Engineering Commons^™

Power System Electromagnetic Transient Simulation Using A Semi-Analytical Approach, Min Xiong

Doctoral Dissertations

This dissertation investigates efficient power system electromagnetic transient (EMT) simulations using a semi-analytical approach.

First, based on state-space equations of system EMT models, a semi-analytical solution (SAS) is acquired using the Differential Transformation Method (DTM). The DTM can efficiently derive the SAS of any linear or nonlinear system as a power series in time in a recursive manner using well-developed transformation rules. A high-order SAS allows a large time step to speed up the simulation while maintaining the same level of accuracy. Also, a variable time step approach is proposed to further improve its efficiency. Case studies on multiple systems …

Static And Dynamic State Estimation Applications In Power Systems Protection And Control Engineering, Ibukunoluwa Olayemi Korede

Doctoral Dissertations

The developed methodologies are proposed to serve as support for control centers and fault analysis engineers. These approaches provide a dependable and effective means of pinpointing and resolving faults, which ultimately enhances power grid reliability. The algorithm uses the Least Absolute Value (LAV) method to estimate the augmented states of the PCB, enabling supervisory monitoring of the system. In addition, the application of statistical analysis based on projection statistics of the system Jacobian as a virtual sensor to detect faults on transmission lines. This approach is particularly valuable for detecting anomalies in transmission line data, such as bad data or …

Fourier Analysis And Optimization Of Inductive Wireless Power Transfer For Electric Vehicle Charging, Andrew P. Foote

Doctoral Dissertations

With the growth of electric vehicle (EV) popularity, different charging options to increase user convenience and reduce charging time such as high power wireless charging are increasingly being developed and researched. Inductive wireless power transfer (WPT) systems for EVs must meet specifications such as stray field, battery power and voltage operating range, efficiency, and ground clearance. The coil geometry and design have a large impact in meeting these constraints. Typical design approaches include iterative analysis of predetermined coil geometries to identify candidates that meet these constraints.

This work instead directly generates WPT coil shapes and magnetic fields to meet specifications …

Refinement And Performance Analysis Of The Stepped Frequency Microwave Radiometer In Extra Tropical Cyclone Conditions, Jezabel Vilardell Sanchez

Doctoral Dissertations

The Stepped Frequency Microwave Radiometer (SFMR) is a key instrument for estimation of ocean surface wind speed and rain rate in tropical and extra-tropical cyclones research. Through the observed brightness temperature (TB) over a range of six C-band frequencies, the SFMR derives these key parameters used by hurricane specialists to issue watches and warnings. The information gathered with this instru- ment is also pivotal for post-storm studies and satellite calibrations. Currently, the SFMR requires an average time of 5-10 seconds of averaging to cycle through the six di↵erent frequency channels, so in regions with strong wind/rain gradients such as the …

Development Of A Soft Robotic Approach For An Intra-Abdominal Wireless Laparoscopic Camera, Hui Liu

Doctoral Dissertations

In Single-Incision Laparoscopic Surgery (SILS), the Magnetic Anchoring and Guidance System (MAGS) arises as a promising technique to provide larger workspaces and field of vision for the laparoscopes, relief space for other instruments, and require fewer incisions. Inspired by MAGS, many concept designs related to fully insertable magnetically driven laparoscopes are developed and tested on the transabdominal operation. However, ignoring the tissue interaction and insertion procedure, most of the designs adopt rigid structures, which not only damage the patients' tissue with excess stress concentration and sliding motion but also require complicated operation for the insertion. Meanwhile, lacking state tracking of …

Reducing The Levelized Cost Of Energy Of Residential Pv Inverters Through Dynamic Hardware Allocation, Kamal Sabi

Doctoral Dissertations

Renewable energy, such as wind and solar are becoming an integral part of world energy production. Photovoltaic (PV) systems are projected to constitute a large portion of the energy generation portfolio. Achieving a low-cost residential PV system will enable the wide adoption of solar energy throughout the USA. Although innovation in several areas is required to achieve this goal of a low-cost residential PV system, inverter reliability innovation is one key area that is essential. Present string inverters' lifetime is less than 15 years. Increasing their lifetime to 50 years will reduce the cost of operation and maintenance, increase energy …

Multiple Objective Co-Optimization Of Switched Reluctance Machine Design And Control, Timothy Burress

Doctoral Dissertations

This dissertation includes a review of various motor types, a motivation for selecting the switched reluctance motor (SRM) as a focus of this work, a review of SRM design and control optimization methods in literature, a proposed co-optimization approach, and empirical evaluations to validate the models and proposed co-optimization methods.

