Master of Science, The Ohio State University, 2022, Electrical and Computer Engineering

The electrification of transportation, both for personal and industrial use, has steadily increased across industries. Aviation presents a set of unique challenges for electrification including energy storage. Batteries are heavy and less energy-dense than fossil fuel counterparts leading to the concept of more electric aircraft, where traditionally mechanical systems are replaced with electrical systems. Through improvements in Silicon Carbide (SiC) devices and motor technology, electrification of propulsion is emerging. This paper explores the modeling and high-power testing of a 1 MVA integrated modular motor drive designed for a high power-dense hybrid turbine aircraft. Fault analysis of the system was performed using Simulink to simulate the system response to a suite of faults. High-voltage validation of the power electronics was completed on each switching module. Over current, double-pulse, and inverter testing validated the fundamental design and health of the system. Full volt- age and full current open-loop tests were executed using three-phase load inductors to verify functionality of the power electronics independent from the machine. Full integration of the motor and power electronics was done at the University of Wisconsin. Here, the integrated system was pushed to approximately 20% of its rated power and closed-loop control code was verified. Ongoing testing of the system at the NASA Electric Aircraft Testbed (NEAT) facility will bring the and electronics to their full rated power with the high heat rejection capabilities and high-power loads and supplies.

Committee: Julia Zhang (Advisor); Jin Wang (Advisor) Subjects: Electrical Engineering

Doctor of Philosophy, University of Toledo, 2020, Engineering

This dissertation investigates the propagation of information between models of disparate computational complexity and simulation domains with specific focus on the modeling of wide bandgap semiconductors for power electronics applications. First, analytical physics models and technology computer-aided design numerical physics models are presented. These types of physics models are contrasted by ease of generation and computational complexity. Next, processes generating transient simulations from these models are identified. Mixed-mode simulation and behavioral device models are established as two available options. Of these two, behavioral models are identified as the method producing superior computational performance due to their much-reduced simulation time. A comparison of switching performance for two wide bandgap field-effect transistors manufactured with the same process is next presented. Empirical and simulated switching results demonstrate that available models predict the slew rates reasonably well, but fail to accurately capture ringing frequencies. This is attributed to two primary causes; the modeling tool used for this comparison is incapable of producing a sufficiently high-quality fit to ensure accurate prediction and the devices are sensitive to parasitic values beyond the measurement uncertainty of the characterization hardware. To remedy this, a two-fold approach is necessary. First, a new model must be generated which is more capable of predicting steady-state performance. Second, a characterization procedure must be produced which tunes parameters beyond what is possible with empirical characterization. To the first point, a novel model based on the Curtice model is presented. The novel model adapts the Curtice model by adding gate-bias dependence to model parameters and introducing an exponential smoothing function to account for the gradual transition from linear to saturation exhibited by some wide bandgap field-effect transistors. C (open full item for complete abstract)

Committee: Raghav Khanna (Committee Chair); Ivan Celanovic (Committee Member); Daniel Georgiev (Committee Member); Richard Molyet (Committee Member); Mohammed Niamat (Committee Member) Subjects: Electrical Engineering; Energy; Physics

Doctor of Philosophy, The Ohio State University, 2020, Electrical and Computer Engineering

β-Ga2O3 has recently attracted attention as an ultra-wide bandgap (4.7 eV) semiconductor that can be controllably doped, and grown directly from the melt in single crystal form. The ease of n-type doping with tetravalent cations, a wide variety of bulk single crystal and epitaxial film growth techniques have triggered worldwide interest in β-Ga2O3. The predicted breakdown electric field (6-8 MV/cm) is higher than that of GaN or SiC (~3 MV/cm), which when combined with electron mobility (predicted ~250 cm2/Vs) and electron velocity (1.2×107 cm/s) yields higher figures of merits than SiC and GaN devices. This thesis presents theoretical and experimental investigations of β-Ga2O3 device designs to achieve high-performance RF and power electronics for future applications. The first part of the thesis analyzes the potential device advantages that can be derived from the fundamental β-Ga2O3 material parameters (electron mobility, saturation velocity, and breakdown field). The theoretical β-Ga2O3 device output power density is calculated and compared to GaN HEMTs to find the potential RF applications of β-Ga2O3 devices. The potential of β-Ga2O3 for power devices is also calculated and discussed. Through detailed 2-D device simulation, device design strategies for utilizing the high breakdown field and mitigating low electron mobility effects are proposed. The thesis then focuses on the experimental demonstration and progress on lateral β-Ga2O3 device designs, including (AlGa)2O3/Ga2O3 MODFETs and delta-doped MESFFETs. (AlGa)2O3/Ga2O3 MODFET is one suitable device structure for high-performance β-Ga2O3 electronics because of the 2-D electron gas (2DEG) channel with high electron mobility. The electrical properties of the grown film and the MODFET device characteristics are studied. MBE-grown Ohmic contact is developed for the (AlGa)2O3/Ga2O3 MODFETs to improve their device performance. The high mobility 2DEG channel and low-resistance Ohmic contact enable the direct (open full item for complete abstract)

