Electrical and Electronics Commons^™

Steady-State Voltage Security Assessment Using Symmetric Eigenvalue Analysis For Weak Area Identification In Large Power Transmission Network, Yagnaramasubramanian Somayajulu

Theses and Dissertations

The central focus of this thesis is on long-term static voltage stability analysis of large power transmission grid. This thesis work is a product of an attempt to comprehend the numerous researches that has been done over the years on voltage security assessment. Voltage stability is one of the essential components influencing the reliability of a power network. There are several Transmission planning and operation compliance standards pertaining to voltage criterion from NERC and Independent System Operators (ISO) directed toward the utilities to operate their grid within tight voltage limits. This requires the utility to perform comprehensive planning studies of …

Angiography And Monitoring Of Hemodynamic Signals In The Brain Via Optical Coherence Tomography, Alana Mauluidy Soehartono

Theses and Dissertations

The brain is a complex network of interconnected neurons with each cell functioning as a nonlinear processing unit. Neural responses to stimulus can be described by activity in neurons. While blood flow changes have been associated with neural activity and are critical to brain function, this neurovascular coupling is not well understood. This work presents a technique for neurovascular interrogation, combining optogenetics and optical coherence tomography.

Optogenetics is a recently developed neuromodulation technique to control activity in the brain using light with precise spatial neuronal control and high temporal resolution. Using this method, cells act as light-gated ion channels and …

Performance Evaluation Of Multiple Antenna Systems, M-Adib El Effendi

Theses and Dissertations

Wireless traffic is in a continuous increase and there are growing demands for wireless systems that support higher interference suppression and noise mitigation for mobile and cellular communications. Single antenna systems use frequency or time diversity to overcome the multipath fading effect as it represents a major problem that results in sever performance degradation. However, frequency diversity is inefficient in terms of bandwidth requirements and time diversity needs slow time varying channels. Space diversity has been proposed as an alternative to the former schemes where more antennas are added to the transmitter and/or receiver. Nevertheless, when multiple antennas are used; …

High Power Gain Guided Index Antiguided Fiber Lasers And Amplifiers, Parisa Gandomkar Yarandi

Theses and Dissertations

Abstract

Increasing the core size of high-power fiber lasers and amplifiers is highly desired in order to mitigate the unwanted nonlinear optical effects and raise the optical damage threshold. If the core size of conventional index-guided (IG) optical fibers increases, the fiber will become multimode, because it is very difficult to control and fine-tune the index step between the core and cladding to satisfy the single mode condition. Siegman proposed Gain-guided index-antiguided (GG-IAG) fibers as a possible platform for ultra-large-core single-mode operation for lasers and amplifiers.

In this thesis, the beam-quality factor M2 for the fundamental LP₀₁ mode of …

Modeling, Analyses And Assessment Of Microgrids Considering High Renewable Energy Penetration, Qiang Fu

Theses and Dissertations

Microgrids are receiving attention due to the increasing need to integrate distributed generations and to ensure power quality and provide energy surety to the customers. Since renewables need to be in the mix for energy surety, a high renewable-energy penetrated microgrid is analyzed in this paper. The standard IEEE 34 bus distribution feeder is adapted and managed as a microgrid by adding distributed generation and load profiles. The 25kV system parameters are scaled down to 12kV and renewable sources including solar PV and wind turbines, an energy storage system, and a natural gas generator have been added to the 34-bus …

Dc Microgrid Modeling And Energy Storage Placement To Enhance System Stability, Carl Westerby

Theses and Dissertations

The work of this thesis represents a joint venture between the University of Wisconsin-Milwaukee and the University of Wisconsin-Madison. A DC microgrid is selected for the efficiency benefits, lack of reactive power in the system, and ease of connecting to an AC grid. The system modeling relies on physical parameters and industry standard methods for the estimation of loads and lines. An example model is created for the University of Wisconsin - Milwaukee's Campus. Due to the high penetration of renewable energy sources in the example model, system stability is a concern. To help mitigate stability issues, analysis is performed …

Neural Network Based Microgrid Voltage Control, Chun-Ju Huang

Theses and Dissertations

The primary purpose of this study is to improve the voltage profile of Microgrid using the neural network algorithm. Neural networks have been successfully used for character recognition, image compression, and stock market prediction, but there is no directly application related to controlling distributed generations of Microgrid. For this reason the author decided to investigate further applications, with the aim of controlling diesel generator outputs.