The switched reluctance motor (SRM) was chosen as a focus of research based on its low cost, easy manufacturability, moderate performance and efficiency, and its potential for improvement through advanced design and control optimization. After a review of SRM design and control optimization methods in the literature, it was found …

Security Of Hardware Accelerators In Multi-Tenant Fpga Environments, Shayan Moini

Doctoral Dissertations

Field-programmable gate arrays (FPGAs) play an important role in the acceleration of computationally expensive algorithms for machine learning, aerospace, and ASIC prototyping. The emergence of FPGAs in the cloud (cloud FPGAs) has accelerated FPGA adoption in various applications due to their low initial cost and the ability to quickly prototype a design. Multi-tenancy, in which multiple users execute circuitry in the same FPGAs simultaneously with logical isolation, reduces cloud FPGA usage cost and increases FPGA utilization. Multi-tenancy introduces new security challenges, such as remote side-channel and fault injection attacks, that cannot be addressed with traditional countermeasures against attacks. In this …

Frontiers In The Self-Assembly Of Charged Macromolecules, Khatcher O. Margossian

Doctoral Dissertations

The self-assembly of charged macromolecules forms the basis of all life on earth. From the synthesis and replication of nucleic acids, to the association of DNA to chromatin, to the targeting of RNA to various cellular compartments, to the astonishingly consistent folding of proteins, all life depends on the physics of the organization and dynamics of charged polymers. In this dissertation, I address several of the newest challenges in the assembly of these types of materials. First, I describe the exciting new physics of the complexation between polyzwitterions and polyelectrolytes. These materials open new questions and possibilities within the context …

Analysis And Development Of Multiple Phase Shift Modulation In A Sic-Based Dual Active Bridge Converter, Yu Yan

Doctoral Dissertations

Renewable energy adoption is a popular topic to release the stress of climate change caused by greenhouse gas. Electricity is ideal secondary energy for clean primary energy such as nuclear, wind, photovoltaic, and so on. To extend the application of electricity and reduce fossil energy consumption by transportation sectors, electric vehicles (EVs) become promising technology that can further inspire the development of renewable energy.

Battery as the core in an EV provides the energy to the motor and all on-board electric equipment. The battery charger is mainly composed of a power factor correction (PFC) and isolated DC-DC converter. Therefore, power …

Power Quality Control And Common-Mode Noise Mitigation For Inverters In Electric Vehicles, Yang Huang

Doctoral Dissertations

Inverters are widely utilized in electric vehicle (EV) applications as a major voltage/current source for onboard battery chargers (OBC) and motor drive systems. The inverter performance is critical to the efficiency of EV system energy conversion and electronics system electro-magnetic interference (EMI) design. However, for AC systems, the bandwidth requirement is usually low compared with DC systems, and the control impact on the inverter differential-mode (DM) and common-mode (CM) performance are not well investigated. With the wide-band gap (WBG) device era, the switching capability of power electronics devices drastically improved. The DM/CM impact that was brought by the WBG device-based …

Stability Analysis And Design Of Grid-Interactive Power Electronic Converters, Le Kong

Doctoral Dissertations

The increasing penetration of power electronic converters (PECs) can provide high flexibility, full controllability, sustainability, and improved efficiency for future electric power systems. However, it also introduces new challenges since the wide-frequency-band control dynamics of PECs can interact with the power system and result in different types of instability issues. To holistically address the instability issues, several research activities are conducted in this dissertation.