Committee: Siddharth Rajan (Advisor); Robert Coffie (Committee Member); Steven Ringel (Committee Member); Wu Lu (Committee Member); Xiaoxue Wang (Committee Member) Subjects: Electrical Engineering; Solid State Physics

Doctor of Philosophy, The Ohio State University, 2019, Electrical and Computer Engineering

After 60 years' development, Silicon (Si) devices are approaching their performance limitations set by their own material properties. They have difficulties meeting requirements of future medium and high-voltage applications. Medium-voltage Silicon Carbide (SiC) devices break the constraints of Si devices and are projected to be their successors. However, the research of medium-voltage SiC devices is still at an early stage. Technical challenges hinder their applications. This dissertation aims to study and/or provide solutions to key challenges of applying medium-voltage SiC devices. This work first summarizes the major technical challenges and associated research efforts of applying medium-voltage SiC devices. The summary is based on a survey of recent developments of medium-voltage SiC devices and evaluation results of three device examples. Then this dissertation addresses four technical challenges: gate drive design for medium-voltage SiC devices, auxiliary power supply design for gate drives, partial discharges in motor windings, and reflected waves in motor drives. Designs of gate drives and its auxiliary power supplies are challenging. It is because of the fast switching speed of medium-voltage SiC devices and high insulation requirements in high-voltage systems. This work presents a gate drive and its auxiliary power supply targeting 10 kV SiC MOSFETs. The gate drive features a common-mode transient immunity (CMTI) over 200 kV/µs and an overcurrent protection time within 700 ns. Its power supply has an input voltage of 7 kV and an insulation capability over 10 kV. The gate drive and auxiliary power supply further enable the development of a self-sustained circuit building block, which can serve as one of the sub-modules in high-voltage multilevel converters. The high voltage rating and fast switching speed of medium-voltage SiC devices cause concerns of partial discharges. This work studies the partial discharge in a medium-voltage motor winding. A test (open full item for complete abstract)

Committee: Wang Jin (Advisor); Agarwal Anant (Committee Member); Zhang Julia (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, University of Toledo, 2019, Electrical Engineering

This dissertation investigates the modeling of next generation wide bandgap semiconductors in several domains. The first model developed is of a GaN Schottky diode with a unique AlGaN cap layer. This model is developed using fundamental physical laws and analysis and allows for the characteristics of the diode to be designed by adjusting aspects of the diode's fabrication and structure. The second model is of a lateral GaN HEMT and is developed using TCAD simulation software in order to fit experimental data based on static characteristics. This procedure endeavors to simultaneously fit several output characteristics of the HEMT device to facilitate the applicability and evaluation of the device for power electronics applications. This model is then used to analyze the effects of various substrate material choices on the performance of the GaN HEMT in a switching application. Finally, a link between TCAD models of devices and a circuit simulation platform is demonstrated. This system allows for simulation and testing of devices in complex power electronic systems while maintaining a direct dependence between the system-level performance and the physical parameters of the device. This link between TCAD and circuit simulation is then used to develop an iterative optimization procedure to design a semiconductor device for a particular power electronic application. The work demonstrated here develops procedures to create high-fidelity models of wide bandgap semiconductor devices and enables the purposeful design of devices for their intended application with a high degree of confidence in meeting system requirements. It is through this focusing of device modeling and design, that the rate of technological transfer of next-generation semiconductor devices to power electronics systems can be improved.

