+publisher:"Virginia Tech" +contributor:("Burgos, Rolando")

Virginia Tech

1. Rashidi Mehrabadi, Niloofar. On Methodology for Verification, Validation and Uncertainty Quantification in Power Electronic Converters Modeling.

Degree: MS, Electrical Engineering, 2014, Virginia Tech

URL: http://hdl.handle.net/10919/50524

► This thesis provides insight into quantitative accuracy assessment of the modeling and simulation of power electronic converters. Verification, Validation, and Uncertainty quantification (VVandUQ) provides a… (more)

Subjects/Keywords: power electronic converters; Uncertainty Quantification (UQ); modeling and simulation

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APA (6^th Edition):

Rashidi Mehrabadi, N. (2014). On Methodology for Verification, Validation and Uncertainty Quantification in Power Electronic Converters Modeling. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/50524

Chicago Manual of Style (16^th Edition):

Rashidi Mehrabadi, Niloofar. “On Methodology for Verification, Validation and Uncertainty Quantification in Power Electronic Converters Modeling.” 2014. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/50524.

MLA Handbook (7^th Edition):

Rashidi Mehrabadi, Niloofar. “On Methodology for Verification, Validation and Uncertainty Quantification in Power Electronic Converters Modeling.” 2014. Web. 28 Feb 2021.

Vancouver:

Rashidi Mehrabadi N. On Methodology for Verification, Validation and Uncertainty Quantification in Power Electronic Converters Modeling. [Internet] [Masters thesis]. Virginia Tech; 2014. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/50524.

Council of Science Editors:

Rashidi Mehrabadi N. On Methodology for Verification, Validation and Uncertainty Quantification in Power Electronic Converters Modeling. [Masters Thesis]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/50524

Virginia Tech

2. Rong, Yu. A Synchronous Distributed Control and Communication Network for High-Frequency SiC-Based Modular Power Converters.

Degree: MS, Electrical Engineering, 2019, Virginia Tech

URL: http://hdl.handle.net/10919/96395

► The power electronics building block (PEBB) concept is proposed for medium-voltage converter applications in order to realize the modular design of the power stage. Traditionally,… (more)

Subjects/Keywords: communication network; distributed control; synchronization; low latency; modular power converters; SiC MOSFET

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APA (6^th Edition):

Rong, Y. (2019). A Synchronous Distributed Control and Communication Network for High-Frequency SiC-Based Modular Power Converters. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/96395

Chicago Manual of Style (16^th Edition):

Rong, Yu. “A Synchronous Distributed Control and Communication Network for High-Frequency SiC-Based Modular Power Converters.” 2019. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/96395.

MLA Handbook (7^th Edition):

Rong, Yu. “A Synchronous Distributed Control and Communication Network for High-Frequency SiC-Based Modular Power Converters.” 2019. Web. 28 Feb 2021.

Vancouver:

Rong Y. A Synchronous Distributed Control and Communication Network for High-Frequency SiC-Based Modular Power Converters. [Internet] [Masters thesis]. Virginia Tech; 2019. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/96395.

Council of Science Editors:

Rong Y. A Synchronous Distributed Control and Communication Network for High-Frequency SiC-Based Modular Power Converters. [Masters Thesis]. Virginia Tech; 2019. Available from: http://hdl.handle.net/10919/96395

Virginia Tech

3. Raszmann, Emma Barbara. Series-Connection of Silicon Carbide MOSFET Modules using Active Gate-Drivers with dv/dt Control.

Degree: MS, Electrical Engineering, 2019, Virginia Tech

URL: http://hdl.handle.net/10919/95938

► According to ABB, 40% of the world's power demand is supplied by electrical energy. Specifically, in 2018, the world's electrical demand has grown by 4%… (more)

▼ According to ABB, 40% of the world's power demand is supplied by electrical energy. Specifically, in 2018, the world's electrical demand has grown by 4% since 2010. The growing need for electric energy makes it increasingly essential for systems that can efficiently and reliably convert and control energy levels for various end applications, such as electric motors, electric vehicles, data centers, and renewable energy systems. Power electronics are systems by which electrical energy is converted to different levels of power (voltage and current) depending on the end application. The use of power electronics systems is critical for controlling the flow of electrical energy in all applications of electric energy generation, transmission, and distribution. Advances in power electronics technologies, such as new control techniques and manufacturability of power semiconductor devices, are enabling improvements to the overall performance of electrical energy conversion systems. Power semiconductor devices, which are used as switches or rectifiers in various power electronic converters, are a critical building block of power electronic systems. In order to enable higher output power capability for converter systems, power semiconductor switches are required to sustain higher levels of voltage and current. Wide bandgap semiconductor devices are a particular new category of power semiconductors that have superior material properties compared to traditional devices such as Silicon (Si) Insulated-Gate Bipolar Junction Transistors (IGBTs). In particular, wide bandgap devices such as Silicon Carbide (SiC) Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) have better ruggedness and thermal capabilities. These properties provide wide bandgap semiconductor devices to operate at higher temperatures and switching frequencies, which is beneficial for maximizing the overall efficiency and volume of power electronic converters. This work investigates a method of scaling up voltage in particular for medium-voltage power conversion, which can be applied for a variety of application areas. SiC MOSFET devices are becoming more attractive for utilization in medium-voltage high-power converter systems due to the need to further improve the efficiency and density of these systems. Rather than using individual high voltage rated semiconductor devices, this thesis demonstrates the effectiveness of using several low voltage rated semiconductor devices connected in series in order to operate them as a single switch. Using low voltage devices as a single series-connected switch rather than a using single high voltage switch can lead to achieving a lower total on-state resistance, expectedly maximizing the overall efficiency of converter systems for which the series-connected semiconductor switches would be applied. In particular, this thesis focuses on the implementation of a newer approach of compensating for the natural unbalance in voltage between series-connected devices. An active gate control method is used for monitoring and… Advisors/Committee Members: Burgos, Rolando (committeechair), Dong, Dong (committee member), Boroyevich, Dushan (committee member).

Subjects/Keywords: series-connected devices; silicon carbide (SiC); metal-oxide-semiconductor field-effect transistor (MOSFET); gate-driver design; active gate control; active dv/dt control; medium-voltage; voltage balancing

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APA (6^th Edition):

Raszmann, E. B. (2019). Series-Connection of Silicon Carbide MOSFET Modules using Active Gate-Drivers with dv/dt Control. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/95938

Chicago Manual of Style (16^th Edition):

Raszmann, Emma Barbara. “Series-Connection of Silicon Carbide MOSFET Modules using Active Gate-Drivers with dv/dt Control.” 2019. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/95938.

MLA Handbook (7^th Edition):

Raszmann, Emma Barbara. “Series-Connection of Silicon Carbide MOSFET Modules using Active Gate-Drivers with dv/dt Control.” 2019. Web. 28 Feb 2021.

Vancouver:

Raszmann EB. Series-Connection of Silicon Carbide MOSFET Modules using Active Gate-Drivers with dv/dt Control. [Internet] [Masters thesis]. Virginia Tech; 2019. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/95938.

Council of Science Editors:

Raszmann EB. Series-Connection of Silicon Carbide MOSFET Modules using Active Gate-Drivers with dv/dt Control. [Masters Thesis]. Virginia Tech; 2019. Available from: http://hdl.handle.net/10919/95938

Virginia Tech

4. Wang, Qiong. Design of Extreme Efficiency Active Rectifier for More-electric Aircrafts.

Degree: MS, Electrical and Computer Engineering, 2015, Virginia Tech

URL: http://hdl.handle.net/10919/78147

► The More-electric aircraft (MEA) concept has been raised since 1990s in order to increase fuel economy and reduce environmental impact of aircrafts. The fundamental of… (more)

▼ The More-electric aircraft (MEA) concept has been raised since 1990s in order to increase fuel economy and reduce environmental impact of aircrafts. The fundamental of the concept is to replace pneumatic, hydraulic and mechanical systems in conventional aircrafts with its electrical equivalent that is lighter and more reliable. In this movement, power electronics technology plays a key role in interfacing the new types of electrical loads to the new aircraft electrical power system. One of the major tasks for power electronics circuits in MEA is to transfer aircraft variable frequency AC voltage into DC voltage, which could be conveniently utilized by different types of loads or power buses. The converters carrying out the task is commonly known as "rectifiers". This work aims at designing and constructing rectifiers that can work efficiently and reliably in more-electric aircrafts. One of the major challenge for these rectifiers comes from the complex aircraft environment. The ambient temperature could be as high as 70 ºC. Moreover, active cooling for converters may not be desirable. To deal with this, rectifiers should achieve extreme efficiency (especially at full load) so that all the components are not overheated without active cooling. This work aims at achieving extreme converter efficiency through advanced converter topologies and design. Both single-phase and three-phase rectifiers are discussed in this work. For single-phase rectifiers, this work focused on boost-type power factor correction (PFC) converters due to the promising efficiency and good PFC characteristics. The well-known two-level semi-bridgeless PFC boost rectifier, together with its interleaved and three-level counterparts, are studied and compared in this work. The operation principles of the converters are analyzed. Models and methods for converter efficiency evaluation are discussed. The efficiency evaluation of the topologies shows the advantage of three-level topologies and interleaved topologies in achieving higher efficiency and better thermal management. For three-phase rectifiers, two-level boost rectifier, three-level neutral point clamped (NPC) rectifier and Vienna rectifier are investigated. The evaluation shows the advantage of Vienna rectifier in achieving high efficiency due to reduced switching loss. Based on the evaluation of single-phase and three-phase active rectifiers, the author selected interleaved Vienna rectifier to achieve extreme efficiency and avoid overheating problem. The operation principle of the interleaved Vienna rectifier is introduced, with particular attention paid to the circulating current generated by interleaving operation. The design procedure for achieving maximum efficiency is described. Finally, a prototype of the proposed converter is constructed, which achieves 99.26% efficiency at nominal load. Advisors/Committee Members: Burgos, Rolando (committeechair), Boroyevich, Dushan (committee member), Li, Qiang (committee member).

Subjects/Keywords: High efficiency; more-electric aircrafts; PFC converter; interleaved converter; Vienna converter

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APA (6^th Edition):

Wang, Q. (2015). Design of Extreme Efficiency Active Rectifier for More-electric Aircrafts. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78147

Chicago Manual of Style (16^th Edition):

Wang, Qiong. “Design of Extreme Efficiency Active Rectifier for More-electric Aircrafts.” 2015. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/78147.

MLA Handbook (7^th Edition):

Wang, Qiong. “Design of Extreme Efficiency Active Rectifier for More-electric Aircrafts.” 2015. Web. 28 Feb 2021.

Vancouver:

Wang Q. Design of Extreme Efficiency Active Rectifier for More-electric Aircrafts. [Internet] [Masters thesis]. Virginia Tech; 2015. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/78147.

Council of Science Editors:

Wang Q. Design of Extreme Efficiency Active Rectifier for More-electric Aircrafts. [Masters Thesis]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/78147

Virginia Tech

5. Zhou, Bo. D-q impedance identification in three phase systems using multi-tone perturbation.

Degree: MS, Electrical Engineering, 2013, Virginia Tech

URL: http://hdl.handle.net/10919/50924

► In electric power systems, the existence of constant power loads such as output-regulated power converters may bring instability problem to AC or DC distributed systems.… (more)

Subjects/Keywords: d-q impedance; multi-tone; diode bridge rectifier

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APA (6^th Edition):

Zhou, B. (2013). D-q impedance identification in three phase systems using multi-tone perturbation. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/50924

Chicago Manual of Style (16^th Edition):

Zhou, Bo. “D-q impedance identification in three phase systems using multi-tone perturbation.” 2013. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/50924.

MLA Handbook (7^th Edition):

Zhou, Bo. “D-q impedance identification in three phase systems using multi-tone perturbation.” 2013. Web. 28 Feb 2021.

Vancouver:

Zhou B. D-q impedance identification in three phase systems using multi-tone perturbation. [Internet] [Masters thesis]. Virginia Tech; 2013. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/50924.

Council of Science Editors:

Zhou B. D-q impedance identification in three phase systems using multi-tone perturbation. [Masters Thesis]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/50924

Virginia Tech

6. DiMarino, Christina Marie. High Temperature Characterization and Analysis of Silicon Carbide (SiC) Power Semiconductor Transistors.

Degree: MS, Electrical and Computer Engineering, 2014, Virginia Tech

URL: http://hdl.handle.net/10919/78116

► This thesis provides insight into state-of-the-art 1.2 kV silicon carbide (SiC) power semiconductor transistors, including the MOSFET, BJT, SJT, and normally-on and normally-off JFETs. Both… (more)

Subjects/Keywords: power semiconductor devices; SiC MOSFET; SiC BJT; SiC JFET; high temperature; characterization; silicon carbide

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APA (6^th Edition):

DiMarino, C. M. (2014). High Temperature Characterization and Analysis of Silicon Carbide (SiC) Power Semiconductor Transistors. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78116

Chicago Manual of Style (16^th Edition):

DiMarino, Christina Marie. “High Temperature Characterization and Analysis of Silicon Carbide (SiC) Power Semiconductor Transistors.” 2014. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/78116.

MLA Handbook (7^th Edition):

DiMarino, Christina Marie. “High Temperature Characterization and Analysis of Silicon Carbide (SiC) Power Semiconductor Transistors.” 2014. Web. 28 Feb 2021.

Vancouver:

DiMarino CM. High Temperature Characterization and Analysis of Silicon Carbide (SiC) Power Semiconductor Transistors. [Internet] [Masters thesis]. Virginia Tech; 2014. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/78116.

Council of Science Editors:

DiMarino CM. High Temperature Characterization and Analysis of Silicon Carbide (SiC) Power Semiconductor Transistors. [Masters Thesis]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/78116

Virginia Tech

7. Rankin, Paul Edward. Modeling and Design of a SiC Zero Common-Mode Voltage Three-Level DC/DC Converter.

Degree: MS, Electrical Engineering, 2019, Virginia Tech

URL: http://hdl.handle.net/10919/93176

► As material advancements allow for the creation of devices with superior electrical characteristics compared to their predecessors, there are still a number of factors which… (more)

Subjects/Keywords: Silicon Carbide; Common-Mode Voltage; Neutral Point Clamped Converter; EMI; DC/DC

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APA (6^th Edition):

Rankin, P. E. (2019). Modeling and Design of a SiC Zero Common-Mode Voltage Three-Level DC/DC Converter. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/93176

Chicago Manual of Style (16^th Edition):

Rankin, Paul Edward. “Modeling and Design of a SiC Zero Common-Mode Voltage Three-Level DC/DC Converter.” 2019. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/93176.

MLA Handbook (7^th Edition):

Rankin, Paul Edward. “Modeling and Design of a SiC Zero Common-Mode Voltage Three-Level DC/DC Converter.” 2019. Web. 28 Feb 2021.

Vancouver:

Rankin PE. Modeling and Design of a SiC Zero Common-Mode Voltage Three-Level DC/DC Converter. [Internet] [Masters thesis]. Virginia Tech; 2019. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/93176.

Council of Science Editors:

Rankin PE. Modeling and Design of a SiC Zero Common-Mode Voltage Three-Level DC/DC Converter. [Masters Thesis]. Virginia Tech; 2019. Available from: http://hdl.handle.net/10919/93176

Virginia Tech

8. Mocevic, Slavko. PCB-Embedded Phase Current Sensor and Short-Circuit Detector for High Power SiC-Based Converters.

Degree: MS, Electrical Engineering, 2018, Virginia Tech

URL: http://hdl.handle.net/10919/84348

► Together with renewable sources, electric vehicle will play an important role as a part of sustainable and renewable energy future by significantly reducing emissions of… (more)

Subjects/Keywords: SiC MOSFET; Rogowski coil; switch current sensor; phase current sensor; short-circuit protection; desaturation

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APA (6^th Edition):

Mocevic, S. (2018). PCB-Embedded Phase Current Sensor and Short-Circuit Detector for High Power SiC-Based Converters. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/84348

Chicago Manual of Style (16^th Edition):

Mocevic, Slavko. “PCB-Embedded Phase Current Sensor and Short-Circuit Detector for High Power SiC-Based Converters.” 2018. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/84348.

MLA Handbook (7^th Edition):

Mocevic, Slavko. “PCB-Embedded Phase Current Sensor and Short-Circuit Detector for High Power SiC-Based Converters.” 2018. Web. 28 Feb 2021.

Vancouver:

Mocevic S. PCB-Embedded Phase Current Sensor and Short-Circuit Detector for High Power SiC-Based Converters. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/84348.

Council of Science Editors:

Mocevic S. PCB-Embedded Phase Current Sensor and Short-Circuit Detector for High Power SiC-Based Converters. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/84348

Virginia Tech

9. Noon, John Patrick. Development of a Power Hardware-in-the-Loop Test Bench for Electric Machine and Drive Emulation.

Degree: MS, Electrical Engineering, 2020, Virginia Tech

URL: http://hdl.handle.net/10919/101498

► According to the International Energy Agency (IEA), electric power usage is increasing across all sectors, and particularly in the transportation sector [1]. This increase is… (more)

▼ According to the International Energy Agency (IEA), electric power usage is increasing across all sectors, and particularly in the transportation sector [1]. This increase is apparent in one's daily life through the increase of electric vehicles on the road. Power electronics convert electricity in one form to electricity in another form. This conversion of power is playing an increasingly important role in society because examples of this conversion include converting the dc voltage of a battery to ac voltage in an electric car or the conversion of the ac power grid to dc to power a laptop. Additionally, even within an electric car, power converters transform the battery's electric power from a higher dc voltage into lower voltage dc power to supply the entertainment system and into ac power to drive the car's motor. The electrification of the transportation sector is leading to an increase in the amount of electric energy that is being consumed and processed through power electronics. As was illustrated in the previous examples of electric cars, the application of power electronics is very wide and thus requires different testbenches for the many different applications. While some industries are used to power electronics and testing converters, transportation electrification is increasing the number of companies and industries that are using power electronics and electric machines. As industry is shifting towards these new technologies, it is a prime opportunity to change the way that high power testing is done for electric machines and power converters. Traditional testing methods are potentially dangerous and lack the flexibility that is required to test a wide variety of machines and drives. Power hardware-in-the-loop (PHIL) testing presents a safe and adaptable solution to high power testing of electric machines. Traditionally, electric machines were primarily used in heavy industry such as milling, processing, and pumping applications. These applications, and other applications such as an electric motor in a car or plane are called motor drive systems. Regardless of the particular application of the motor drive system, there are generally three parts: a dc source, an inverter, and the electric machine. In most applications, other than cars which have a dc battery, the dc source is a power electronic converter called a rectifier which converts ac electricity from the grid to dc for the motor drive. Next, the motor drive converts the dc electricity from the first stage to a controlled ac output to drive the electric machine. Finally, the electric machine itself is the final piece of the electrical system and converts the electrical energy to mechanical energy which can drive a fan, belt, or axle. The fact that this motor drive system can be generalized and applied to a wide range of applications makes its study particularly interesting. PHIL simplifies testing of these motor drive systems by allowing the inverter to connect directly to a machine emulator which is able to replicate a variety of loads.… Advisors/Committee Members: Burgos, Rolando (committeechair), Boroyevich, Dushan (committee member), Wen, Bo (committee member).

Subjects/Keywords: Power Hardware-in-the-Loop (PHIL); real-time simulation; induction machine emulation; motor drive systems; AC/DC conversion; DC/AC conversion

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APA (6^th Edition):

Noon, J. P. (2020). Development of a Power Hardware-in-the-Loop Test Bench for Electric Machine and Drive Emulation. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/101498

Chicago Manual of Style (16^th Edition):

Noon, John Patrick. “Development of a Power Hardware-in-the-Loop Test Bench for Electric Machine and Drive Emulation.” 2020. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/101498.

MLA Handbook (7^th Edition):

Noon, John Patrick. “Development of a Power Hardware-in-the-Loop Test Bench for Electric Machine and Drive Emulation.” 2020. Web. 28 Feb 2021.

Vancouver:

Noon JP. Development of a Power Hardware-in-the-Loop Test Bench for Electric Machine and Drive Emulation. [Internet] [Masters thesis]. Virginia Tech; 2020. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/101498.

Council of Science Editors:

Noon JP. Development of a Power Hardware-in-the-Loop Test Bench for Electric Machine and Drive Emulation. [Masters Thesis]. Virginia Tech; 2020. Available from: http://hdl.handle.net/10919/101498

Virginia Tech

10. Salvo, Christopher. Design and Implementation of a Multiphase Buck Converter for Front End 48V-12V Intermediate Bus Converters.

Degree: MS, Electrical Engineering, 2019, Virginia Tech

URL: http://hdl.handle.net/10919/101938

► The trend in isolated DC/DC bus converters is to increase the output power in the same brick form factors that have been used in the… (more)

▼ The trend in isolated DC/DC bus converters is to increase the output power in the same brick form factors that have been used in the past. Traditional intermediate bus converters (IBCs) use silicon power metal oxide semiconductor field effect transistors (MOSFETs), which recently have reached the limit in terms of turn on resistance (RDSON) and switching frequency. In order to make the IBCs smaller, the switching frequency needs to be pushed higher, which will in turn shrink the magnetics, lowering the converter size, but increase the switching related losses, lowering the overall efficiency of the converter. Wide-bandgap semiconductor devices are becoming more popular in commercial products and gallium nitride (GaN) devices are able to push the switching frequency higher without sacrificing efficiency. GaN devices can shrink the size of the converter and provide better efficiency than its silicon counterpart provides. A survey of current IBCs was conducted in order to find a design point for efficiency and power density. A two-stage converter topology was explored, with a multiphase buck converter as the front end, followed by an LLC resonant converter. The multiphase buck converter provides regulation, while the LLC provides isolation. With the buck converter providing regulation, the switching frequency of the entire converter will be constant. A constant switching frequency allows for better electromagnetic interference (EMI) mitigation. This work includes the details to design and implement a hard-switched multiphase buck converter with planar magnetics using GaN devices. The efficiency includes both the buck efficiency and the overall efficiency of the two-stage converter including the LLC. The buck converter operates with 40V - 60V input, nominally 48V, and outputs 36V at 1 kW, which is the input to the LLC regulating 36V – 12V. Both open and closed loop was measured for the buck and the full converter. EMI performance was not measured or addressed in this work. Advisors/Committee Members: Burgos, Rolando (committeechair), Li, Qiang (committee member), Boroyevich, Dushan (committee member).

Subjects/Keywords: Multiphase Buck; Planar Magnetics; Average Current Mode Control; Intermediate Bus Converter; Gallium Nitride; Two-Stage Converter

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APA (6^th Edition):

Salvo, C. (2019). Design and Implementation of a Multiphase Buck Converter for Front End 48V-12V Intermediate Bus Converters. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/101938

Chicago Manual of Style (16^th Edition):

Salvo, Christopher. “Design and Implementation of a Multiphase Buck Converter for Front End 48V-12V Intermediate Bus Converters.” 2019. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/101938.

MLA Handbook (7^th Edition):

Salvo, Christopher. “Design and Implementation of a Multiphase Buck Converter for Front End 48V-12V Intermediate Bus Converters.” 2019. Web. 28 Feb 2021.

Vancouver:

Salvo C. Design and Implementation of a Multiphase Buck Converter for Front End 48V-12V Intermediate Bus Converters. [Internet] [Masters thesis]. Virginia Tech; 2019. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/101938.

Council of Science Editors:

Salvo C. Design and Implementation of a Multiphase Buck Converter for Front End 48V-12V Intermediate Bus Converters. [Masters Thesis]. Virginia Tech; 2019. Available from: http://hdl.handle.net/10919/101938

11. Li, Chi. Design, Analysis and Experimental Evaluation of a Virtual Synchronous Machine Based Control Scheme for STATCOM Applications.

Degree: MS, Electrical and Computer Engineering, 2015, Virginia Tech

URL: http://hdl.handle.net/10919/78158

► