Master of Science in Electrical Engineering (MSEE), Wright State University, 2020, Electrical Engineering

The purpose of this thesis is to develop the theory for analysing and designing the non-isolated and isolated type of SEPIC converters for continuous conduction mode (CCM). The non-isolated converter has single output. The isolated converter considered has two cases: single output and multi-output. The principle of operation of each circuit is explained during different time intervals of the switching cycle. The analytical expressions for various characteristics of the circuits are derived, such as: MV DC and MIDC of the lossless and lossy converter; average and peak-to-peak currents through the inductors, primary and secondary windings of the transformer; average and peak-to-peak voltages across the capacitors; boundary conditions between CCM and DCM; minimum inductance of the inductors and magnetizing inductance of the transformer and minimum capacitances of the capacitors to operate the converter in CCM; power losses of all the components and efficiency of the converter. The converters analyzed are supported by a design example and also simulated using Saber software. The simulation results for each circuit are in good agreement with the theoretically calculated values for an assumed specifications of the converter. For instance, the respective η(theoretical), η(assumed), and η(simulated) of the non-isolated, single output and multi-output isolated converters are 89.84%, 90%, and 91.448%; 87.54%, 90%, and 90.076%; and 86.78%, 90%, and 87.76%.

Committee: Marian K. Kazimierczuk Ph.D. (Advisor); Saiyu Ren Ph.D. (Committee Member); Yan Zhuang Ph.D. (Committee Member) Subjects: Electrical Engineering

Master of Science, University of Toledo, 2014, Electrical Engineering

A multilevel DC-DC converter converts a DC source from one voltage level to another level. DC-DC converters are important in portable devices like cell phones, laptops, etc, as well as in applications such as electric vehicles, which have subcircuits operating at voltages different from the supply voltage. In this thesis, two new multilevel DC-DC converter system modules: one-to-many topology and cascaded topology are presented. Comparisons are made for the proposed multilevel DC-DC converter systems along with the existing multilevel DC-DC converter system. The comparisons are made in the terms of range of the output voltage, maximum output voltage, number of steps of output voltages, number of switches operated for any given output voltage, and the ripples in the output voltage. Among all the proposed converter system topologies, cascaded topology with even number of modules turned out to be more efficient in terms of maximum output voltage and number of steps of output voltages. Two new different multilevel DC-DC converter modules are presented in this thesis. However only one of them facilitates the implementation of cascaded topology of DC-DC converters and decrease the transition currents, while other just decrease the transition currents. Comparisons are based on different losses during the circuit operation, ripple voltages, and efficiency. One of the proposed converter modules limits the transient currents signficantly over existing converters during the output voltage transition in multilevel DC-DC converter topologies for a given transition time. Though the efficiencies of the proposed modules are slightly less (< 1%) than the existing converter modules they facilitate the implementation of cascading converters. Also the reduction in the transition currents can potentially increase the life of the converter modules.

Committee: Vijay Devabhaktuni (Committee Chair); Srinivasa Vemuru (Committee Co-Chair); Niamat Mohammed (Committee Member) Subjects: Electrical Engineering

Master of Science in Electrical Engineering (MSEE), Wright State University, 2018, Electrical Engineering

Advancements in Direct Current (DC) electrical power systems have enabled new functionality in many, varied applications. Discrete power semiconductor devices are increasing in efficiency, switching frequency, and power density, resulting in greater usage of DC power management and distribution methods, including DC/DC conversion. DC distribution lacks inherent capability to safely and effectively break fault current, particularly in mobile solutions, where larger and slower electromechanical switching devices are not optimal or feasible. One solution is to design a low-energy breaking point into a switching power supply. Simpler converter designs, with a lower number of switching devices, have been modeled and can be functionally utilized for this purpose. However, these designs cannot easily or efficiently provide isolation between the source and the load. A full-bridge DC/DC converter can accomplish this task with galvanic isolation through a transformer. The full-bridge DC/DC converter is fairly complex to analyze with state-space analysis and does not have an existing averaged model. This thesis focuses on developing averaged and small-signal models for the full-bridge DC/DC converter; validating the small-signal averaged models by simulation in SABER circuit simulation software; and using the validated models to design a full-bridge DC/DC converter for simulation in SABER. The converter power stage is designed along with a Type II controller, a comparative current limit, non-Zero-Voltage-Switching gate drives, and a synchronous rectifier. The designed converter is evaluated for closed-loop stability against step changes in input voltage, load current, and reference voltage. The results are provided to show sufficient response of the full-bridge DC/DC converter, given the design parameters. The proposed architecture accommodates future work to reduce DC fault let-through energy.