The modular multilevel converter (MMC), which is one of the most common PECs in high- or medium-voltage power systems, is investigated. An improved MMC dc impedance model is developed by considering both the submodule voltage and …

X-Band Phased-Array Weather-Radar Polarimetry Testbed, William Heberling Iv

Doctoral Dissertations

Phased-array weather radar have potential to replace reflector dish radar in major weather radar networks such as NEXRAD, providing faster update times and greater scan flexibility. However, the use of electronic scanning introduces polarization errors on weather radar measurables, requiring polarimetric bias calibration. The sources of polarimetric bias have been described theoretically, but experimental verification is still limited. Additionally, no standard method of calibration for polarimetric bias exists for phased-arrays. Therefore, the University of Massachusetts Amherst (UMass) presents a fully operational X-Band phased-array weather radar polarimetric testbed. The testbed evaluates the calibration of a planar dual-polarization X-band phased-array radar through …

Systematic Design Of A 100 W 6.78 Mhz Wireless Charging Station Covering Multiple Devices And A Large Charging Area, Jie Li

Doctoral Dissertations

Wireless power transfer (WPT) promises to offer safe and convenient charging in consumer electronics applications. The application ranges from sub-watt medical implant device charging to watt-level household charging, further to the kilowatt electric vehicle (EV) and railway charging. At present, two industry standards are widely used to guide the WPT product design. The Qi standard describes an application that requires the receiver to be placed close to the transmitter, called "tightly coupled" WPT. The receiver coil typically has a similar size compared to the transmitter. And the operation frequency is in the kHz range. The Airfuel standard, on the other …

A Ringamp-Assisted, Output Capacitor-Less Analog Cmos Low-Dropout Voltage Regulator, Jordan Sangid

Doctoral Dissertations

Continued advancements in state-of-the-art integrated circuits have furthered trends toward higher computational performance and increased functionality within smaller circuit area footprints, all while improving power efficiencies to meet the demands of mobile and battery-powered applications. A significant portion of these advancements have been enabled by continued scaling of CMOS technology into smaller process node sizes, facilitating faster digital systems and power optimized computation. However, this scaling has degraded classic analog amplifying circuit structures with reduced voltage headroom and lower device output resistance; and thus, lower available intrinsic gain. This work investigates these trends and their impact for fine-grain Low-Dropout (LDO) …

Data Center Power System Emulation And Gan-Based High-Efficiency Rectifier With Reactive Power Regulation, Jingjing Sun

Doctoral Dissertations

Data centers are indispensable for today's computing and networking society, which has a considerable power consumption and significant impact on power system. Meanwhile, the average energy usage efficiency of data centers is still not high, leading to significant power loss and system cost.

In this dissertation, effective methods are proposed to investigate the data center load characteristics, improve data center power usage efficiency, and reduce the system cost.

First, a dynamic power model of a typical data center ac power system is proposed, which is complete and able to predict the data center's dynamic performance. Also, a converter-based data center …

A High Frequency Wireless Power Transfer System For Electric Vehicle Charging Using Multi-Layer Non-Uniform Self-Resonant Coil, Ruiyang Qin

Doctoral Dissertations

Wireless EV (Electric Vehicle) charging is an emerging technology with rapid development in the past decade. Compared to wired EV chargers, wireless power transfer (WPT) enables safe and unobtrusive charging for EVs.

This work proposes high frequency wireless charging using a self-resonant (SR) coil at several megahertz. A multi-layer self-resonant coil structure is proposed, allowing high quality factor coils to be fabricated from layers of inexpensive copper foil and dielectric film. Additionally, the self-resonant coil utilizes its interlayer capacitance for resonance, eliminating the external compensation capacitor and shrinking the overall volume of passive component to increase the power density. Comparing …

Silicon Germanium Bicmos Integrated Circuits For Scalable Cryogenic Sensing Applications, Mohsen Hosseini

Doctoral Dissertations

This dissertation is focused on an investigation of BiCMOS cryogenic low noise amplifiers (LNAs) based on Silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) for simultaneous low noise and low power design and also taking advantage of CMOS circuitry for adding flexibility to the LNA design. Cryogenic LNAs' scalability challenges are discussed and addressed in the dissertation. To achieve that, first, HBTs of three state-of-the-art technologies are characterized and modeled at cryogenic temperature. It is shown that SiGe HBT provides a promising compromise of noise temperature, power consumption, and bandwidth. Moreover, a scalable on-chip approach is proposed and verified for biasing of …

