State of charge balancing for distributed batteries in DC microgrids without communication networks

Hoang, Khanh Duc,Lee, Hong-Hee The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.2

State of charge (SoC) balancing and accurate power sharing have been achieved among distributed batteries in a DC microgrid without a communication network by injecting an AC signal. The frequency of the generated signal is proportional to the SoC of a predefined master battery and it is used for the other batteries as a common variable to estimate the SoC and output power of the master battery. Based on modified droop control, the distributed batteries realize a balanced SoC and accurate power sharing regardless of the differences in the line resistance. A communication system is not required. Thus, the system cost is notably reduced. Moreover, to guarantee system reliability, a new master battery selection method is provided to replace the master battery under fault conditions. The effectiveness of the proposed strategy was verified by simulations and experimental results.

Universal Design Suggestions of Vietnam Subway Stations through Cases of South Korea

Hoang Khanh, Vo,이재용,조영행 대한건축학회지회연합회 2020 대한건축학회연합논문집 Vol.22 No.3

South Korea is one of countries with the most developed and efficient subway systems in the world. By applying Universal Design principles, the subway stations South Korea can be more functional and more user-friendly for everyone in South Korea. The purpose of this study is to evaluate subway stations facilities in South Korea by Universal Design principles to suggest subway stations design directions in Vietnam. Literature review, case study, and site-visits were used as study methods. The results showed that four subway lines in South Korea appeared high mobility, easy utilization and information. The best elements are found out through the evaluation of installation status of convenient facilities and application of Universal Design principles in subway stations. The best elements on six areas are as follows: Universal movement lines, Universal facilities, Universal walkways, Audio and visual information system, Universal signage, and identifiable stations. The conclusions are that the Universal Design applications of South Korea’s subway station designs are very well, South Korea cases for the experiences of Universal Design can be adaptable in Vietnam’s Subway station design. Therefore, Vietnam government policy for subway stations needs to reflect the Universal Design, and Universal Design principles should be considered in the beginning stage of the planning of the subway stations, and the communications for architects and managers are essential.

Accurate Power Sharing With Balanced Battery State of Charge in Distributed DC Microgrid

Hoang, Khanh Duc,Lee, Hong-Hee Institute of Electrical and Electronics Engineers 2019 IEEE transactions on industrial electronics Vol.66 No.3

<P>This paper presents an accurate power sharing method to balance the state of charge (SoC) among the distributed battery energy units (BEUs) in a dc microgrid. The virtual power rating concept of the proposed control method is introduced, and accurate power sharing is achieved according to the SoC levels and the virtual power ratings, regardless of the line resistance difference. With the accurate power sharing based on SoC, BEUs with higher SoC accurately supply more power to the system than the lower SoC BEUs during the discharging period, and BEUs with lower SoC accurately supply less power to the system than the higher SoC BEUs during the charging period. Moreover, with the voltage restoring method, the dc grid voltage is maintained within the desired voltage level, and with the proposed control method, the system stability is verified. The proposed control scheme is implemented in a distributed manner that relies on low bandwidth communication. The effectiveness of the proposed control method is proved by simulation and experiments.</P>

Comparative Analysis of Free Amino Acids in Human Milk in Four Asian Countries

Khanh Hong Thi HOANG,My Tuyen Thi NGUYEN,JaeHan KIM 한국생물공학회 2022 한국생물공학회 학술대회 Vol.2022 No.4

Economic Power Sharing to Minimize Generation Cost in a DC Microgrid

Khanh Duc Hoang,이홍희 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.2

This study developed an economic power-sharing method to minimize the total generation cost (TGC) in a DC microgrid based on an AC signal injection technique. Economic power sharing for each distributed generator (DG) is achieved by means of a small AC frequency without a communication network. The AC frequency is proportional to the DG’s incremental cost and is injected into the output voltage of the DG. The AC signal frequency is indirectly regulated to have economic power sharing with equivalent incremental cost for each DG, so the minimization of TGC is achieved instead of a straightforward optimization solution. Therefore, the control scheme is simple and easy to implement. The proposed power-sharing method overcomes the impact of diferences in line resistance and is realized in a decentralized manner without a communication network and with plug-and-play capability. The proposed control method was investigated theoretically and verifed experimentally.

State of Charge Balancing for Distributed Battery Units Based on Adaptive Virtual Power Rating in a DC Microgrid

Khanh Duc Hoang,이홍희 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.5

This paper proposes an adaptive virtual power rating method for state of charge (SoC) balancing among distributed battery units (BUs) in a DC microgrid. The virtual power rating is fl exibly determined according to the SoC to obtain the droop gain of BU, and the balanced SoC is achieved by means of the modifi ed droop controller. Because an accurate power sharing among BUs is satisfi ed by using only virtual power rating, SoC balancing performance is consistently ensured regardless of the line resistance diff erence. Moreover, the voltage restoration to keep the grid voltage at a desired value is easily realized without PI controller, and the proposed control strategy is implemented based on the distributed control method with simple low-bandwidth communication. The system stability is investigated, and the performance of the control method is demonstrated through both simulations and experiments.

