Browsing by Author "Zhu, Dan"
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- Electric Distribution Reliability Analysis Considering Time-varying Load, Weather Conditions and Reconfiguration with Distributed GenerationZhu, Dan (Virginia Tech, 2007-03-27)This dissertation is a systematic study of electric power distribution system reliability evaluation and improvement. Reliability evaluation of electric power systems has traditionally been an integral part of planning and operation. Changes in the electric utility coupled with aging electric apparatus create a need for more realistic techniques for power system reliability modeling. This work presents a reliability evaluation technique that combines set theory and Graph Trace Analysis (GTA). Unlike the traditional Markov approach, this technique provides a fast solution for large system reliability evaluation by managing computer memory efficiently with iterators, assuming a single failure at a time. A reconfiguration for restoration algorithm is also created to enhance the accuracy of the reliability evaluation, considering multiple concurrent failures. As opposed to most restoration simulation methods used in reliability analysis, which convert restoration problems into mathematical models and only can solve radial systems, this new algorithm seeks the reconfiguration solution from topology characteristics of the network itself. As a result the new reconfiguration algorithm can handle systems with loops. In analyzing system reliability, this research takes into account time-varying load patterns, and seeks approaches that are financially justified. An exhaustive search scheme is used to calculate optimal locations for Distributed Generators (DG) from the reliability point of view. A Discrete Ascent Optimal Programming (DAOP) load shifting approach is proposed to provide low cost, reliability improvement solutions. As weather conditions have an important effect on distribution component failure rates, the influence of different types of storms has been incorporated into this study. Storm outage models are created based on ten years' worth of weather and power outage data. An observer is designed to predict the number of outages for an approaching or on going storm. A circuit corridor model is applied to investigate the relationship between power outages and lightning activity.
- One thousand plant transcriptomes and the phylogenomics of green plantsLeebens-Mack, James H.; Barker, Michael S.; Carpenter, Eric J.; Deyholos, Michael K.; Gitzendanner, Matthew A.; Graham, Sean W.; Grosse, Ivo; Li, Zheng; Melkonian, Michael; Mirarab, Siavash; Porsch, Martin; Quint, Marcel; Rensing, Stefan A.; Soltis, Douglas E.; Soltis, Pamela S.; Stevenson, Dennis W.; Ullrich, Kristian K.; Wickett, Norman J.; DeGironimo, Lisa; Edger, Patrick P.; Jordon-Thaden, Ingrid E.; Joya, Steve; Liu, Tao; Melkonian, Barbara; Miles, Nicholas W.; Pokorny, Lisa; Quigley, Charlotte; Thomas, Philip; Villarreal, Juan Carlos; Augustin, Megan M.; Barrett, Matthew D.; Baucom, Regina S.; Beerling, David J.; Benstein, Ruben Maximilian; Biffin, Ed; Brockington, Samuel F.; Burge, Dylan O.; Burris, Jason N.; Burris, Kellie P.; Burtet-Sarramegna, Valerie; Caicedo, Ana L.; Cannon, Steven B.; Cebi, Zehra; Chang, Ying; Chater, Caspar; Cheeseman, John M.; Chen, Tao; Clarke, Neil D.; Clayton, Harmony; Covshoff, Sarah; Crandall-Stotler, Barbara J.; Cross, Hugh; dePamphilis, Claude W.; Der, Joshua P.; Determann, Ron; Dickson, Rowan C.; Di Stilio, Veronica S.; Ellis, Shona; Fast, Eva; Feja, Nicole; Field, Katie J.; Filatov, Dmitry A.; Finnegan, Patrick M.; Floyd, Sandra K.; Fogliani, Bruno; Garcia, Nicolas; Gateble, Gildas; Godden, Grant T.; Goh, Falicia (Qi Yun); Greiner, Stephan; Harkess, Alex; Heaney, James Mike; Helliwell, Katherine E.; Heyduk, Karolina; Hibberd, Julian M.; Hodel, Richard G. J.; Hollingsworth, Peter M.; Johnson, Marc T. J.; Jost, Ricarda; Joyce, Blake; Kapralov, Maxim V.; Kazamia, Elena; Kellogg, Elizabeth A.; Koch, Marcus A.; Von Konrat, Matt; Konyves, Kalman; Kutchan, Toni M.; Lam, Vivienne; Larsson, Anders; Leitch, Andrew R.; Lentz, Roswitha; Li, Fay-Wei; Lowe, Andrew J.; Ludwig, Martha; Manos, Paul S.; Mavrodiev, Evgeny; McCormick, Melissa K.; McKain, Michael; McLellan, Tracy; McNeal, Joel R.; Miller, Richard E.; Nelson, Matthew N.; Peng, Yanhui; Ralph, Paula E.; Real, Daniel; Riggins, Chance W.; Ruhsam, Markus; Sage, Rowan F.; Sakai, Ann K.; Scascitella, Moira; Schilling, Edward E.; Schlosser, Eva-Marie; Sederoff, Heike; Servick, Stein; Sessa, Emily B.; Shaw, A. Jonathan; Shaw, Shane W.; Sigel, Erin M.; Skema, Cynthia; Smith, Alison G.; Smithson, Ann; Stewart, C. Neal, Jr.; Stinchcombe, John R.; Szovenyi, Peter; Tate, Jennifer A.; Tiebel, Helga; Trapnell, Dorset; Villegente, Matthieu; Wang, Chun-Neng; Weller, Stephen G.; Wenzel, Michael; Weststrand, Stina; Westwood, James H.; Whigham, Dennis F.; Wu, Shuangxiu; Wulff, Adrien S.; Yang, Yu; Zhu, Dan; Zhuang, Cuili; Zuidof, Jennifer; Chase, Mark W.; Pires, J. Chris; Rothfels, Carl J.; Yu, Jun; Chen, Cui; Chen, Li; Cheng, Shifeng; Li, Juanjuan; Li, Ran; Li, Xia; Lu, Haorong; Ou, Yanxiang; Sun, Xiao; Tan, Xuemei; Tang, Jingbo; Tian, Zhijian; Wang, Feng; Wang, Jun; Wei, Xiaofeng; Xu, Xun; Yan, Zhixiang; Yang, Fan; Zhong, Xiaoni; Zhou, Feiyu; Zhu, Ying; Zhang, Yong; Ayyampalayam, Saravanaraj; Barkman, Todd