Engineering Commons^™

Modeling Of Sic Power Semiconductor Devices For Switching Converter Applications, Ruiyun Fu

Theses and Dissertations

Thanks to recent progress in SiC technology, SiC JFETs, MOSFETs and Schottky diodes are now commercially available from several manufactories such as Cree, GeneSiC and Infineon. SiC devices hold the promise of faster switching speed compared to Si devices, which can lead to superior converter performance, because the converter can operate at higher switching frequencies with acceptable switching losses, so that passive filter size is reduced. However, the ultimate achievable switching speed is determined not only by internal semiconductor device physics, but also by circuit parasitic elements. Therefore, in order to accurately predict switching losses and actual switching waveforms, including …

Passive Equalizer Topology Analysis For Signal Integrity Applications, Kuo-Lun Yen

Theses and Dissertations

In high-speed, high density PCB bus systems, high frequency signal losses and crosstalk can have great impacts on signal integrity and digital timing, which can distort transmitted signals, worsen eye diagrams, and attenuate signal amplitudes. Also, these impacts make digital signals and their energy smearing over multiple bit positions as known as jitters, and cause the phenomenon of inter-symbol interference (ISI) in digital signal transmissions.

The main objective of this thesis is to analyze and develop efficient topology circuits for compensating bus system high frequency losses by using equalization techniques. The thesis has focused on study of various practical and …

Fault Aware Soft Restart Of An Islanded Microgrid Using An Inverter Coupled Energy Storage System, Asif Anwar

Theses and Dissertations

This research developed a method for autonomous operation of an inverter-coupled energy storage system for safe islanding- re-energization - and reconnection of the facility-island or microgrid to the utility / distribution circuit in a seamless manner in the event of a fault. This enables the energy storage system to function as an autonomous source within the utility power distribution system without the need to re-engineer the existing protection coordination in the distribution system. Fault detection based on voltage measurements from the inverter terminals are used to detect a fault and isolate the energy storage-powered facility with negligible power feed into …

Ultrawideband (Uwb) And Reconfigurable Antennas - New Concepts For Conformal Load Bearing Antenna Structures (Clas), Nicholas Bishop

Theses and Dissertations

Conformal antennas have been increasingly playing an important role in a vast number wireless of communication applications. More specifically, Conformal Load Bearing Antenna Structures (CLAS) have drawn a great deal of interest among researchers and engineers because of their advantages of multiple functionality, e.g. antenna and structure both. The objectives of this thesis are to investigate and design innovative conformal Ultrawideband (UWB) endfire antenna arrays and reconfigurable aperture coupled pixel patch antennas both of which are good candidates for CLAS. First, a broadband VHF-UHF end-fire Yagi-Uda array is proposed for possible air vehicle integration and operation within the 240-465 MHz …

Analysis Of Modulation And Voltage Balancing Strategies For Modular Multilevel Converters, Ryan Blackmon

Theses and Dissertations

Modular multilevel converters are an emerging voltage source converter topology suitable for many applications. The increased utilization of HVDC power transmission solutions has resulted in modular multilevel converters becoming a more common converter type. Other applications include interfacing renewable energy power sources to the grid and motor drives. Modular multilevel converters are beneficial for medium voltage motor drives because the properties of this converter topology, such as low distortion, allow for an efficient motor drive design.

Modular multilevel converters are designed where instead of using 6 IGBTs as in a conventional voltage source converter, numerous low-rated IGBTs are used to …

Dislocation Reduction In Silicon Doped High Aluminum Content Algan Layers For Deep Uv Optoelectronic Devices, Hung-Chi Chen

Theses and Dissertations

III-Nitride based deep ultraviolet (UV) light emitting diodes (LEDs) are prospective candidates to replace the conventional bulky, expensive and environmentally harmful mercury lamp as new UV light sources, used in the applications of water and air purification, germicidal and biomedical instrumentation systems, etc. Due to the lack of native substrates and poor carrier injection, AlGaN-based deep UV LED is suffering from low optical power and low overall efficiency, which prevents the availability of low cost, high efficiency deep UV LED on the market.

This dissertation is focused on improving the efficiency of deep UV LEDs, by improving the base template …

Effects Of N-Type Doping On Algan Material Quality, Devendra Diwan

Theses and Dissertations

The field of group III-nitride semiconductors has seen incredible developments during last couple of decades. They are recognized as the most promising materials for a wide field of optoelectronics and electronic devices. Their bandgap ranges from 6.2 eV for AlN to 0.7 eV for InN, covering a wide spectral range from infrared (1.77 mm) to deep ultraviolet (200 nm). Their direct bandgap makes them useful for fabricating optoelectronic devices such as light emitting diodes (LEDs), laser diodes (LDs), and photodetectors. III-nitride semiconductor materials also possess strong bond strengths and exhibit good structural, chemical and thermal stability. These properties make it …

Polyspectral Signal Analysis Techniques For Condition Based Maintenance Of Helicopter Drive-Train System, Mohammed Ahmed Hassan Mohammed

Theses and Dissertations

For an efficient maintenance of a diverse fleet of air- and rotorcraft, effective condition based maintenance (CBM) must be established based on rotating components monitored vibration signals.

