VT-ECE Graduate Events

Power Systems Analysis in the Power-Angle Domain (Dec 4)

2009-11-11T11:30:58-05:00

Fri, Dec 4, 2009
Power Systems Analysis in the Power-Angle Domain

Graduate Advisory Committee:
De La Reelopez, Jaime, Chair
Centeno, Virgilio A.
Liu, Yilu
Meehan, Kathleen
Phadke, Arun
Prather, Carl L.
Thorp, James S.

Abstract:
The idea of performing power systems dynamic analysis in the power-angle domain has been hinted at by previous researchers, but this may be the first published document to develop detailed techniques by which entire power systems can be represented and solved in the power-angle domain. With the widespread deployment of phasor measurement units and frequency data recorders the industry is looking for more real-time analytical tools to turn real-time wide-area measurements into useful information. Applications based on power-angle domain analysis are simple enough that they may be used online. Power-angle domain analysis is similar to DC load-flow techniques in that a flat voltage profile is used and it is assumed that real power and voltage angle are completely decoupled from reactive power and voltage magnitude. The linearized equations for the dynamics of generators and loads are included in the model, which allows the electromechanical response to be solved using conventional circuit analysis techniques. The effect of generation trips, load switching, and line switching can be quickly approximated with nodal analysis or mesh analysis in the power-angle domain. The analysis techniques developed here are not intended to be as accurate as time-domain simulation, but they have the advantages of being simpler, fast enough to be put online, and they provide a better analytical insight into the system. Power-angle domain analysis enables applications that are not readily available with conventional techniques, such as the estimation of electromechanical propagation delays based on system parameters, the formulation of electromechanical equivalents, modal analysis, stability analysis, and event location and identification based on a small number of angle or frequency measurements. Fault studies and contingency analysis are typically performed with detailed time-domain simulations, where the electromechanical response of the system is a function of every machine in the interconnection and the lines connecting them. All of this information is rarely known for the entire system for each operating condition; as a result, for many applications it may be more suitable to compute an approximation of the system response based on the current operating state of only the major lines and generators. Power-angle domain analysis is adept at performing such approximations.

Non-Negative Least Square Adjustment of C-Factors to Estimate Substation Peak Load (Dec 4)

2009-11-17T13:12:18-05:00

Fri, Dec 4, 2009
Non-Negative Least Square Adjustment of C-Factors to Estimate Substation Peak Load

Committee Members:
Robert Broadwater, Chair
Lynn Abbott, Member
Kwa-Sure Tam, Member

Abstract:
In order to accurately analyze and plan the power distribution system, correct loading information across the system is required. The customer billing information is used and the conversion factors and diversity factors are applied to the billing information to accurately estimate the time and the peak for a circuit.
The results on the industrial predominant circuits has been analyzed in this thesis and has been found to give the results which are over estimated by more than 100%. To provide improved results in case of industrial dominated circuits a new method has been proposed which utilizes the Supervisory Control and Data Acquisition (SCADA) data to provide better results. The load research statistics are calculated and the loads for particular customers are estimated. Circuits are chosen which are predominant in industrial class and the SCADA measurements for the particular circuits are obtained from the utility companies. The C-factors are then adjusted using the Non-Negative Least Squares (NNLS) algorithm and the new estimated values have been compared to the SCADA and have been found to provide improved results.

Camera Pose Corrections for Robust Stereo Imagery (Dec 4)

2009-11-17T13:15:02-05:00

Fri, Dec 4, 2009
Camera Pose Corrections for Robust Stereo Imagery

Committee Members:
Lynn Abbott, Co-Chair
Keven Kochersberger, Co-Chair
Robert Broadwater, Member

Abstract:
Mapping terrain from an unmanned aerial vehicle (UAV) is useful in building 3-D terrain models for analysis. These models can be used to plan safe routes for unmanned ground vehicles (UGV). The models are created from point clouds, which are a collection of points in 3-D space found by using a stereo vision camera. A stereo vision camera is a system that utilizes images of the terrain from two different viewpoints. An ideal stereo vision system requires that the cameras are aligned in parallel, if not; the orientations are known a prior. There are various stereo systems commercially available, however at times it becomes necessary to develop a custom system tailored for a specific application. When mapping terrain from a fixed wing UAV from a high altitude, it is necessary to place the cameras on the wing tips to achieve an appropriate baseline. This method of mounting cameras for a stereo system is problematic due to the deflection of the wings during a flight. This offset forces the cameras to deviate from their calibrated orientation which causes errors in producing 3-D points. This thesis provides a detailed look into developing a custom stereo vision system for terrain mapping on board a vertical takeoff and landing (VTOL) UAV. In addition, a method is proposed to stabilize a stereo system on a fixed wing UAV by attaching accelerometers to capture images at the height of the deflection frequency and obtain the position offset from norm to adjust accordingly.