Firstly, this thesis examines the neural network algorithm that can be utilized for alleviating voltage issues of Microgrid and presents the results. MATLAT and PSCAD are used for training neural network and simulating the Microgrid …

Voltage Stability Assessment Using P-Q Region Incorporating Wind Power, You Wang

Theses and Dissertations

Voltage stability assessment (VSA) is a significant part in planning and operating of the power system. As one of the classic static VSA method, the P-V curve is widely used in identifying the weak buses in one power system. Normally, there is a required range of bus voltage variation that restricts load with fixed power factor within a maximum value. The loading margin can be defined as the distance between the operating point and the maximum load. The proposed P-Q region, which defines safe region for voltage stability, is more effective and intuitional when applying to VSA compared to the …

Indoor Radio Measurement And Planning For Umts/Hspda With Antennas, Marcellinus Iheanyi Eheduru

Theses and Dissertations

Over the last decade, mobile communication networks have evolved tremendously with a key focus on providing high speed data services in addition to voice. The third generation of mobile networks in the form of Universal Mobile Telecommunications System (UMTS) is already offering revolutionary mobile broadband experience to its users by deploying High Speed Downlink Packet Access (HSDPA) as its packet-data technology. With data speeds up to 14.4 Mbps and ubiquitous mobility, HSDPA is anticipated to become a preferred broadband access medium for end-users via mobile phones, laptops etc. While majority of these end-users are located indoors most of the time, …

Optimal Reactive Power Planning For Distribution Systems Considering Intermittent Wind Power Using Markov Model And Genetic Algorithm, Cheng Li

Theses and Dissertations

Wind farms, photovoltaic arrays, fuel cells, and micro-turbines are all considered to be Distributed Generation (DG). DG is defined as the generation of power which is dispersed throughout a utility's service territory and either connected to the utility's distribution system or isolated in a small grid. This thesis addresses modeling and economic issues pertaining to the optimal reactive power planning for distribution system with wind power generation (WPG) units. Wind farms are inclined to cause reverse power flows and voltage variations due to the random-like outputs of wind turbines. To deal with this kind of problem caused by wide spread …

System For Detection Of Defects In Cables Of Bridge Structures, Emad Ismail Abdel Salam

Theses and Dissertations

Over the last 75 years, many cable-supported bridges have been built in America, Europe, Asia and other parts of the world. However, over the years these bridges have aged and been exposed to environmental conditions such as rain, snow, de-icing and harmful chemicals. These conditions cause various levels of deterioration in bridges, particularly corrosion. Corrosion causes a loss of cross-section in the steel, adversely affecting the bridge's capacity to carry its service loads, and can possibly cause bridge failures. Although many methods have been attempted to inspect these bridges, most have offered limited success. In the recent years, it has …

Scr-Based Wind Energy Conversion Circuitry And Controls For Dc Distributed Wind Farms, Ravi Nanayakkara

Theses and Dissertations

The current state of art for electrical power generated by wind generators are in alternating current (AC). Wind farms distribute this power as 3-phase AC. There are inherent stability issues with AC power distribution. The grid power transfer capacity is limited by the distance and characteristic impedance of the lines. Furthermore, wind generators have to implement complicated, costly, and inefficient back-to-back converters to generate AC. AC distribution does not offer an easy integration of energy storage. To mitigate drawbacks with AC generation and distribution, direct current (DC) generation and high voltage direct current (HVDC) distribution for the wind farms is …

Multi-Level Medium Voltage Inverter For Dc Distributed Wind Farm To Establish Grid Interface And Provide Ancillary Support, Yogesh Popatlal Patel

Theses and Dissertations

Wind energy has gained in popularity in recent years due to cost, security and environmental concerns associated with conventional energy sources like fossil fuels. However, the utilization of wind energy in power systems creates many technical and non-technical challenges that need to be addressed for successful integrations. The main technical issues related to wind energy are its uncertainty and variability and their impacts on stability, reliability and quality of the electric power. In systems with high wind energy penetrations, unlike conventional generations, sudden changes in active and/or reactive power demand cannot be supported by wind energy. This lack of demand …

Dc And Microwave Analysis Of Gallium Arsenide Field-Effect Transistor-Based Nucleic Acid Biosensors, John K. Kimani

Theses and Dissertations

Sensitive high-frequency microwave devices hold great promise for biosensor design. These devices include GaAs field effect transistors (FETs), which can serve as transducers for biochemical reactions, providing a platform for label-free biosensing. In this study, a two-dimensional numerical model of a GaAs FET-based nucleic acid biosensor is proposed and simulated. The electronic band structure, space charge density, and current-voltage relationships of the biosensor device are calculated. The intrinsic small signal parameters for the device are derived from simulated DC characteristics and used to predict AC behavior at high frequencies.

The biosensor model is based on GaAs field-effect device physics, semiconductor …

Novel Methodology To Determine The Optimal Energy Storage Location In A Microgrid To Support Power Stability, Luis Fernando Montoya Sanchez

Theses and Dissertations

This thesis represents the result from a cooperation project, between the University of Wisconsin Milwaukee and Eaton corporation. Here, a new methodology to select the best location for storage in Microgrids is proposed, this methodology is an adaptation of a well known technique commonly used to solve the Power Flow in Power System planning analysis. This technique is known as the fully-coupled Newton Raphson methodology, and it commonly used to solve the power flow study analysis. Due to the large incorporation of renewable energy to distribution and subtransmission systems, the requirement of a method to quantify and select the optimal …

Medical Grade High Frequncy Power Distribution Units, Ezana Mekonnen

Theses and Dissertations

The focus of this thesis is to design, model, build, and test a series resonance converter that uses a high frequency isolation transformer, offering significant reduction in size and cost, for powering a Computed Tomography (CT) scanner. The design increases the power quality for the load by isolating the grid side disturbances, and providing regulated desired voltage. The proposed architecture also allows for an optimized point of integration with an UPS, a regulated DC bus to improve waveform fidelity of x-ray generator, and active monitoring and control of the power architecture. Conventional CT systems use a 60Hz transformer, which not …

A Study Of Nonlinear Approaches To Parallel Magnetic Resonance Imaging, Yuchou Chang

Theses and Dissertations

Magnetic resonance imaging (MRI) has revolutionized radiology in the past four decades by its ability to visualize not only the detailed anatomical structures, but also function and metabolism information. A major limitation with MRI is its low imaging speed, which makes it difficult to image the moving objects. Parallel MRI (pMRI) is an emerging technique to increase the speed of MRI. It acquires the MRI data from multiple coils simultaneously such that fast imaging can be achieved by reducing the amount of data acquired in each coil. Several methods have developed to reconstruct the original image using the reduced data …

Discovery And Correction Of Bias In Precision Landmark Location, Colin Foster

Theses and Dissertations

Precision Landmark Location (PLL) estimation is an integral part of 3D motion tracking. Circular landmark location estimation is one method of PLL. Current methods of estimation lead to systematic errors with a magnitude of up to .02 pixels. Estimation inaccuracies of this magnitude lead to unacceptable errors in depth measurement, the largest source of error. In the scope of this thesis, inadequacies in circular landmark location are uncovered and techniques to correct these errors are analyzed, tested, and demonstrated. Deviations in simulated images are seen to be reduced by a factor of three and the variances of real-world data were …

Lithium-Ion Ultracapacitor Energy Storage Integrated With A Variable Speed Wind Turbine For Improved Power Conversion Control, Goran Mandic

Theses and Dissertations

The energy of wind has been increasingly used for electric power generation worldwide due to its availability and ecologically sustainability. Utilization of wind energy in modern power systems creates many technical and economical challenges that need to be addressed for successful large scale wind energy integration. Variations in wind velocity result in variations of output power produced by wind turbines. Variable power output becomes a challenge as the amount of output power of the wind turbines integrated into power systems increases. Large power variations cause voltage and frequency deviations from nominal values that may lead to activation of relay protective …

Accelerating Mri Data Acquisition Using Parallel Imaging And Compressed Sensing, Haifeng Wang

Theses and Dissertations

Magnetic Resonance Imaging (MRI) scanners are one of important medical instruments, which can achieve more information of soft issues in human body than other medical instruments, such as Ultrasound, Computed Tomography (CT), Single Photon Emission Computed Tomography (SPECT), Positron Emission Tomography (PET), etc. But MRI's scanning is slow for patience of doctors and patients. In this dissertation, the author proposes some methods of parallel imaging and compressed sensing to accelerate MRI data acquisition. Firstly, a method is proposed to improve the conventional GRAPPA using cross-sampled auto-calibration data. This method use cross-sampled auto-calibration data instead of the conventional parallel-sampled auto-calibration data …

Optical Cryoimaging Of Celular Redox In Kidneys From Diabetic Mice, Sepideh Maleki

Theses and Dissertations

Diabetic Nephropathy (DN) is the major single cause of end stage renal diseases (ESRD) in the United States. Diabetes is the third leading fatal disorder after cancer and heart disease. It is affecting 8.3% of the residents of the United States, with a total healthcare cost of $174 billion/yr by 2010.

There currently exists a need for a sensitive and specific diagnosis for temporal detection of oxidative stress (OS) in cellular metabolic levels, which plays an early role in the development of DN. The objective of this research is to use a fluorescence optical imaging technique in order to delineate …