Doctor of Philosophy, University of Akron, 2017, Electrical Engineering

Multilevel converters (MLC) have been widely accepted in recent times for high power and medium to high voltage applications. Developments in semiconductor technology and commercial availability of high power switches have made two-level voltage-source converters (VSC) feasible for high power applications; however, for high voltage and high power systems, instead of using switches with high voltage ratings, it is beneficial to connect multiple low-voltage rated switches in series in multilevel approach. Compared to conventional two-level VSCs, MLCs have better capability to (i) lower harmonic distortion of the AC-side waveforms, (ii) decrease the dv/dt switching stresses, and (iii) reduce the switching losses. Moreover, MLCs are easily configurable with multiple renewable energy sources such as solar power, wind power, and fuel cells. Among diverse MLC topologies, diode-clamped converter (DCC) configuration is analyzed in this dissertation. The salient feature of DCC topology is that all three phases of the converter share a common DC bus voltage which minimizes total capacitor requirements. However, DCCs have their own limitations such as the voltage balancing among the converter cells and control complexity. Due to the series connection of the dc-capacitor cells, the voltage sharing among the cells deteriorates during certain operating conditions. To have increased number of voltage levels at the output, DCCs require a higher number of power semiconductor switches and associated electronic components. That means multilevel DCCs are more difficult to control and more expensive than two-level VSCs. There is also a much higher possibility of a device failing. To improve the reliability and performance stability of the overall converter system, an easily configurable controller with a fault-tolerant capability is essential. This dissertation presents the development of generalized control algorithms and a novel converter topology to address the inherent technical (open full item for complete abstract)

Committee: Yilmaz Sozer (Advisor); Malik Elbuluk (Committee Member); Seungdeog Choi (Committee Member); Ping Yi (Committee Member); Kevin Kreider (Committee Member) Subjects: Electrical Engineering

Master of Science in Engineering, Youngstown State University, 2024, Department of Electrical and Computer Engineering

With technological advancements in the field of wide bandgap semiconductors, the role of (Gallium Nitride) GaN transistors has been contributing significantly to the aspects of higher switching frequency operation with lower switching losses, thereby increasing the efficiency of the device. The study of GaN HEMT devices, due to their higher switching frequency and high-performance semiconducting properties, is a huge topic of interest within the power electronics community, which is why the need for its academic study and research is significant. The CoolGaN™ ™ 600V HEMT half-bridge evaluation board used for this paper is manufactured by Infineon Technologies, featuring a high voltage gate driver IC and up to MHz's range of switching frequency. The Infineon CoolGaN™ 600V HEMT half-bridge evaluation platform is studied for its switching behavior. The GaN device is utilized to explore motor drive applications at different frequency switching conditions, ranging from 50 kHz up to 1MHz. The high-frequency PWM signals are programmed and generated using an Artrix-7 FPGA. An SPWM scheme of control signal generation is digitally implemented in the FPGA. The generated PWM signals from the FPGA are used as the switching gate signal for an and to drive a three-phase gallium nitride inverter with balanced resistive and inductive loads. The output phase voltage and phase current waveforms are monitored and analyzed for their behavior and power factor. The research in this thesis investigates the consequences of employing GaN transistors for high frequency switching in motor drive applications through a combination of studies, simulations, and experiments. This investigation holds significant importance within the realm of industrial power electronics, as it aims to advance efficiency, compactness, and cost-effectiveness across diverse applications.

Committee: Frank Li PhD (Advisor); Vamsi Borra PhD (Committee Member); Pedro Cortes PhD (Committee Member) Subjects: Electrical Engineering

Master of Science in Engineering, Youngstown State University, 2023, Department of Electrical and Computer Engineering

The surging electric vehicle (EV) industry is driving a growing demand for high-performance motor drives as the motor drive systems play a crucial role in an EV's performance and efficiency. Choice of techniques for DC-AC conversion is instrumental in the performance of Voltage Source Inverters (VSI). In this study, a Field Programmable Gate Array (FPGA)-based PWM (Pulse Width Modulation) architecture is proposed for a VSI topology. A variable frequency and soft-starting PWM architecture is proposed for a three-phase induction motor drive. The proposed architecture allows the implementation of Sinusoidal PWM (SPWM) and Space vector PWM (SVPWM) for the control of a three-phase induction motor (TPIM). In this thesis, line-current and phase-voltage characteristics of the TPIM are studied under diferent operating conditions. Simulink is used for the simulation and verifcation of the proposed architecture and experimental results are validated using four-pole squirrel cage TPIM. Harmonic contents for SPWM and SVPWM are studied and superiority of the SVPWM, which can be implemented using the same architecture, is established. Greater DC bus utilization and lower harmonics in SVPWM leads to better performance in terms of power conversion efficiency compared to SPWM. The proposed architecture utilizes a small fraction of the FPGA resources and can be easily integrated into a larger control system architecture. In addition, a PWM generator is designed for high frequency inverters used in wireless inductive power transfer (IPT) applications and is experimentally verifed.

Committee: Frank Li PhD (Advisor); Vamsi Borra PhD (Committee Member); Ghassan Salim PE (Committee Member) Subjects: Electrical Engineering

Master of Science in Engineering, Youngstown State University, 2012, Department of Electrical and Computer Engineering

Two different three-phase inverters are introduced and compared showing the differences and similarities between them in terms of output power, implementation, challenges and efficiency. Both inverters use the same feedback controller and both have the same input voltage and the same load levels. The first inverter is a three-phase sinusoidal pulse width modulation (PWM) inverter that generates gate-control signals using a sinusoidal wave source. It is shown that pulse width modulation utilizes a simpler approach to convert DC power into AC. The second inverter is a three-phase space vector pulse width modulation (SVPWM) inverter. SVPWM inverters utilize a space vector (reference vector) to create the desired sinusoidal waves. SVPWM proved to have less total harmonic distortion (THD% = 1.15%) and faster response time (114ms) with an output error of 0.13V. this compares with a sinusoidal PWM (THD% = 3.73%, response time = 136ms and output error = 0.23V). SVPWM proves to have better overall performance. MATLAB's Simulink is used to build and test the performances of each inverter and then compare the inverters with a pre-existing three-phase grid.

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