Deadbeat Current Control of a Switched Reluctance Motor (Dec 4)

2009-11-19T09:16:59-05:00

Fri, Dec 4, 2009
Deadbeat Current Control of a Switched Reluctance Motor

Committee Members:
Krishnan Ramu, Chair
William Baumann, Member
Daniel Stilwell, Member

Abstract:
High performance current control is critical to the success of the switched reluctance motor(SRM). Yet high motor phase nonlinearities in the SRM place extra burden on the current controller, rendering it the weakest link in SRM control. In contrast to linear motor control techniques which respond to current error, the deadbeat controller calculates the control voltage by the current command, phase current, rotor angle and DC link voltage. The deadbeat controller has demonstrated superior response in three phase inverter current control, PM motor current control, and other relatively linear control applications. This study will investigate the viability and performance of a deadbeat controller for the highly nonlinear SRM. The need for an accurate deadbeat control model first motivates the investigation of experimental inductance measurement techniques. A deadbeat control law is then proposed through multiple revisions to demonstrate the benefit of the numerical method chosen to derive the controller and a current predictor which compensates for processor latency and PWM delay. The practical problems of loop delay, feedback noise, feedback filtering, and deadbeat controller parameter sensitivity are investigated by linear analysis, simulation, experimental implementation and model analysis. Simulation and implementation verify deadbeat performance and various measures of transient performance are presented. To address the problem of SRM model error the study ends with a brief discussion of adaptive deadbeat control modifications for possible future research.

Propagation of Electromechanical Disturbances across Large Interconnected Power Systems and Extraction of Associated Modal Content from Measurement Data (Dec 4)

2009-11-20T15:45:33-05:00

Fri, Dec 4, 2009
Propagation of Electromechanical Disturbances across Large Interconnected Power Systems and Extraction of Associated Modal Content from Measurement Data

Ph.D. exam for Jason Bank (EE), 457 Whittemore at 4 pm

Coarse Classifier Implementation Using a Hybrid FPGA/DSP/GPP SDR Platform (Dec 7)

2009-11-13T13:35:06-05:00

Mon, Dec 7, 2009
Coarse Classifier Implementation Using a Hybrid FPGA/DSP/GPP SDR Platform

Committee Members:
Charles Bostian, Chair
Allen MacKenzie, Member
Cameron Patterson, Member

Abstract:
Although there is a lot of research happening in the field of signal classification, there is very little emphasis on hardware implementation. This thesis concentrates on the hardware implementation of a Universal Classification Synchronization system on a hybrid FPGA/DSP/GPP based software defined radio platform. The advantages of using a hybrid software radio platform are discussed and the tool chain necessary to develop applications on such hardware platforms is analyzed. The roadmap to building a signal recognition system includes taking advantage of the FGPA to implement a fast wideband multichannel sensor which takes advantage of the parallelism offered by the FPGA. Also the functionality of the UCS algorithm is further extended to classify wideband signals like OFDM and performance measurements are given.

Frequency Monitoring Network (FNET) Algorithm Improvements and Application Development (Dec 7)

2009-11-20T15:45:33-05:00

Mon, Dec 7, 2009
Frequency Monitoring Network (FNET) Algorithm Improvements and Application Development

Ph.D. exam for Tao Xia. 457 Whittemore at 10 am.

Circuit Design Methods with Emerging Nanotechnologies (Dec 8)

2009-11-12T15:13:00-05:00

Tue, Dec 8, 2009
Circuit Design Methods with Emerging Nanotechnologies

Committee Members:
Huang, Chao, Chair
Cao, Yang
Hsiao, Michael S.
Schaumont, Patrick Robert
Yang, Yaling