Committee: Marian Kazimierczuk Ph.D. (Advisor); Ray Siferd Ph.D. (Committee Member); LaVern Starman Ph.D. (Committee Member) Subjects: Electrical Engineering

Master of Science in Electrical Engineering (MSEE), Wright State University, 2019, Electrical Engineering

The student's employer is in need of a three phase power supply which can supply a 400Hz signal at +/- 28V at 2A. The input to the power supply is +24VDC at an unspecified current. The student's solution is a configurable frequency and voltage power supply. The student chose to utilize a full bridge DC to DC converter topology. A microcontroller was used for supplying pulse width modulated waveforms, performing analog to digital conversions, and controlling a digital to analog converter. The circuit was modeled using Matlab and tested after being manufactured to confirm proper functionality. The configurable three phase power supply worked as intended. Possible improvements to the design include fixing schematic and printed circuit board errors.

Committee: Marian Kazimierczuk Ph.D. (Advisor); Yan Zhuang Ph.D. (Committee Member); Saiyu Ren Ph.D. (Committee Member) Subjects: Electrical 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, 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

Doctor of Philosophy, University of Akron, 2016, Electrical Engineering

The prospective spread of Electric vehicles (EV) and plug-in hybrid electric vehicles (PHEV) arises the need for fast charging rates. Higher charging rates requirements lead to high power demands, which can't be always supported by the grid. Thus, the use of on-site sources alongside the electrical grid for EVs charging is a rising area of interest. In this dissertation, a photovoltaic (PV) source is used to support the high power EVs charging. However, the PV output power has an intermittent nature that is dependable on the weather conditions. Thus, battery storage are combined with the PV in a grid tied system, providing a steady source for on-site EVs use in a renewable energy based fast charging station. Verily, renewable energy based fast charging stations should be cost effective, efficient, and reliable to increase the penetration of EVs in the automotive market. Thus, this Dissertation proposes a novel power flow management topology that aims on decreasing the running cost along with innovative hardware solutions and control structures for the developed architecture. The developed power flow management topology operates the hybrid system at the minimum operating cost while extending the battery lifetime. An optimization problem is formulated and two stages of optimization, i.e online and offline stages, are adopted to optimize the batteries state of charge (SOC) scheduling and continuously compensate for the forecasting errors. The proposed power flow management topology is validated and tested with two metering systems, i.e unified and dual metering systems. The results suggested that minimal power flow is anticipated from the battery storage to the grid in the dual metering system. Thus, the power electronic interfacing system is designed accordingly. Interconnecting bi-directional DC/DC converters are analyzed, and a cascaded buck boost (CBB) converter is chosen and tested under 80 kW power flow rates. The need to perform power factor correction (PF (open full item for complete abstract)

Committee: Yilmaz Sozer Dr. (Committee Chair); Malik Elbuluk Dr. (Committee Member); Seungdeog Choi Dr. (Committee Member); Ping Yi Dr. (Committee Member); Kevin Kreider Dr. (Committee Member) Subjects: Electrical Engineering; Energy

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

Committee: Not Provided (Other) Subjects:

Master of Science in Electrical Engineering, University of Dayton, 2024, Electrical Engineering