Committee: Raghav Khanna Ph.D. (Committee Chair); Mansoor Alam Ph.D. (Committee Member); Rongming Chu Ph.D. (Committee Member); Vijay Devabhaktuni Ph.D. (Committee Member); Daniel Georgiev Ph.D. (Committee Member) Subjects: Electrical Engineering

Master of Science, The Ohio State University, 2018, Electrical and Computer Engineering

The advent of SiC based switch technology has led to high efficiency, low weight power electronics. However, these switches lack the maximum current ratings of their Si predecessors, making them ill-suited for single-switch, high-current applications. Hybrid switches place traditional Si devices in parallel with SiC devices to obtain high efficiency while also maintaining a high current limit. To do so, hybrid switches need to be carefully selected based on the demands of the design, using datasheet values from both switches. Hybrid switches also need a control scheme that can safely and efficiently operate the pair of switches. This control scheme takes advantage of zero voltage switching to control devices with higher switching loss at approximately zero voltage, minimizing switching loss. To protect SiC devices, multiple zones of switching are established based on maximum current ratings of the devices, with the switching scheme changing based on the zone. Various switch pairs are tested for conduction losses, switching losses, and zone 2/ zone 3 control in both a DC-DC converter and a DC-AC inverter. Switch efficiency and power density are calculated based on these values to determine the advantages and disadvantages of using hybrid switches in a specific project.

Committee: Julia Zhang (Advisor); Mahesh Illindala (Committee Member) Subjects: Electrical Engineering; Energy; Engineering

Doctor of Philosophy, Case Western Reserve University, 2014, EECS - Electrical Engineering

This work describes the design and testing of a wireless implantable bladder pressure sensor suitable for chronic implantation in humans. The sensor was designed to fulfill the unmet need for a chronic bladder pressure sensing device in urological fields such as urodynamics for diagnosis and neuromodulation for bladder control. Neuromodulation would particularly benefit from a wireless bladder pressure sensor providing real-time pressure feedback to an implanted stimulator, resulting in greater bladder capacity while using less power. The pressure sensing system consists of an implantable microsystem, an external RF receiver, and a wireless battery charger. The implant is small enough to be cystoscopically implanted within the bladder wall, where it is securely held and shielded from the urine stream, protecting both the device and the patient. The implantable microsystem consists of a custom application-specific integrated circuit (ASIC), pressure transducer, rechargeable battery, and wireless telemetry and recharging antennas. Because the battery capacity is extremely limited, the ASIC was designed using an ultra-low-power methodology in which power is dynamically allocated to instrumentation and telemetry circuits by a power management unit. A low-power regulator and clock oscillator set the minimum current draw at 7.5 µA and instrumentation circuitry is operated at low duty cycles to transmit 100-Hz pressure samples while consuming 74 µA. An adaptive transmission activity detector determines the minimum telemetry rate to limit broadcast of unimportant samples. Measured results indicated that the power management circuits produced an average system current of 16 µA while reducing the number of transmitted samples by more than 95% with typical bladder pressure signals. The wireless telemetry range of the system was measured to be 35 cm with a bit-error-rate of 10-3, and the battery was wirelessly recharged at distances up to 20 cm. A novel biocompatible (open full item for complete abstract)

Committee: Steven Garverick (Advisor); Swarup Bhunia (Committee Co-Chair); Margot Damaser (Committee Member); Pedram Mohseni (Committee Member); Christian Zorman (Committee Member) Subjects: Biomedical Engineering; Electrical Engineering

Master of Science in Engineering, Youngstown State University, 2009, Department of Electrical and Computer Engineering

LED lighting has a promising future in consumer markets. Many researchers have conducted researches to improve the LED driver efficiencies. In this thesis, a computer model of a high efficiency resonant power LED driver is developed. The LED driver circuit is constructed and simulated at 20 kHz to 35 kHz of switching frequencies of the MOSFET. The OrCAD 16.2 is used as simulation software. The computer simulations show that the efficiency of the resonant power LED driver is considerably higher compare to that of conventional LED resistive drivers. The MOSFET used in the LED driver circuit has three different models: MOSFET SPICE level 1, level 3 and commercial MOSFET SPICE model (IRF6668). The output power of the LED driver is controlled by the switching frequencies of the MOSFETs and the simulation results suggest that the power resonant LED driver with commercial MOSFET can achieve up to 90% overall system efficiency.