Abstract:
As complementary metal-oxide semiconductor (CMOS) technology faces more and more severe physical barriers down the path of continuously feature size scaling, innovative nano-scale devices and other post-CMOS technologies have been developed to enhance future circuit design and computation. These nanotechnologies have shown promising potentials to achieve magnitude improvement in performance and integration density. The substitution of CMOS transistors with nano-devices is expected to not only continue along the exponential projection of Moore's Law, but also raise significant challenges and opportunities, especially in the field of electronic design automation. The major obstacles that the designers are experiencing with emerging nanotechnology design include: i) the existing computer-aided design (CAD) approaches in the context of conventional CMOS Boolean design cannot be directly employed in the nanoelectronic design process, because the intrinsic electrical characteristics of many nano-devices are not best suited for Boolean implementations but demonstrate strong capability for implementing non-conventional logic such as threshold logic and reversible logic; ii) due to the density and size factors of nanodevices, the defect rate of nanoelectronic system is much higher than conventional CMOS systems, therefore existing design paradigms cannot guarantee design quality and lead to even worse result in high failure ratio. Motivated by the compelling potentials and design challenges of emerging post-CMOS technologies, this dissertation work focuses on fundamental design methodologies to effectively and efficiently achieve high quality nanoscale design. A novel programmable logic element (PLE) is first proposed to explore the versatile functionalities of threshold logic. This PLE structure is mathematically proven to be logic complete. Based on the PLEs, a reconfigurable architecture is constructed to offer dynamic reconfigurability with little or no reconguration overhead, due to the intrinsic self-latching property of nanopipelining. To fully take advantage of such threshold logic designs using emerging nanotechnologies, we also developed a combinational equivalence checking (CEC) framework, which greatly reduces the verication time. Then the reversible logic synthesis problem is considered as we focus on efficient synthesis heuristics which can provide high quality synthesis results within a reasonable computation time. We have developed a weighted directed graph model for function representation and complexity measurement. An atomic transformation is constructed to associate the function complexity variation with reversible gates. The efficiency of our heuristic lies in maximally decreasing the function complexity during synthesis steps as well as the capability to climb out of local optimums. To tackle the high defect-rate during the emerging nanotechnology manufacturing process, we have developed a novel defect-aware logic mapping framework for nanowirebased PLA architecture via Boolean satisfiability (SAT). The PLA defects of various types are formulated as covering and closure constraints. The defect-aware logic mapping is then solved efficiently by using available SAT solvers. This approach can generate valid logic mapping with a defect rate as high as 20%.

Phishing on Secured WLANs: Threat and Preventive Measure (Dec 8)

2009-11-19T15:47:03-05:00

Tue, Dec 8, 2009
Phishing on Secured WLANs: Threat and Preventive Measure

Committee Members:
Yaling Yang, Chair
Thomas Hou, Member
Anil Vullikanti, Member

Abstract:
The thesis shows the possibility of a phishing attack on secured, private Wireless LANs. Private WLANs which use a login page to authenticate users in hotels, airports and academic campuses are all vulnerable to this attack. Virginia Tech's WLAN is used as an example to show that the attack is possible. The attack combines two very well known attacks: one is to deceptively guide a user into logging into a fake website, which shows similar log-in page to the page of the website the user intends to go to, and the second attack is to show users a valid certificate, which does not even show a warning. (The rogue server takes the user to a log-in page which is similar to Virginia Tech's log-in page and shows him a valid security certificate.) We present a solution to the proposed problem. A software is implemented that runs on Windows Vista. The software warns the user if there are servers with more than one type of security certificates, claiming to be from one same network. Experiments are done to show the feasibility of the software. We contrast our method to already existing methods, and show in what respects our solution is better. The biggest advantage of this method is that it involves no change on the server side. It is not needed that the users have any prior knowledge of the network (which is very helpful when the users access WLAN at airports and hotels). Also, when using this method, the user does not need to connect to any network, and is still able to get a warning. It however, requires the user to be able to differentiate between the real and fake networks after the user has been warned.

Cognitive Gateway to Promote Interoperability, Coverage and Throughput in Heterogeneous Communication Systems (Dec 8)

2009-11-20T15:45:33-05:00

Tue, Dec 8, 2009
Cognitive Gateway to Promote Interoperability, Coverage and Throughput in Heterogeneous Communication Systems

Ph.D. exam for Qinqin Chen. 457 Whittemore at 8:30 am.

Methodology for a Security-Dependability Adaptive Protection Scheme based on Data Mining (Dec 9)

2009-11-17T13:03:17-05:00

Wed, Dec 9, 2009
Methodology for a Security-Dependability Adaptive Protection Scheme based on Data Mining

Graduate Advisory Committee:
Centeno, Virgilio A, Co-Chair
Thorp, James S, Co-Chair
De La Reelopez, Jaime
Kohler, Werner E
Silva, Luiz A

Abstract:
The power industry is currently in the process of re-inventing itself. The unbundling of the traditional monopolistic structure that gave birth to a deregulated electricity market, the mass tendency towards a greener use of energy, the new emphasis on distributed generation and alternative renewable resources, and new emerging technologies have revolutionized the century old industry. Recent blackouts offer testimonies of the crucial role played by protection relays in a reliable power system. It is argued that embracing the paradigm shift of adaptive protection is a fundamental step towards a smart power grid. The adaptive philosophy of protection systems acknowledges that relays may change their characteristics in order to tailor their operation to the prevailing system conditions. The purpose of this dissertation is to present a methodology to implement a security/dependability adaptive protection scheme. It is argued that the likelihood of hidden failures and potential cascading events can be significantly reduced by adjusting the security/dependability balance of protection systems to better suit prevailing system conditions. The proposed methodology is based on Wide Area Measurements (WAMs) obtained with the aid of Phasor Measurement Units (PMUs). A Data Mining algorithm known as Decision Trees is used to classify the power system state and to predict the optimal security/dependability bias of a critical protection scheme.

