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Decentralized Neural Network-based Excitation Control of Large-scale Power Systems
Wenxin Liu,Jagannathan Sarangapani,Ganesh K. Venayagamoorthy,Li Liu,Donald C. Wunsch II,Mariesa L. Crow,David A. Cartes 대한전기학회 2007 International Journal of Control, Automation, and Vol.5 No.5
This paper presents a neural network based decentralized excitation controller design for large-scale power systems. The proposed controller design considers not only the dynamics of generators but also the algebraic constraints of the power flow equations. The control signals are calculated using only local signals. The transient stability and the coordination of the subsystem control activities are guaranteed through rigorous stability analysis. Neural networks in the controller design are used to approximate the unknown/imprecise dynamics of the local power system and the interconnections. All signals in the closed loop system are guaranteed to be uniformly ultimately bounded. To evaluate its performance, the proposed controller design is compared with conventional controllers optimized using particle swarm optimization. Simulations with a three-machine power system under different disturbances demonstrate the effectiveness of the proposed controller design.
A High Precision Time-frequency Analysis Method
Wenxin Zhang,Xiaojun Liu,Xiuwei Chen,Qing Liu,Guangyou Fang 보안공학연구지원센터 2015 International Journal of Signal Processing, Image Vol.8 No.7
To analysis the signal whose frequency changes as time, this article presents a new time-frequency analysis method based on short-time fractional Fourier transform (FRFT) and integration of midpoints. This method uses window functions to divide the signal to many pieces, then the FRFT is used to calculate the frequency modulation (FM) rate of each piece. A chirp signal can be built based on the FM rate and the intermediate frequency (IF) signal is obtained by mixing the chirp signal and the primary signal. The frequency of the midpoints can be estimated by the chirp-z transform (CZT), therefore the frequency of every piece can be calculated. This method avoids the impact that the quick change of frequency leads to the error of short-time Fourier transform. It also can reduce the error brought by the estimation of chirp rate. Therefore, the method can improve the accuracy of time-frequency analysis. This article also puts forward a method to search the order of fractional Fourier transform, and the computer simulation and measurement verifies the effectiveness of the proposed algorithm.
Power Converters Based Advanced Experimental Platform for Integrated Study of Power and Controls
Liu, Wenxin,Kim, Jang-Mok,Wang, Cheng,Im, Won-Sang,Liu, Liming,Xu, Hao IEEE 2018 IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS - Vol.14 No.11
<P>With increasing interest in smart grid and renewable energy, significant investments have been allocated to promote related studies. Since there is a wide spectrum of topics to study, it is necessary to have an advanced experimental platform that can accommodate both system- and component-level studies, both hardware and algorithm designs, and both teaching and research. Unfortunately, such experimental platform is not commercially available. In this paper, an advanced power electronics based experimental platform is introduced. The system is consisted of one OPAL-RT real-time simulator, two one-bus microgrid testbeds, and two modular multilevel converters. The subsystems can form a multiple-bus microgrid testbed if connected through emulated power lines. The system can provide real-time simulation, controller hardware-in-the-loop (HIL) simulation, and power HIL simulation for power systems study. Various converter topologies can be configured with the modular converters for power electronics study. Both real-time simulator and DSP control boards can be used to implement advanced control algorithms. The designs and experiences shared in the paper will benefit many researchers that are in need of such system and promote power and energy related studies.</P>
Liu, Wenxin,Guerrero, Josep M.,Kim, Jang-Mok IEEE 2017 IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS - Vol.13 No.5
<P>In this Special Section on Systems of Power Converters: Design, Modeling, Control, and Implementation, we have 11 high-quality papers approved for publication that cover the following three topics. 1) Converter Design and Operation. 2) Subsystem-Level Applications. 3) System-Level Applications. These topics and the corresponding papers are summarized.</P>
Wenxin Li,반규정,Da-Hao Zheng,Weixian Liu,이영호,Sue Yeon Lee,이준호,Suk-Ha Lee 한국작물학회 2008 Journal of crop science and biotechnology Vol.11 No.4
The bean bug Riptortus clavatus Thunberg (Heteroptera: Alydidae) is an important pest, causing serious yield loss in soybean. Butthe information on mechanism of resistance to R. clavatus is limited. The objective of this study was to identify QTLs for R. clavatusresistance using simple sequence repeat (SSR) markers in a soybean population of recombinant inbred lines (RILs) developed fromthe cross PI 171451 × Hwaeomputkong. A genetic map from this population was constructed with a total of 136 SSR markers covering1073.9 cM on 20 linkage groups (LGs). With 126 F5 RILs, two independent QTLs for resistance to R. clavatus were mapped onLGs B1 and C2. The amount of phenotypic variation explained by these QTLs ranged from 12 to 16%. PI 171451 showed an escaperesponse to R. clavatus. Under feeding conditions, 14.4% of RILs showed greater resistance to R. clavatus than the resistant parent. The resistance to R. clavatus in soybean from PI 171451 was incomplete and quantitatively inherited and the QTLs for resistance toR. clavatus detected in the RIL population were not significantly affected by epistatic interactions.