Modeling And Control Of A 7-Level Switched Capacitor Rectifier For Wireless Power Transfer Systems, Spencer Cochran

Doctoral Dissertations

Wireless power continues to increase in popularity for consumer device charging. Rectifier characteristics like efficiency, compactness, impedance tunability, and harmonic content make the multi-level switched capacitor rectifier (MSC) an exceptional candidate for modern WPT systems. The MSC shares the voltage conversion characteristics of a post-rectification buck-boost topology, reduces waveform distortion via its multi-level modulation scheme, demonstrates tank tunability via the phase control inherent to actively switched rectifiers, and accomplishes all this without a bulky filter inductor. In this work, the MSC WPT system operation is explained, and a loss model is constructed. A prototype system is used to validate the …

Modeling, Measurement And Mitigation Of Fast Switching Issues In Voltage Source Inverters, Wen Zhang

Doctoral Dissertations

Wide-bandgap devices are enjoying wider adoption across the power electronics industry for their superior properties and the resulting opportunities for higher efficiency and power density. However, various issues arise due to the faster switching speed, including switching transient voltage overshoot, unstable oscillation, gate driving and evaluation difficulty, measurement and monitoring challenge, and potential load insulation degradation. This dissertation first sets out to model and understand the switching transient voltage overshoots. Unique oscillation patterns and features of the turn-on and turn-off overvoltage are discovered and analyzed, which provides new insights into the switching transient. During the experimental characterization, a new unstable …

Impact And Application Of Real-Time Control On Stormwater Systems, Aaron A. Akin

Doctoral Dissertations

Stormwater control measures (SCMs) such as dry extended detention basins and wet ponds are common practices implemented by engineers and designers to mitigate the impact of stormwater runoff. These practices are designed based on historical rainfall data to attenuate runoff to pre-development conditions and, once they are installed, are unable to adapt to changing rainfall patterns or watershed restoration objectives. To solve these climate resiliency issues, several studies were conducted which investigated the impact of retrofitting such systems with a controllable outlet to increase or change detention times during rainfall events along with the novel instrumentation and methodologies necessary for …

Thermoelectric Transport In Disordered Organic And Inorganic Semiconductors, Meenakshi Upadhyaya

Doctoral Dissertations

The need for alternative energy sources has led to extensive research on optimizing the conversion efficiency of thermoelectric (TE) materials. TE efficiency is governed by figure-of-merit (ZT) and it has been an enormously challenging task to increase ZT > 1 despite decades of research due to the interdependence of material properties. Most doped inorganic semiconductors have a high electrical conductivity and moderate Seebeck coefficient, but ZT is still limited by their high lattice thermal conductivity. One approach to address this problem is to decrease thermal conductivity by means of alloying and nanostructuring, another is to consider materials with an inherently low …

Electro-Thermal Transport In Two-Dimensional Materials And Their Heterostructures, Arnab K. Majee

Doctoral Dissertations

”Smaller is better” is the mantra that has driven semiconductor industry for the past 50 years. The on-going quest for faster electronic switching, higher transistor density, and better device performance, has been driven by a self-fulfilling prophecy popularly known as Moore’s law, according to which the number of transistors per unit area of a chip doubles itself approximately every two years. A modern smartphone has about 8 billion transistors, which is as large as current earth’s population. Although each transistor dissipates negligible power, but the collective power dissipation from all the transistors in an electronic gadget and inefficient heat removing …

Addressing Security Challenges In Embedded Systems And Multi-Tenant Fpgas, Georgios Provelengios

Doctoral Dissertations

Embedded systems and field-programmable gate arrays (FPGAs) have become crucial parts of the infrastructure that supports our modern technological world. Given the multitude of threats that are present, the need for secure computing systems is undeniably greater than ever. Embedded systems and FPGAs are governed by characteristics that create unique security challenges and vulnerabilities. Despite their array of uses, embedded systems are often built with modest microprocessors that do not support the conventional security solutions used by workstations, such as virus scanners. In the first part of this dissertation, a microprocessor defense mechanism that uses a hardware monitor to protect …