Committee: Frank X. Li PhD (Advisor); Philip C. Munro PhD (Committee Member); Jalal Jalali PhD (Committee Member) Subjects: Electrical Engineering; Engineering

Master of Science in Engineering (MSEgr), Wright State University, 2011, Electrical Engineering

Current-mode control is the most popular scheme used for the operation of SMPS (Switch Mode Power Supplies). Current-mode control, also known as current-programmed mode or current-injected control is a multi-loop control scheme that has an inner loop and an outer voltage loop. The current loop controls the inductor peak current while the voltage loop controls the output voltage. The inner loop follows a set program by the outer loop. Some of the most popular small-signal models that predict the small-signal characteristics of current-mode control scheme have been analyzed and compared in this thesis. A PWM dc-dc buck converter in CCM(Continuous Conduction Mode) has been chosen to explain the phenomenon of current-mode control in all these models. Small-signal characteristics are generated in MATLAB using the simplified analytical transfer functions. Some of the important small-signal characteristics include the current loop gain, control-to-output gain with the current-loop closed and outer loop open, audio susceptibility, and output impedance. The two most important models in consideration are: 1) Continuous-Time Model and 2) Peak Current-Mode control Model. Despite the fact that both these models predict the instability of current-mode control at a duty ratio of 0.5, these models differ significantly in deriving the expression for the sampling gain. As a result, their small-signal characteristics differ over a wide frequency range. Also, a very less explored average current mode control is compared with the peak-current mode control based on the similar small-signal characteristics.

Committee: Marian Kazimierczuk PhD (Advisor); Marian Kazimierczuk PhD (Committee Chair); Saiyu Ren PhD (Committee Member); Zhang Xiaodang PhD (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2011, Electrical and Computer Engineering

Sliding Mode Control (SMC) has become one of the most attractive control techniques due to its robustness and low sensitivity to disturbances and parameters variations. Due to the binary nature inherited in modern power converters mainly controlled by switches with ON and OFF as the only possible modes of operation, SMC is the logical choice when dealing with such systems. An obstacle in implementing SMC in many such systems is the presence of finite amplitude and frequency oscillation called chattering, or better known as “ripple” to the power electronics community, which are mainly caused by imperfections in switching devices. The level of chattering is found to be proportional to the switching frequency. Recent advancement in the semiconductor industry has lead to production of switching devices that can handle powers of dozen KW at frequencies of hundreds KHz. However, switching comes at a very high price as heat and power dissipation increases with increasing switching frequency. The most promising way to find the trade off between the desired level of frequency and level of heat loss is so-called “harmonic cancellation” principle, which implies replacing one converter by a multi-phase one, consisting of a set of parallel converters with the same admissible ripple frequency. Phase shifts between channels or converters are controlled such that the level of the ripple is reduced considerably after summation of the outputs of the phases. The main objective of this thesis is to provide theoretical treatment of chattering reduction through the use of specially interconnected multiphase power converters. The theory is applied to reduce chattering in the case of sliding mode controlled DC/DC boost and buck converters. This thesis also deals with system's identification and parameters' estimation. In many of the estimation techniques found in the literature, convergence of the estimates is usually proven but the convergence rate can be too low. However, in control sys (open full item for complete abstract)

Committee: Vadim Utkin (Advisor); Longya Xu (Committee Member); Jin Wang (Committee Chair) Subjects: Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2004, Electrical Engineering

This PhD research discusses digital control strategies for three-phase Pulse Width Modulated (PWM) voltage inverters used in Uninterruptible Power Supplies (UPS) for single unit and parallel unit systems. For the single inverter system, this research proposes a novel control strategy which utilizes the perfect Robust Servomechanism Problem (RSP) control theory to allow elimination of specified unwanted voltage harmonics from the output voltages under non-linear load conditions and to achieve fast recovery performance on load transient. This technique is combined with a discrete sliding mode current controller that provides fast current limiting capability needed for overload or short circuit conditions. For the parallel inverter system, a combination of two control methods is proposed: average power control method and droop control method. The average power method is used in order to overcome the sensitivity of load sharing to output voltage/current measurement errors and mismatch wiring impedances between units, while the droop method allows the control to still maintain proper load sharing in the event that inter-unit communication is lost. In addition to this, a harmonic droop scheme for sharing of harmonic content of the load currents is introduced based on the proposed single unit control. Control analysis, experimental and simulation studies, using two parallel three-phase PWM inverters, are presented to show the effectiveness of the proposed control strategies, both for single and parallel inverter systems.