This paper presents two DC-DC converters optimized for data center applications, focusing on the 48V DC bus input to low voltage outputs. The first converter discussed is a 48V to 3.2V (15x) MASC DC-DC Converter, which incorporates a high voltage side structure similar to that of a Switched Tank Converter (STC) and a low voltage side utilizing a current doubler circuit comparable to the secondary side of an LLC converter. This innovative design is aimed at minimizing both transformer winding losses and conduction losses on the low voltage side. The reconfigured structure allows for a theoretical reduction of the transformer's winding loss by 44.9% compared to conventional LLC converters, assuming the same core size. Additionally, the conduction loss on the low voltage side devices is reduced by half when compared to traditional STC designs. The experimental results of prototype achieved maximum efficiency of 98.75%. The second converter introduced a 48V to 3.3V Matrix Autotransformer Switched Capacitor DC-DC Converter with Partial Power Processing Regulator. It combines the circuit called matrix autotransformer switched capacitor converter (MASC) with buck converter input in series and output in parallel to achieve regulation purpose. The MASC can work at DCX mode to realize higher efficiency, and only 17.9% of the total power are processed by buck converter for regulation purpose. In this way, the power loss is reduced and the overall performance of the prototype is improved. A hardware prototype is designed and built. Simulation and experimental results are provided to verify and demonstrate the performance of the MASC with buck regulator converter. The prototype maximum measured efficiency can reach 96.2%.

Committee: Dong Cao (Committee Chair); Bradley Ratliff (Committee Member); Jitendra Kumar (Committee Member) Subjects: Electrical Engineering; Engineering

Master of Science in Electrical Engineering, University of Dayton, 2023, Engineering

Datacenter usage tends to increase as artificial intelligence (AI) grows and becomes more prevalent. High-power density and high efficiency power converters function as intermediate bus converters are required to increase the whole system efficiency for datacenter applications. This thesis presents solutions for intermediate bus converters and the second stage including a 9-times and a 22-times conversion ratio matrix autotransformer switched-capacitor DC-DC converter (MASC) and a detailed design of the 6V-1.5V interleaved buck converter as second stage for 48V dc bus data center applications. MASC has both advantages of switched tank converter and LLC converter. The high voltage side of MASC takes advantage of switched tank converter. The low voltage side of the MASC leveraged a new magnetic integrated autotransformer design that is like a current doubler rectifier in an LLC converter. Compared with the switched tank converter, MASC needs less switches on the low voltage rectifier side to achieve the same conversion ratio. All switches can achieve zero current switching and zero voltage switching. Thus, total power loss is reduced compared with switch tank converter. Compared with LLC converter, the use of matrix autotransformer further reduces the power loss of MASC by removing primary side winding. The optimum die area (phases) of traditional interleaved buck converter and series-capacitor interleaved is analyzed and their efficiency is compared. A 48V-5.33V MASC hardware prototype with a peak efficiency of 98.54%, a full load efficiency of 95.6%, and 654W/in3 power density is designed, built, and tested. A 22x MASC is simulated and the PCB layout is in process.

Committee: Dong Cao (Committee Chair); Bradley Ratliff (Committee Member); Raul Ordonez (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2023, Electrical Engineering

Power electronics devices usage is increasing with the fast development of semiconductor technology. From renewable energy areas to transportation applications, power converters are widely used to achieve power conversion. Thus, the power converter efficiency is important since the large amount of power usage in these applications. Besides, the power density is another key parameter for the power converters due to the concern of the converter size. In this work, the improvement of converter efficiency and density are achieved by adopting new converter topology and using the wide band gap semiconductor devices such as GaN and SiC. Also, the resonant converter performance evaluation method is proposed. Firstly, a new switched-tank modular (STM) topology with zero voltage switching (ZVS) capability is developed. Secondly, a new method helps compare and analysis different topologies is proposed. Finally, a converter for power process in fuel cell based electric drone is designed using the GaN device.

