AC Network Response Behaviors to Time-Varying Amplitude-Frequency Internal Voltage of Voltage Source Converters

Zhenhai Xie,Yuanzhu Chang,Jiabing Hu 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

During an AC fault, voltage source converter (VSC) has a different excitation-response characteristic compared with the synchronous generator (SG). As a result, for power systems with a high penetration of VSC-based equipment, the network response behaviors are mainly determined by the VSCs’ internal voltage whose amplitude and frequency are time-varying. However, the lumped parameter π-equivalent circuit model is established based on a sine steady-state signal. Thus, in order to analyze the network response behavior, an excitation-response relation model of AC network is proposed. Then, the response behaviors of node-voltage vectors are compared when using two different types line model in electromagnetic transient program (EMTP). Finally, the determinants of network response behaviors are analyzed. The conclusions of this paper indicate that the π-equivalent circuit model is improper and the distributed parameter line model is suggested to simulate the transient behaviors of a power system with high penetration of VSCs.

Damping BGP Route Flaps

Duan, Zhenhai,Chandrashekar, Jaideep,Krasky, Jeffrey,Xu, Kuai,Zhang, Zhi-Li The Korea Institute of Information and Commucation 2007 Journal of communications and networks Vol.9 No.4

BGP route flap damping(RFD) was anecdotally considered to be a key contributor to the stability of the global Internet inter-domain routing system. However, it was recently shown that RFD can incorrectly suppress for substantially long periods of time relatively stable routes, i.e., routes that only fail occasionally. This phenomenon can be attributed to the complex interaction between BGP path exploration and how the RFD algorithm identifies route flaps. In this paper we identify a distinct characteristic of BGP path exploration following a single network event such as a link or router failure. Based on this characteristic, we distinguish BGP route updates during BGP path exploration from route flaps and propose a novel BGP route flap damping algorithm, RFD+. RFD+ has a number of attractive properties in improving Internet routing stability. In particular, it can correctly suppress persistent route flaps without affecting routes that only fail occasionally. In addition to presenting the new algorithm and analyzing its properties, we also perform simulation studies to illustrate the performance of the algorithm.

On QoS Routing and Path Establishment in the Presence of Imprecise State Information

Yuan, Xin,Duan, Zhenhai The Korea Institute of Information and Commucation 2007 Journal of communications and networks Vol.9 No.4

In large networks, maintaining precise global network state information is impossible. The imprecise network state information has significant impacts on Quality-of-Service(QoS) routing and path establishment. In this paper, we develop analytical models for investigating the QoS routing schemes that are designed to tolerate imprecise network state information, and study the performance of various QoS routing schemes, including randomized routing, multi-path routing, and probability based routing, using both the models and simulations. We further propose a new mechanism, called local rerouting, that improves the effectiveness of QoS path establishment in the presence of imprecise global network state information. Local rerouting is orthogonal to existing schemes for dealing with imprecise state information and can be used in conjunction with them to alleviate the impacts of the imprecise information. The results of our performance study indicate that local rerouting is robust and effective.

Grid Scheduling Strategy Considering Electric Vehicles Participating in Multi-microgrid Interaction

Yu Zexu,Dou Zhenhai,Zhao Ye,Xie Ruishuo,Qiao Mengmeng,Wang Yuanyuan,Liu Lianxin 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.3

With the expansion of the scale of power grid and the increase of the number of microgrids, the energy interaction between microgrids using contact lines will greatly increase the computation of the superior dispatching center. Therefore, the contact lines between microgrids are cancelled, so that the microgrids can realize energy interaction through the distribution network. However, this method may lead to overload of distribution network connections while reducing the computation. Due to its good transfer characteristics, the addition of electric vehicles (EVs) can alleviate the contact line pressure and realize the load transfer of microgrids. On this basis, a grid dispatching model based on the participation of EVs in microgrid interaction is proposed. Contact lines between microgrids are replaced by EVs and 100% transmission through the distribution network. The grid load is optimized with the goal of minimizing total cost, maximizing renewable energy utilization, and maximizing profit of each integrator. In the process of model optimization, aiming at the problem that the speed factor in the particle swarm optimization algorithm cannot take into account the optimal direction and the optimal step size, the adaptive time factor is added to establish a two-layer improved particle swarm optimization algorithm, which realizes the cooperative optimization of load and electricity price. The simulation results show that the total cost and underutilization of renewable energy of IEEE33-node system are reduced by 13.79% and 67.85%, compared with the traditional interaction mode, while they are reduced by 0.425% and 6.11% in IEEE43-node system.

Optimization of Capacity Configuration of Wind–Solar–Diesel–Storage Using Improved Sparrow Search Algorithm

Dong Jun,Dou Zhenhai,Si Shuqian,Wang Zichen,Liu Lianxin 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.1

In order to reasonably allocate the capacity of distributed generation and realize the goal of stable, economic and clean operation of the system, a multi-objective optimization model with investment cost, environmental protection and power supply quality as indicators has been established, and the multi-objective sparrow search algorithm is used to optimize the solution. Although the multi-objective search algorithm is more effi cient than the traditional single objective algorithm, it is easy to fall into local optimum. To this end, the niche optimization technology is used to improve the optimization eff ect of multi-objective sparrow search algorithm, and the Levy fl ight strategy is introduced to enhance the ability of multi-objective sparrow search algorithm to jump out of local optimum. The calculation example uses the traditional multi-object search algorithm and the niche multi-objective sparrow search algorithm with levy disturbance to solve the proposed model. The simulation results verify the eff ectiveness of the multi-objective sparrow search algorithm improved by levy disturbance and niche optimization technology