Committee: Ali Keyhani (Advisor) Subjects:

Master of Science, The Ohio State University, 2008, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy in Materials Science and Engineering, Youngstown State University, 2024, Materials Science

Semiconductor materials have played a huge role in advancing today's technology through the electronic and photonic devices ushered in over the years. The advancement has been driven in part by society's growing need for electronic devices capable of handling higher power, higher temperature, and higher frequency. Current research efforts are expanding to ultra-wide bandgap semiconductors such as gallium oxide Ga2O3). The principal goal of this dissertation is to obtain high quality β-Ga2O3 films with controlled conductivity by magnetron sputtering deposition. The specific objectives are the following: To grow β-Ga2O3 films on sapphire substrates (section 5.2) and on native β-Ga2O3 by rf sputtering (section 5.3), to produce doped and undoped β-Ga2O3 films (Section 5.4). Additionally, to grow Lu2O3/ Ga2O3 and B2O3/Ga2O3 alloy films on (-2 0 1) UID or Sn-doped Ga2O3 and Al2O3 substrates to tune Ga2O3 original bandgap (Section 5.5). To obtain microstructural, morphological, compositional, and optical data from XRD, AFM, SEM, EDS, and UV-Vis characterization methods for all the experiments mentioned above. From this data, correlate the effects of the varying parameters for the optimization of the films, to use the developed films to fabricate Schottky barrier diodes and proceed with the electrical characterization of the fabricated devices (section 5.6).

Committee: Tom Oder PhD (Advisor); Clovis Linkous PhD (Committee Member); Constantin Solomon PhD (Committee Member); Michael Crescimanno PhD (Committee Member); Donald Priour PhD (Committee Member) Subjects: Electrical Engineering; Engineering; Experiments; Materials Science; Optics; Physics; Technology

Doctor of Philosophy, University of Akron, 0, Electrical Engineering

DC bus capacitor voltage unbalance in Neutral Point Clamped (NPC) multilevel inverters is an inherent challenge with a severe effect on five and higher-level inverters. Capacitor voltages unbalance depends on type of inverter loading and modulation techniques. Following this, modulation-based (soft) voltage balancing schemes manipulate modulations in accordance to load current conditions, while hardware-based (active) balancing, introduce external circuitry dedicated for voltage balancing. Current soft balancing schemes and modulations with unbalance mitigation for five-level NPC inverters require a high number of switchings, especially at high modulation index operations. Moreover, active balancing techniques come with high components count. This dissertation presents, three parts modulation and hybrid voltage balancing scheme, novel solutions for five-level NPC inverters to address limitations seen in earlier voltage balancing solutions. When implemented together, these solutions offer low switching operation and reduce voltage balancing circuitry. The three parts modulation combines three sub-modulations, which switch into different number of DC links within a switching period. These sub-modulations activate at different reference signal magnitude ranges. Three parts modulation reduces voltage unbalance in comparison to conventional modulation while offering soft balancing opportunities. Furthermore, the modulation offers operation with reduced switching when compared to state of the art carrier-based modulations suited for voltage balancing. To address voltage unbalance associated with the modulation, hybrid balancing scheme is preferred as it maintains inverter operation with low switching characteristics. These behaviors are analytically characterized, and verified using Matlab/SIMULINK simulations and experimental testing for both single-phase and three-phase inverters. The hybrid balancing uses active balancing and soft balancing techniques working togethe (open full item for complete abstract)

Committee: Malik Elbuluk (Advisor); Seungdeog Choi (Committee Co-Chair); Nao Mimoto (Committee Member); Kye-Shin Lee (Committee Member); Dane Quinn (Committee Member); Robert Veillette (Committee Member) Subjects: Electrical Engineering; Engineering

Doctor of Philosophy, The Ohio State University, 2023, Electrical and Computer Engineering