Energy Tradeoff Between Routing Data and Computation in Wireless Sensor Networks (Dec 9)

2009-11-20T15:35:53-05:00

Wed, Dec 9, 2009
Energy Tradeoff Between Routing Data and Computation in Wireless Sensor Networks

Committee Members:
Yaling Yang, Chair
Thomas Hou, Member
Paul Plassmann, Member

Abstract:
Wireless sensor networks is a rapidly growing field with new technologies emerging, new applications being developed and standards being finalized. Unlike present information services which are available on internet which can get stale or be useless because its too generic, sensor networks promise to give the end information precisely localized in time or space, according to the user needs or demands. In recent years, advances in microelectronics have allowed the development of small devices that consume less power and are cost-efficient with the ability to sense, process, and communicate data. A critical issue in these devices is represented by the limited availability of energy. Two factors that affect the energy consumption of the sensor network are computation and communication. By simply processing the acquired data at a node and transmitting, it results in inefficient use of energy. The focus in this project is on analyzing the tradeoff between the energy spent for routing the data in the sensor network and energy consumed for processing of data at sensor nodes to avoid transmission of redundant data.

Analysis of Handoff Performance in 802.11 Networks (Dec 9)

2009-11-20T15:56:05-05:00

Wed, Dec 9, 2009
Analysis of Handoff Performance in 802.11 Networks

Committee Members:
Yaling Yang, Chair
Ashwin Amanna, Member
Thomas Hou, Member
Jung-Min Park, Member

Abstract:
Wireless networks based on the IEEE 802.11 standard have become very prevalent recently. Most of these networks support only nomadic mobility of wireless devices. However, in case of vehicle-to-infrastructure communications the mobile devices in the vehicles need to have the ability to quickly switch their association to a new access points when they move out of range of their initial access point. Wireless devices operating in the 5 GHz band have to share the frequency band with military and weather radar systems. Such devices are required to employ dynamic frequency selection (DFS) to detect the presence of radar signals and switch channels in order to avoid interfering with the radar. As the radio needs to constantly monitor the channel for radar signals it puts an overhead on the tasks that the radio has to perform including handoff in case of mobile devices. This report explains the basics of 802.11 MAC layer handoff process. We analyze the handoff performance of 802.11 networks in the 5 GHz band on an outdoor one-mile test bed and discuss potential implications of the DFS requirement on this performance.

Position Location Techniques: A Survey (Dec 11)

2009-11-18T07:59:52-05:00

Fri, Dec 11, 2009
Position Location Techniques: A Survey

Committee Members:
Michael Buehrer, Chair
Tamal Bose, Member
da Silva, Claudio, Member

Abstract:
Modern cellular phones usually incorporate some location based service into their functionality, be it for navigation, or vehicle tracking, or just to identify the user’s current location. Newer smartphones mostly use GPS capabilities, but older phones used other procedures ranging from the basic Cell of Origin method to more advanced GSM positioning techniques that use some form of multilateration. This project takes a look at techniques used for position location in traditional (standalone) GPS systems, as well as the other, older methods. In conclusion, it includes a brief overview of the Assisted GPS system, which is usually used by smartphones.

Introduction to Radar Analysis (Dec 16)

2009-11-23T07:59:56-05:00

Wed, Dec 16, 2009
Introduction to Radar Analysis

Committee Members:
Joe Tront, Chair
Lynn Abbott, Member
Peter Athanas, Member

Abstract:
This project is in the area of Engineering Education, and its purpose is to develop a multimedia-based lecture that undergraduate and graduate electrical engineering students can use to gain a basic understanding of radar and radar analysis. The overall lecture is divided into four primary presentations, a MATLAB demo of an analysis tool, and a summary presentation. The four presentation topics are Radar Fundamentals, The Radar Range Equation, Atmospheric Affects, and Probability of Detection and Track. The MATLAB demo is a GUI built around the radar range equation, and will allow students to develop a simple radar design and then run a simulation in order to understand the performance of the radar based on the their chosen parameters. The code for this tool will be provided as a part of the lecture so students will be able to run their own simulations at any time. The code is also completely open so that students wishing to learn how to write a MATLAB GUI can use this code as a template. The summary presentation will briefly review the topics discussed and provide references for further self-study. The entire lecture will be narrated and organized onto a menu-based DVD that will run on any DVD Player or computer.