Some characters of bacterial cellulases in goats' rumen elucidated by metagenomic DNA analysis and the role of fibronectin 3 module for endoglucanase function

Nguyen, Khanh Hoang Viet,Dao, Trong Khoa,Nguyen, Hong Duong,Nguyen, Khanh Hai,Nguyen, Thi Quy,Nguyen, Thuy Tien,Nguyen, Thi Mai Phuong,Truong, Nam Hai,Do, Thi Huyen Asian Australasian Association of Animal Productio 2021 Animal Bioscience Vol.34 No.5

Objective: Fibronectin 3 (FN3) and immunoglobulin like modules (Ig) are usually collocated beside modular cellulase catalytic domains. However, very few researches have investigated the role of these modules. In a previous study, we have sequenced and analyzed bacterial metagenomic DNA in Vietnamese goats' rumen and found that cellulase-producing bacteria and cellulase families were dominant. In this study, the properties of modular cellulases and the role of a FN3 in unique endoglucanase belonging to glycosyl hydorlase (GH) family 5 were determined. Methods: Based on Pfam analysis, the cellulases sequences containing FN3, Ig modules were extracted from 297 complete open reading frames (ORFs). The alkaline, thermostability, tertiary structure of deduced enzymes were predicted by AcalPred, TBI software, Phyre2 and Swiss models. Then, whole and truncated forms of a selected gene were expressed in Escherichia coli and purified by His-tag affinity column for assessment of FN3 ability to enhance enzyme activity, solubility and conformation. Results: From 297 complete ORFs coding for cellulases, 148 sequences containing FN3, Ig were identified. Mostly FN3 appeared in 90.9% beta-glucosidases belonging to glycosyl hydrolase family 3 (GH3) and situated downstream of catalytic domains. The Ig was found upstream of 100% endoglucanase GH9. Rarely FN3 was seen to be situated downstream of X domain and upstream of catalytic domain endoglucanase GH5. Whole enzyme (called XFN3GH5 based on modular structure) and truncate forms FN3, XFN3, FN3GH5, GH5 were cloned in pET22b (+) and pET22SUMO to be expressed in single and fusion forms with a small ubiquitin-related modifier partner (S). The FN3, SFN3 increased GH5 solubility in FN3GH5, SFN3GH5. The SFN3 partly served for GH5 conformation in SFN3GH5, increased modules interaction and enzyme-soluble substrate affinity to enhance SXFN3GH5, SFN3GH5 activities in mixtures. Both SFN3 and SXFN3 did not anchor enzyme on filter paper but exfoliate and separate cellulose chains on filter paper for enzyme hydrolysis. Conclusion: Based on these findings, the presence of FN3 module in certain cellulases was confirmed and it assisted for enzyme conformation and activity in both soluble and insoluble substrate.

Battery State of Charge Balancing Based on Low Bandwidth Communication in DC Microgrid

Duc-Khanh Hoang,Hong-Hee Lee 전력전자학회 2016 전력전자학술대회 논문집 Vol.2016 No.11

Advanced Magnetic Materials Produced by Using Rapid Quenching Technology

Nguyen Hoang Nghi,Nguyen Van Dung,Trinh Thi Thanh Nga,Bui Thi Khanh Nhung,Mai Thanh Tung,Nguyen Huu Tinh,Hoang Nhat Hieu,Bui Xuan Chien,Nguyen Thi Hong Tam 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.6

Amorphous alloys produced by using a rapid quenching technique are considered to be a precursor for producing nanosized and multiphase structures by precipitation (the top-down method). By using this technique, several new magnetic materials with different magnetic properties based on different physical mechanisms have been manufactured and investigated. Three new magnetic materials, a nanocrystalline soft magnetic material, a soft-hard permanent magnet and a Me-3d granular alloy with a GMR effect, what were prepared under local conditions, are presented and discussed in the experimental point of view. Amorphous alloys produced by using a rapid quenching technique are considered to be a precursor for producing nanosized and multiphase structures by precipitation (the top-down method). By using this technique, several new magnetic materials with different magnetic properties based on different physical mechanisms have been manufactured and investigated. Three new magnetic materials, a nanocrystalline soft magnetic material, a soft-hard permanent magnet and a Me-3d granular alloy with a GMR effect, what were prepared under local conditions, are presented and discussed in the experimental point of view.

X-ray absorption spectroscopies of Mg-Al-Ni hydrotalcite like compound for explaining the generation of surface acid sites

Hong Khanh Dieu Nguyen,Toan Dang Nguyen,Dung Ngoc Hoang,Duc Sy Dao,Thao Tien Nguyen,Limphirat Wanwisa,Lan Linh Hoang 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.2

Hydrotalcite-like compound containing metal cations such as Mg2+, Al3+ and Ni2+ was characterized using Ni K-edge EXAFS and in situ Ni K-edge XANES techniques for clarifying its bonding environment around Ni2+ sites and structure changes during calcination from room temperature to 550 oC, respectively. At the fixed molar ratio of Mg/Ni/Al of 2/1/1, the results obtained from EXAFS analysis showed a slight blue shift before and after the calcination at 550 oC and a reduction in white line peak; the best fits of the two samples revealed tiny change in coordination number about 7 for Ni-O path but considerable difference for Ni-Mg(Al) path from about 4.5 to 9.5, confirming a modification from brucite like to mixed oxide structure. On the other hand, bond distances of the Ni-O and Ni-Mg paths nearly fixed at about 2.06 Å to 3.0 Å reflected stability of the cationic bond order on each plane, but partial collapse and decomposition of the interlayer formed by water molecules and anion CO3 2− after the calcination. Linear combination fit extracted from the in situ Ni K-edge XANES also confirmed the changes along with the calcination such as slow and fast decreases of brucite fraction at 150 oC and 330 oC, respectively, in corresponding to the mixed oxide fraction increases. The achieved bonding structures were also applied to explain acid-base occurrence of the hydrotalcite-like material, especially the acid sites generated by different static charges along with the bonds. The explanation was illustrated by NH3-TPD method.