The aviation industry faces a growing imperative to decrease greenhouse gas emissions and transition towards more electric aircraft (MEA) and all-electric aircraft (AEA). One key requirement for a successful transition is increasing the power density and efficiency of onboard power converters. Wide-bandgap (WBG) power switching devices, such as silicon carbide (SiC), present a promising solution due to their high voltage capability and rapid switching speed. However, these devices also pose a challenge as their fast switching speed can adversely affect insulation systems. This dissertation aims to investigate and offer a deeper understanding of, as well as solutions to, the challenges related to partial discharge (PD) in aircraft power wiring under high dv/dt voltage pulses generated by SiC devices. The dissertation begins with an overview of the significant technical challenges related to PD that arise from using SiC device-based variable speed drives (VSD). It then discusses existing studies addressing these challenges and the failure of insulation systems due to PD. The literature review highlights disagreements in current research and the absence of comprehensive investigations into PD behavior caused by high dv/dt square-wave voltage pulses and their impact on the premature failure of insulation systems. Subsequently, the dissertation delves into the challenges associated with the PD phenomenon in aviation wires, explaining the factors that influence PD behavior, accurate PD detection methods, and the extraction of meaningful features to quantify PD intensity. This is followed by an experimental study of PD-induced aging under various conditions to explore the effects of different variables on PD behavior and the failure mechanism of aviation wires. The experimental conditions are chosen to examine voltage rise time, voltage amplitude, ambient pressure, ambient temperature, and the dielectric material of aviation wires. The experimental results reveal (open full item for complete abstract)

Committee: Jin Wang (Advisor); Julia Zhang (Committee Member); Anant Agarwal (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2022, Electrical and Computer Engineering

In recent years, direct current power distribution and DC microgrids have gained popularity for a wide range of applications. However, unlike typical AC systems, DC systems must still deal with technical issues such as fault current management/protection, power flow control, power quality management, and the possibility of system instability. The T-type modular DC circuit breaker (T-Breaker) system utilization is proposed in this dissertation as a solution to some of the power quality problems thanks to its compensation capabilities. Inspired by the series and shunt compensation devices in AC transmission and distribution, the T-Breaker device can be utilized in a similar manner to improve the stability in DC grids. Utilizing its modularity feature allows it to be implemented in high voltage DC networks. Its use of locally integrated energy storage and a high tolerance for signal mismatch during quick network transients makes it a distinguished device. When its ancillary compensation functions (shunt, series and series-shunt) are combined with its current breaking function, it can be an all-in-one device that improves future DC grids. This dissertation starts with an overview of the power quality challenges of DC distribution covering the recently proposed solutions to each challenge. The main focus will be on the stability challenges under bus voltage and load power transients when constant power loads (CPLs) are present in the grid. Applications such as electric vehicles, ships, aircrafts and EV charging station contains power electronic converters (dc/dc, dc/ac) that tightly regulate the load, hence they act as CPLs. Due to CPLs' negative incremental impedance, when they interact with the DC system, they might destabilize the grid. Analysis of DC distribution systems's stability has been performed in preliminary studies, and passive stabilization and source/load converter level control strategies have been proposed to address the instability issue, but not (open full item for complete abstract)

Committee: Jin Wang (Advisor) Subjects: Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2022, Electrical and Computer Engineering

Direct current power distribution and dc microgrids have been gaining momentum in recent years for various applications. However, compared to traditional ac systems, dc systems still need to address technical challenges such as fault current management/protection, power flow control, power quality management, and potential system instability. This dissertation proposes the T-Breaker system seeking to address these issues in an all-in-one device with modular multilevel converter functions. It is characterized by its use of locally integrated energy storage, high scalability, and high tolerance to control signal mismatch during the fast network transients. This is a paradigm shift from traditional solid-state circuit breakers as the proposed T-Breaker not only protects against faults, but can also function as an energy router with unparalleled ancillary functions for dc grids. This dissertation starts with a systematic overview of the remaining challenges of dc distribution covering the existing dc circuit breaker technologies, particularly on solid-state circuit breakers, as well as the needs and current status of compensation in dc networks. Taking inspiration from the series and shunt compensation devices in ac transmission and distribution systems, the T-Breaker system with half-bridge sub-modules is derived from traditional solid-state circuit breakers. The proposed circuit has modular multilevel converter functions with an increased number of active switches but no conduction loss penalty when compared with traditional solutions. The basic operation modes and the circuit analysis are carried out, and the limitations are identified for the half-bridge T-Breaker. In order to improve upon these drawbacks, the full-bridge T-Breaker is proposed, with improved performance in sub-module voltage injection to the line, and lowering of total heat flux for more compact thermal designs. Along with the basic functionalities of both T-Breaker topologies, the series and (open full item for complete abstract)