In this dissertation, we present theory and applications of polyspectral signal processing techniques for condition monitoring of critical components in the AH-64D helicopter tail rotor drive train system. Currently available vibration-monitoring tools are mostly built around auto- and cross-power spectral analysis which have limited performance in detecting frequency correlations higher than second order. Studying higher order correlations and their Fourier transforms, higher order spectra, provides more information about the vibration signals which helps …

Impedance Estimation Using Randomized Pulse Width Modulation And Power Converters, William M. Mccoy

Theses and Dissertations

With the adoption of technologies such as alternative energy production, DC power grids, and electric vehicles, the use of high power switching converters has seen a dramatic increase. These power converters serve many rolls such as grid-tied inverters in solar farms, high power charging for electric vehicles, motor drives for industrial applications, and DC links in transmission systems. With the increased prevalence of such devices, it is only natural to attempt to optimize their operation. As with any level of converter, it is desirable to have accurate control over the generated voltages and currents. Often, these controllers implement some form …

Crystal Growth, Characterization And Fabrication Of Cdznte-Based Nuclear Detectors, Ramesh Madhu Krishna

Theses and Dissertations

In today's world, nuclear radiation is seeing more and more use by humanity as time goes on. Nuclear power plants are being built to supply humanity's energy needs, nuclear medical imaging is becoming more popular for diagnosing cancer and other diseases, and control of weapons-grade nuclear materials is becoming more and more important for national security. All of these needs require high-performance nuclear radiation detectors which can accurately measure the type and amount of radiation being used. However, most current radiation detection materials available commercially require extensive cooling, or simply do not function adequately for high-energy gamma-ray emitting nuclear materials …

Iii-V Nitride Micro- And Nano-Scale Cantilevers For Multimodal Sensing Applications, Ehtesham Bin Quddus

Theses and Dissertations

Recent research trends in chemical and biological sensing have been geared toward developing molecular sensor devices that are fast, label free, miniaturized and portable. The performance of these devices can be dramatically improved by utilizing multimodal detection techniques, new materials and micro-/nanofabrication technologies. This is especially true for micro-/nanoscale cantilever sensors, which undergo changes in mechanical or electrical properties upon the specific binding of molecules. To develop the sensor devices with the above attributes, we utilized III-V nitride materials: InN nanowires for realizing nanoscale cantilevers and AlGaN/GaN heterostuctures with or without embedded HFETs, for developing microcantilevers. There are mainly two …

Wireless Pressure Sensor System For Medical Applications, Xuehe Wang

Theses and Dissertations

Telemedicine in the modern era is a rapidly developing industry. In a telemedicine system, sensor is the key elements and play important role in any telemedicine applications, especially implantable sensors. Unlike traditional in vitro sensors, there are some special requirements for them like battery-less, compact, and bio-friendly. Therefore, many researchers in institutes as well as in industry are continually developing implantable sensor and sensor system to fulfill the requirements of medical applications.Nine in one thousand people in the United States are born with congenital heart defects and sixty percent die before one year old. As a result, it will be …

Electromagnetic Modeling Of Gan Varactor Microwave Switches, Yi-Hsuan Yang

Theses and Dissertations

Microwave switches are important components which have been widely used in many microwave systems, such as electronic products, satellites communications, antennas, and radars etc. Traditionally, microwave switches are fabricated using pin diodes or MEMS, Si MOSFETs or GaAs HEMTs. These devices, due to the material limitations are suffering from a low breakdown voltage and are unable to handle high power. III-Nitride based varactor microwave switches provide opportunities for high power microwave devices, due to highly conducting 2D electron gas in the channel and high breakdown electric field.

Designing microwave switches typically involves modeling and simulation using tools such as MATLAB, …

Demonstration And Modeling Of Multi-Bit Resistance Random Access Memory, Albert Chen

Albert B Chen

Although intermediates resistance states are common in resistance random access memory (RRAM), two-way switching among them has not been demonstrated. Using a nanometallic bipolar RRAM, we have illustrated a general scheme for writing/rewriting multi-bit memory using voltage pulses. Stability conditions for accessing intermediate states have also been determined in terms of a state distribution function and the weight of serial load resistance. A multi-bit memory is shown to realize considerable space saving at a modest decrease of switching speed.

Point Of Common Coupling (Pcc) Voltage Control Of A Grid-Connected Solar Photovoltaic (Pv) System, Brian Perera, Philip Ciufo, Sarath Perera

Dr Philip Ciufo

In future low voltage grids, with multiple inverter interfaced sources connected, voltage regulation may become a necessary task. The potential exists for inverter interfaced sources to be deployed to regulate the voltage at the point of common coupling (PCC) of each inverter interfaced sources. The PCC voltage regulation is attainable with inverter interfaced sources by dynamically controlling the amount of reactive power injected to the power distribution grid by individual systems. In the current research, a closed-loop controller is proposed to regulate the PCC voltage of a solar photovoltaic (PV) system that is connected to a single-phase power distribution feeder …