A Time Dependent Analysis of Thermal Environment in Beehouse

Lee Suk Gun,Li Zhenhai,Choi Kwang Soo 한국생물환경조절학회 1997 한국생물환경조절학회 학술발표논문집 Vol.6 No.2

Equine Arteritis Virus Does Not Induce Interferon Production in Equine Endothelial Cells: Identification of Nonstructural Protein 1 as a Main Interferon Antagonist

Go, Yun Young,Li, Yanhua,Chen, Zhenhai,Han, Mingyuan,Yoo, Dongwan,Fang, Ying,Balasuriya, Udeni B. R. Hindawi Publishing Corporation 2014 BioMed research international Vol.2014 No.-

<P>The objective of this study was to investigate the effect of equine arteritis virus (EAV) on type I interferon (IFN) production. Equine endothelial cells (EECs) were infected with the virulent Bucyrus strain (VBS) of EAV and expression of IFN-<I><I>β</I></I> was measured at mRNA and protein levels by quantitative real-time RT-PCR and IFN bioassay using vesicular stomatitis virus expressing the green fluorescence protein (VSV-GFP), respectively. Quantitative RT-PCR results showed that IFN-<I><I>β</I></I> mRNA levels in EECs infected with EAV VBS were not increased compared to those in mock-infected cells. Consistent with quantitative RT-PCR, Sendai virus- (SeV-) induced type I IFN production was inhibited by EAV infection. Using an IFN-<I><I>β</I></I> promoter-luciferase reporter assay, we subsequently demonstrated that EAV nsps 1, 2, and 11 had the capability to inhibit type I IFN activation. Of these three nsps, nsp1 exhibited the strongest inhibitory effect. Taken together, these data demonstrate that EAV has the ability to suppress the type I IFN production in EECs and nsp1 may play a critical role to subvert the equine innate immune response.</P>

BCN Graphene as Efficient Metal‐Free Electrocatalyst for the Oxygen Reduction Reaction

Wang, Shuangyin,Zhang, Lipeng,Xia, Zhenhai,Roy, Ajit,Chang, Dong Wook,Baek, Jong‐,Beom,Dai, Liming WILEY‐VCH Verlag 2012 Angewandte Chemie Vol.124 No.17

<P><B>Einen einfachen Zugang</B> zu B,N‐dotiertem Graphen mit einstellbarer Zusammensetzung eröffnet das Tempern von Graphenoxid in Gegenwart von Borsäure und Ammoniak. Das gebildete BCN‐Graphen (siehe Bild; C grau, H weiß, B rosa, N blau) ist bei der Sauerstoffreduktion in alkalischem Milieu ein aktiverer Katalysator als kommerzielle Pt/C‐Elektrokatalysatoren.</P>

Evaluation Model of Buyers’ Dynamic Reputation in E-commerce

Yang Zhang,Tieying Liu,Ru Li,Zhenhai Wan 보안공학연구지원센터 2015 International Journal of Multimedia and Ubiquitous Vol.10 No.5

Members in electronic commerce often have no information about each other, thus, trust is one of the most important aspects in online transaction. In order to accurately display the buyers’ trustworthiness. This paper constructs a mean model to compute reputation of buyers. The model is based on two aspects, successful trading and returned goods. We introduce two adaptive trust factors, transaction value factor and return rate factor, to improve the feedback rates of sellers. Contrasting reputation based solely on feedback from sellers, the reputation of buyers is eventually represented by a three-dimensional array in our model. Simulation experiments evaluated different buyers and a buyer’s different period dynamic reputation. Compared with existing rating models, this model is more effective and can increase the ability to resist fraud.

Residual current fault type recognition based on S3VM and KNN cooperative training

Zhang, Xiangke,Wang, Yajing,Dou, Zhenhai,Wang, Wei,Bai, Yunpeng The Korean Institute of Power Electronics 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.11

It is difficult to detect the residual current of specific fault types in low-voltage distribution networks, which results in few labeled residual current samples. Thus, it is difficult to recognize the fault types of residual current. To solve this problem, a cooperative training classification model based on an improved squirrel search algorithm (ISSA) for a semi-supervised support vector machine (S3VM) and the k-nearest neighbor (KNN) is proposed (ISSA-S3VM-KNN). First, the residual current is decomposed into k intrinsic mode functions (IMFs) by variational mode decomposition (VMD), and the characteristic parameters of the IMFs are extracted to obtain a characteristic dataset for establishing a classification model. Second, to solve the problem where it is difficult to the select parameters (such as the penalty factors, slack variables and kernel function) of a S3VM, an ISSA parameter optimization method is proposed to self-adaptively select the optimal combination of parameters for the S3VM. Finally, the KNN is used to verify the classification results of an ISSA-S3VM through cooperative training, which further improves the classification accuracy of the S3VM for unlabeled residual current samples. Classification results of measured and simulation data show that the classification accuracy of the ISSA-S3VM-KNN is higher than that of the SVM-BPNN, WE-AE-BPNN, and PSO-SVM. The ISSA-S3VM-KNN provides a certain theoretical basis for achieving fast and accurate residual current fault type recognition.