Committee: Dong Cao Dr. (Committee Chair); Feng Ye Dr. (Committee Member); Jitendra Kumar Dr. (Committee Member); Raul Ordonez Dr. (Committee Member) Subjects: Electrical Engineering; 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

Silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors (MOSFETs) greater than 1.2 kV are attractive for medium-voltage (MV) power systems. Compared to traditional silicon (Si) based systems, designs utilizing SiC devices have shown improved performance. Due to improvements in SiC technology, there has been a great investment in the research and development of SiC devices, allowing for an increase in marketshare. Today, SiC MOSFETs have already become more readily available from many device manufacturers. The ruggedness of these devices against short-circuit (SC) events is becoming one of the major concerns for market acceptance. During a SC event, the device is stressed simultaneously with high drain-source voltage and high current, leading to adiabatic heating. This could result in device failure, thus compromising system operation. Industry and transportation applications require switching devices to sustain a considerable SC time to ensure reliable protection. Therefore, it is critical to characterize the SiC devices' SC withstand time (SCWT), SC-induced degradation, and failure mechanisms. As these devices are being applied in MVDC systems, advantages like high power density and efficiency can be achieved. Circuit topologies of isolated high voltage-stepdown ratio dc/dc converters are studied. Among them, the square-wave modular multilevel converter (MMC) based topologies can have high operational flexibility to achieve voltage-step-down and frequency multiplication functions, which have significant implications for designs and applications. In a case study focusing on a 250-kW, 7-kV, MVDC energy storage system designed for improved grid resiliency, comparisons of numerical results are conducted among the MMC-based topologies. A scaled-down 10-kW prototype is presented later. The circuit parameters and failure modes are analyzed, and the design guidelines of the hardware components are introduced. This MV and medium-frequency (MF) conv (open full item for complete abstract)

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

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

This report mainly shows a detailed analysis of the failure mode of the modular multilevel converter (MMC) – based dc/dc converter with a high step-down ratio. Firstly, a basic operation principle and the characteristics of the MMC-DAB circuit are introduced, and a Simulink-based simulation in a normal operation mode is presented. The simulation circuit is based on a 10 kW, 7kV-to-320V circuit. The corresponding test setup and experiment results are included. Secondly, failure modes on the MVDC side will be analyzed and simulated. The failure reason will mainly focus on the open-circuit and short-circuit fault on the bus bar/dc-link capacitor and the upper and lower switch devices of submodules. Furthermore, fiber-optic drop-off cases are considered as well. Then, the LVDC side and the transformer part will be analyzed. It also contains the open-circuit and short-circuit faults and the fiber-optic drop-off cases. After that, the fault detection control and reconfiguration are summarized. One possible fault detection control and reconfiguration of one conditional safety case is simulated. At last, the severity of each case is discussed and ranked to estimate how the fault would affect the whole circuit, which can be clarified as unsafety cases, conditional safety cases, and safety cases. The severity factor includes the fault development time and the detectability. Additionally, targeting the detectable cases, detection methods, and possible software (FPGA/DSP) responses or hardware responses are explored.

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

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

With the continuous drop in the HV battery cost, Electric Vehicles are forecasted to become increasingly affordable. However, with more services being added to electric vehicles, the onboard system complexity and cost continues to increase. Currently, plug-in electric vehicles require an onboard conductive charger to regulate the power delivered to the HV battery and isolate the HV bus from the AC grid. In some cases, electric vehicles may offer the option for supplying AC power to connected loads thus providing the flexibility of using the onboard HV battery as a mobile source. Moreover, with increased consumer demand for hands-free charging, wireless power transfer can potentially be considered as an addon option to serve as an HV battery charger. Unfortunately, due to the limited onboard space and the high cost of the power conversion system, adoption of the wireless power transfer technology has not gained traction. This dissertation provides a comprehensive study outlining the challenges with adding a wireless HV battery charger to battery-electric and plug-in hybrid vehicles. Through system architecture analysis, a case is made for why there is a need to consolidate the redundant onboard circuit blocks through system-level integration. Opportunities for reducing the onboard bill-of-material cost and reducing the size of the onboard electronics are provided. Moreover, the technological challenges with the overall power conversion efficiency as it pertains to a highly integrated system are discussed. Also, the challenge of realizing system interoperability with the public charging infrastructure for the wireless power transfer system is addressed. Battery electric and plug-in hybrid vehicles capable of wirelessly charging the HV battery have the advantage of charging while in motion, during frequent stops, and automatically in public designated parking areas. With such flexibility in receiving power, the battery size can be reduced, allowing for a reduction (open full item for complete abstract)

