion of this raw material with the fungal hydrolases (e.g., esterase, cellulase, and xylanase) and further optimization by using an RSM statistical approach.

Preliminary study of doxycycline adsorption from aqueous solution on alkaline modified biochar derived from banana peel

Van-Truc Nguyen,Thanh-Binh Nguyen,Thi-Dieu-Hien Vo,Nguyen Duy Dat,Thi-Kim Quyen Vo,Xuan Cuong Nguyen,Viet-Cuong Dinh,Thi-Ngoc-Chau Le,Thi-Giang-Huong Duong,Manh-Ha Bui,Xuan-Thanh Bui 대한환경공학회 2023 Environmental Engineering Research Vol.29 No.3

This study explores the adsorption of doxycycline (DOX) from aqueous solutions onto biochar derived from banana peel, which was prepared using a potassium hydroxide activation method (KOH-BPB). The biochar properties were characterized based on morphology, surface area (SBET of 710.241 ㎡ g<SUP>−1</SUP>), functional groups, and surface charge (pHPZC = 7.7). Parameters, including initial pH, DOX concentration, and ionic strength, that influenced the DOX adsorption capacity of KOH-BPB were examined. Adsorption equilibrium of DOX on KOH-BPB was assessed through four isothermal models: the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models. The obtained data were most compatible with the Langmuir model (R² = 0.9879). KOH-BPB has a maximum DOX absorption capacity of 121.95 mg g<SUP>-1</SUP> which exceeds that of many comparable absorbents. The maximum DOX removal was 96.7% at pH 6, a DOX concentration of 20 mg L<SUP>-1</SUP>, and a KOH-BPB dose of 1.0g L<SUP>-1</SUP>. These findings reveal that biochar from banana peel effectively removes antibiotic residues from water. This study provides a potential, low-cost, and environmentally friendly adsorbent.