Committee: Jin Wang (Advisor); Vadim Utkin (Committee Member); Julia Zhang (Committee Member) Subjects: Electrical Engineering

Master of Science, Miami University, 2021, Computational Science and Engineering

Semiconductor switching device parameters change with aging. This degradation reduces power electronics' performance and eventually results in failure of the circuitry. To prevent this from occurring, many researchers have identified precursors to failure. This research presents the damage indicators unique to repetitive, short circuit conditions in different SiC power devices and Si IGBTs. It investigates how the conducted electromagnetic interference (EMI) signature changes with aging, the degrading parameters behind the change and proposes a methodology to determine the fault location. This research also examines using EMI measurements to assess the health of commercially available SiC MOSFETs, SiC cascodes, and Si IGBTs. The devices were aged via repetitive short-circuit events without exceeding the components' critical energy. They are characterized by measuring the change in switching characteristics, EMI signature and device-specific parameters. SiC and Si devices age in different ways under repetitive short-circuit events. The variety of parameter degradations indicates that the devices' fault location is not the same, contributing to different changes in the EMI spectrum. Notable changes were seen in the IGBT's EMI spectrum and SiC devices at a specific frequency range due to device degradation.

Committee: Mark Scott (Advisor); Miao Wang (Committee Member); Chi-Hao Cheng (Committee Member) Subjects: Engineering

Master of Science in Mechanical Engineering (MSME), Wright State University, 2018, Mechanical Engineering

Environmental and safety concerns have necessitated a phase-out of lead-based alloys, which are often used in electronics solder applications. In order to properly assess suitable replacement materials, it is necessary to understand the deformation mechanisms relevant to the application. In the case of electronics solder, creep is an important mechanism that must be considered in the design of reliable devices and systems. In this study, Power-Law and Garofalo constitutive creep models were derived for two medium temperature solder alloys. The first alloy is known by the commercial name Indalloy 236 and is a quaternary alloy of lead, antimony, tin, and silver. The lead-free alternative is a binary alloy of tin and antimony known by the trade name Indalloy 264. Constant strain rate tests were conducted at temperatures from -20 to 175 Celsius using constant strain rate tensile testing in the range of e-5 s-1 to e-1 s-1. Creep constants were defined for use in materials selection and design analysis activities.

Committee: Daniel Young Ph.D. (Advisor); Raghavan Srinivasan Ph.D., P.E. (Committee Member); Joseph Slater Ph.D., P.E. (Committee Member) Subjects: Aerospace Materials; Materials Science; Mechanical Engineering; Mechanics

Doctor of Philosophy, University of Akron, 2018, Electrical Engineering

This dissertation addresses advanced control methodologies for the five-phase permanent magnet assisted synchronous reluctance motor (F-PMa-SynRM) drive under various open phase fault conditions. F-PMa-SynRMs are principally reluctance-type machines which contain fewer magnets than permanent magnet machines. The major advantage of F-PMa-SynRMs is their inherent fault-tolerant capability, which makes them suitable for critical applications in the automotive and aerospace industries. However, under different open phase faults, F-PMa-SynRMs lose their primary advantages due to reduced average torque and higher torque ripple creating severe vibrations that may cause immediate system shutdown. Additionally, the parameter estimation becomes challenging due to the temperature variations and the presence of current harmonics. In these situations, it is essential to develop advanced fault-tolerant control (FTC) methods for F-PMa-SynRMs targeting the maximization of average torque, minimization of torque ripple, and accurate estimation of temperature. Also, during the FTC, a fault detector is necessary to implement any feedback control methods. An optimal phase advance control method is proposed to maximize the reluctance torque with a minimum phase current under different open phase fault coniii ditions. Then, an active torque ripple minimization (TRM) technique adopting three major steps is proposed as follows: (i) active current harmonic identification, (ii) percentile harmonic injection, and (iii) vector rotation of healthy phases. After that, an analytical method is proposed to estimate magnet temperature in the F-PMa-SynRM without needing any temperature sensors. Finally, this dissertation develops a simplified fault detection method based on five-phase symmetrical component (SC) theory. Extensive simulation using MATLAB and finite element method is done to validate the theoretical claims. For further validation, experiments have been conducted on a 2.9 kW F-PMa-S (open full item for complete abstract)

Committee: Seungdeog Choi (Advisor) Subjects: Engineering