Committee: Jin Wang (Advisor); Lee Robert (Committee Member); Zhang Julia (Committee Member); Illindala Mahesh (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy (PhD), Wright State University, 2020, Electrical Engineering

In the future, renewable energy sources will be the primary energy sources due to non-renewable energy resources depletion. Having a sustainable energy source as an input voltage source for the electrical system is essential. Its applications can be widely used in hybrid solar-wind energy systems, electric vehicles, etc. This converter is invented and named after by Slobodan Cuk. An analysis describing a detailed steady-state operation of the non-isolated Cuk converter operating in continuous-conduction mode (CCM) is provided. The expected steady-state current and voltage waveforms across different components of the converter are analytically derived. Design equations for the converter are provided. The power loss of various converter components is predicted. The overall converter efficiency is derived. By using circuit averaging technique, the dc and the small-signal ac models of the non-isolated Cuk dc-dc converter operating in CCM are derived. The transfer functions of the non-isolated Cuk dc-dc converter power-stage are duty cycle-to-output voltage, input voltage-to-output voltage, output impedance, and input impedance. The component parasitics of the converter are included. Output voltage step responses to the duty cycle and input voltage step changes are provided. The time-domain and frequency-domain characteristics of the converter are analyzed by using a design example. Simulation and experimental results are provided, validating the theoretical results. This verified model responses from simulations are also validated through hardware implementation. A closed-loop voltage-mode controller for the non-isolated Cuk dc-dc converter is designed. Various frequency-domain parameters affecting the system responses are measured and compared to the open-loop system. All the theoretically obtained responses are implemented using MATLAB and experimentation.

Committee: Marian K. Kazimierczuk Ph.D. (Advisor); Yan Zhuang Ph.D. (Committee Member); Saiyu Ren Ph.D. (Committee Member); Henry Chen Ph.D. (Committee Member); Ray Siferd Ph.D. (Committee Member) Subjects: Electrical Engineering

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

DC distribution networks have found increased applications in electric automobiles, ships, aircrafts, server farms, and EV charging stations. These networks contain load regulating power electronic converters such as dc-dc and dc-ac converters that act as Constant Power Loads (CPLs). When these CPLs interact with the dc system, they can cause destabilizing effects on the grid due to their negative incremental impedance. Preliminary studies have performed stability analysis of dc distribution systems and proposed passive stabilization and source/load converter level controlstrategies to address the instability issue which does not address all the stability issues of multi-terminal dc distribution systems. In this research, a method to dynamically stabilize CPLs at the point of load by making them behave as adaptive Smart Resistors using high bandwidth power converters and energy storage units has been proposed. By utilizing high bandwidth power converters, these Smart Resistors can work with smart sources to realize ultimate intelligent power networks. This research aims to identify the realization of the smart Resistor concept and its utilization in the control of dc distribution systems. The effect of the Smart Resistor on the stability of various configurations of dc distribution networks are studied. The aims of this research study are as follows: The control strategies needed to achieve the Smart Resistor concept. The trajectory control of the system during voltage and current transients are studied. The energy management of energy storage is also proposed. The interaction of a constant power load powered by an ideal voltage source and a case study of a traction drive system is performed and the small and large-signal stability of the system is analyzed. The stability of a non-ideal source power converter feeding a constant power load. A case study of a section of a turbo-electric aircraft is used to showcase how the CPL (open full item for complete abstract)