Design And Implementation Of An Isfet Sensor With Integration Of An On-Chip Processor, Shaghayegh Aslanzadeh

Doctoral Dissertations

Portable sensors are used in many applications. Among them, pH sensors are suitable for quantifying and identifying various analytes in real-time and doing so non-invasively. The analytes may have environmental impact such as in water quality monitoring. The analytes may also have biological impact such as monitoring cell culture or remote patient health assessment. CMOS based sensors are compact and enable low power consumption suitable for these portable applications.

This work reports on the development of a portable CMOS based pH sensor. The contributions of this dissertation are as follows. First, a differential pH sensor, with two different sized electrodes …

Design And Implementation Of A Multi-Modal Sensor With On-Chip Security, Ava Hedayatipour

Doctoral Dissertations

With the advancement of technology, wearable devices for fitness tracking, patient monitoring, diagnosis, and disease prevention are finding ways to be woven into modern world reality. CMOS sensors are known to be compact, with low power consumption, making them an inseparable part of wireless medical applications and Internet of Things (IoT). Digital/semi-digital output, by the translation of transmitting data into the frequency domain, takes advantages of both the analog and digital world. However, one of the most critical measures of communication, security, is ignored and not considered for fabrication of an integrated chip. With the advancement of Moore's law and …

Modeling And Optimization Algorithm For Sic-Based Three-Phase Motor Drive System, Ren Ren

Doctoral Dissertations

More electric aircraft (MEA) and electrified aircraft propulsion (EAP) becomes the important topics in the area of transportation electrifications, expecting remarkable environmental and economic benefits. However, they bring the urgent challenges for the power electronics design since the new power architecture in the electrified aircraft requires many benchmark designs and comparisons. Also, a large number of power electronics converter designs with different specifications and system-level configurations need to be conducted in MEA and EAP, which demands huge design efforts and costs. Moreover, the long debugging and testing process increases the time to market because of gaps between the paper design …

Time-Difference Circuits: Methodology, Design, And Digital Realization, Shuo Li

Doctoral Dissertations

This thesis presents innovations for a special class of circuits called Time Difference (TD) circuits. We introduce a signal processing methodology with TD signals that alters the target signal from a magnitude perspective to time interval between two time events and systematically organizes the primary TD functions abstracted from existing TD circuits and systems. The TD circuits draw attention from a broad range of application fields. In addition, highly evolved complementary metal-oxide-semiconductor (CMOS) technology suffers from various problems related to voltage and current amplitude signal processing methods. Compared to traditional analog and digital circuits, TD circuits bring several compelling features: …

A Discrete-Time Technique For Linearity Enhancement Of Wideband Receivers, Mohammad Ghadiri Sadrabadi

Doctoral Dissertations

A new signal processing technique is introduced to enhance the linearity performance of wideband radio frequency (RF) receivers. The proposed technique combines the advancements in mixer first architectures with a library of binary sequences as local oscillator signals to enable wide instantaneous bandwidth and high linearity for the RF receiver. To do so, N-bit pseudo-random-binary-sequences (PRBS) are used as local oscillator signals. The RF input signal is multiplied with the PRBS at the mixer and then averaged over the full sequence. This in effect reduces the amplitude of the signal and improves the overall linearity of the system. In order …

Silicon-Germanium Heterojunction Bipolar Transistors For Large-Scale Low-Power Cryogenic Sensing Systems, Shirin Montazeri

Doctoral Dissertations

Cryogenic low noise amplifiers (LNAs) are one of the key components in many emerging applications such as radio astronomy or quantum computing in which a weak incoming signal needs to be read out. There have been extensive studies on the feasibility of leveraging silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) to implement cryogenic LNAs in the past. The deployment of such LNAs in the future large-scale systems in radio astronomy or quantum computing is contingent upon the possibility of developing LNAs with reduced DC power dissipation to enable the cooling of a large number of array elements inside a cryogenic cooler. …