WEIGHTED ENDPOINT INEQUALITIES FOR MULTILINEAR MARCINKIEWICZ INTEGRAL OPERATOR
Wenxin, Yu,Liu, Lanzhe Korean Mathematical Society 2008 대한수학회보 Vol.45 No.1
We prove a sharp inequality for some multilinear operator related to Marcinkiewicz integral operator. As application, we obtain the weighted norm inequality and L log L type estimate for the multilinear operator.
Zhang WenXin,Li Hao,Cong Haofei,Zhou Ruifu,Qin Yuanbin,Xu Peilong,Liu Xuhai,Wang Fengyun 한국물리학회 2023 Current Applied Physics Vol.48 No.-
One-dimensional wide band-gap metal oxide semiconductors demonstrate enormous potential in high-performance ultraviolet photodetectors. Here, via tuned zinc oxide (ZnO) concentration ratio and heterojunction structure as well as decent VTH value, we electrospun tin zinc oxide (SnZnOX) nanowires for photoelectronic conversion function. The constructed optimized photodetectors based on Sn8Zn2OX nanowires can exhibit a remarkable detectivity of 1.77 × 1016 Jones, excellent responsivity of 2.23 × 103 A/W and relative high sensitivity over 104. In addition to the excellent photodetection performance, Sn8Zn2OX nanowire devices exhibit nonvolatile memory effect, which can maintain the light-induced low resistance state at 5 V without light. Moreover, a voltage of 30 V was applied to Sn8Zn2OX nanowires devices to realize light-writing state switching to bias-erasing state, and the device could come back to their initial high resistance state. These results indicate SnZnOX nanowires devices possess a tremendous potential in the circuit design of the artificial visual system.
Weighted endpoint Inequalities for Multilinear Marcinkiewicz Integral Operator
Yu Wenxin,Lanzhe Liu 대한수학회 2008 대한수학회보 Vol.45 No.1
We prove a sharp inequality for some multilinear operatorrelated to Marcinkiewicz integral operator. As application, we obtain theweighted norm inequality and Llog L type estimate for the multilinear operator.
Reliability‐aware service chaining mapping in NFV‐enabled networks
Yicen Liu,Yu Lu,Wenxin Qiao,Xingkai Chen 한국전자통신연구원 2019 ETRI Journal Vol.41 No.2
Network function virtualization can significantly improve the flexibility and effectiveness of network appliances via a mapping process called service function chaining. However, the failure of any single virtualized network function causes the breakdown of the entire chain, which results in resource wastage, delays, and significant data loss. Redundancy can be used to protect network appliances; however, when failures occur, it may significantly degrade network efficiency. In addition, it is difficult to efficiently map the primary and backups to optimize the management cost and service reliability without violating the capacity, delay, and reliability constraints, which is referred to as the reliability‐aware service chaining mapping problem. In this paper, a mixed integer linear programming formulation is provided to address this problem along with a novel online algorithm that adopts the joint protection redundancy model and novel backup selection scheme. The results show that the proposed algorithm can significantly improve the request acceptance ratio and reduce the consumption of physical resources compared to existing backup algorithms.