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

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

With the increasing demand for lowering the power consumption, system cost and size of high-performance electronic devices, power supply designers are being challenged to develop unconventional design techniques so that the efficiency and power density of the power supplies used in these systems could be improved to help meet these demands. On the one hand, linear power supplies can be small and cost-effective as they require no inductors. However, their poor efficiency makes them unattractive in terms of lowering the system power consumption. Moreover, the bulky and expensive heat sinks desired to dissipate the heat resulting from their poor efficiency offset their small size and lower cost advantage. On the other hand, switching power supplies offer much higher efficiency, but require bulky and expensive inductors, unless new design techniques are developed to reduce their impact on the system size and cost. To address these challenges, the work presented in this thesis is focused and performed on the development of new design techniques for switching power supplies to target two distinct applications namely, a) CPUs used in high-performance computer servers, and b) battery-operated mobile devices. Designing switching power converters for CPU's in high-performance computer server applications is becoming increasingly difficult. This is because higher performance in a CPU necessitates for the following requirements from switching converter that powers it: (a) higher maximum load current rating, (b) high efficiency across a wider load range, and (c) fast Dynamic Voltage Scaling (DVS). Based on this context, the research work documented in this thesis includes two different high-frequency, high-current switching power converter techniques designed to incorporate the above key parameters. The first proposed technique for high performance CPU applications is a 4-phase buck converter design with maximum load of 8 A. The converter switches at 100 MHz to enable fast dy (open full item for complete abstract)

Committee: Ayman Fayed Dr. (Advisor); Anant Agarwal Dr. (Committee Member); Tawfiq Musah Dr. (Committee Member); Andrea Sims Dr. (Committee Member) Subjects: Electrical Engineering

Master of Science in Electrical Engineering (MSEE), Wright State University, 2020, Electrical Engineering

Military aircraft systems' power losses are occurring during the loading operations; loading and unloading causes the aircraft systems to lose power. The primary aircraft power source is provided by a 400Hz Ground Power Units (GPU). This GPU provides power to interior lighting, the aircraft cargo compartment, and other electrical systems (i.e. bus). The issues are during loading and unloading on the aircraft, which causes dropout of aircraft power supplied by the external 400Hz GPU. The majority of the military aircraft require a high voltage and a high current with a 270V power output. This thesis analyzes using Feed-Forward PWM Boost DC-DC Control Converter to help maintain 270V power output. The Feed-Forward PWM Boost DC-DC Control Converter design equations are operating in Continuous Conduction Mode (CCM) and all theoretical simulation responses were verified using Saber circuit simulator. The design and simulation results are documented in this thesis

Committee: Marian K. Kazimierczuk Ph.D. (Advisor); Saiyu Ren Ph.D. (Committee Member); Yan Zhuang Ph.D. (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy (PhD), Wright State University, 2020, Electrical Engineering

The pulse-width modulated (PWM) dc-dc converters play a vital role in several industrial applications that include motor drives, electric vehicles, dc distribution systems, and consumer electronics. The switched-mode power converters step the input voltage up or down based on their typology and provide a regulated output voltage. The stability and regulation performance of a power converter can tremendously be improved via a suitable control design. However, due to the nonlinearity of the power converters and the presence of the line and load disturbances, the design of a robust and low-cost control circuit becomes a challenging task. The sliding-mode control of the dc-dc converters has been studied for decades because of its robustness, design simplicity, and suitability for variable structure systems. Despite the merits of the sliding-mode control method, the linear controllers are still dominant and attractive to the commercial applications since they require less design efforts and can be implemented using simple analogue circuits. This research aims to develop simplified sliding-mode control circuits for the classical PWM dc-dc converters in continuous-conduction mode (CCM). The control objectives are to maintain a constant switching frequency, enhance the transient response, provide wide operating range, and track the desired reference voltage under large disturbances. In order to design and test the control circuit, an accurate power converter model should be derived. Hence, large-signal non-ideal averaged models of dc-dc buck and boost converters in CCM are developed. The models are simulated in MATLAB/SIMULINK and compared with the corresponding circuits in SaberRD simulator for validation purpose. Next, PWM-based simplified sliding-mode voltage and current control schemes are designed for the dc-dc buck and boost converters in CCM, respectively. The design procedure and the analogue realization of the control equations are presented, where the control c (open full item for complete abstract)

Committee: Marian K. Kazimierczuk Ph.D. (Advisor); Raúl Ordóñez Ph.D. (Committee Member); Saiyu Ren Ph.D. (Committee Member); Yan Zhuang Ph.D. (Committee Member); Xiaodong Zhang Ph.D. (Committee Member) Subjects: Electrical Engineering