J.; Nam-Phuong Nguyen; Matasci, Naim; Nelson, David R.; Sayyari, Erfan; Wafula, Eric K.; Walls, Ramona L.; Warnow, Tandy; An, Hong; Arrigo, Nils; Baniaga, Anthony E.; Galuska, Sally; Jorgensen, Stacy A.; Kidder, Thomas I.; Kong, Hanghui; Lu-Irving, Patricia; Marx, Hannah E.; Qi, Xinshuai; Reardon, Chris R.; Sutherland, Brittany L.; Tiley, George P.; Welles, Shana R.; Yu, Rongpei; Zhan, Shing; Gramzow, Lydia; Theissen, Gunter; Wong, Gane Ka-Shu (2019-10-31)Green plants (Viridiplantae) include around 450,000-500,000 species(1,2) of great diversity and have important roles in terrestrial and aquatic ecosystems. Here, as part of the One Thousand Plant Transcriptomes Initiative, we sequenced the vegetative transcriptomes of 1,124 species that span the diversity of plants in a broad sense (Archaeplastida), including green plants (Viridiplantae), glaucophytes (Glaucophyta) and red algae (Rhodophyta). Our analysis provides a robust phylogenomic framework for examining the evolution of green plants. Most inferred species relationships are well supported across multiple species tree and supermatrix analyses, but discordance among plastid and nuclear gene trees at a few important nodes highlights the complexity of plant genome evolution, including polyploidy, periods of rapid speciation, and extinction. Incomplete sorting of ancestral variation, polyploidization and massive expansions of gene families punctuate the evolutionary history of green plants. Notably, we find that large expansions of gene families preceded the origins of green plants, land plants and vascular plants, whereas whole-genome duplications are inferred to have occurred repeatedly throughout the evolution of flowering plants and ferns. The increasing availability of high-quality plant genome sequences and advances in functional genomics are enabling research on genome evolution across the green tree of life.
- Power System Reliability Analysis with Distributed GeneratorsZhu, Dan (Virginia Tech, 2003-05-15)Reliability is a key aspect of power system design and planning. In this research we present a reliability analysis algorithm for large scale, radially operated (with respect to substation), reconfigurable, electrical distribution systems. The algorithm takes into account equipment power handling constraints and converges in a matter of seconds on systems containing thousands of components. Linked lists of segments are employed in obtaining the rapid convergence. A power flow calculation is used to check the power handling constraints. The application of distributed generators for electrical distribution systems is a new technology. The placement of distributed generation and its effects on reliability is investigated. Previous reliability calculations have been performed for static load models and inherently make the assumption that system reliability is independent of load. The study presented here evaluates improvement in reliability over a time varying load curve. Reliability indices for load points and the overall system have been developed. A new reliability index is proposed. The new index makes it easier to locate areas where reliability needs to be improved. The usefulness of this new index is demonstrated with numerical examples.
- Transmission and Distribution Real-Time Analysis Software for Monitoring and Control: Design and Simulation TestingZhu, Dan; Dilek, Murat; Zhong, Max; Parchure, Abhineet; Broadwater, Robert; Cincotti, Nicholas; Kutchen, Timothy; Placide, Scott; Watson, Luan (MDPI, 2023-05-16)The US electric grid is facing operational, stability, and security challenges. Transmission system operators need some measure of visibility into distribution system renewable generation. Distribution system generation needs to support transmission system voltage. The grid is experiencing an expansion in measurement systems. How to take full advantage of this expansion and defend against attacks, both cyber and physical, poses additional challenges. This paper introduces software designed to meet these challenges. At the center of the software is an Integrated System Model (ISM) that spans from transmission to secondary distribution. The ISM is employed in real-time abnormality detection, voltage stability forecasting, and multi-mode control. The software architecture along with selected analysis modules is presented. Testing results are presented for: 1—attacks on utility infrastructure; 2—energy savings from optimal control; 3—distribution system control response during a low voltage transmission system event; 4—cyber-attacks on PV inverters, where physical inverters are used in hardware-in-the-simulation-loop studies. Contributions of this work include real-time analysis that spans from three-phase transmission through secondary distribution; an approach for detecting abnormalities that employs measurements from three independent measurement systems; and a multi-mode distribution system control that responds to cyber-attacks, physical attacks, equipment failures, and transmission system needs.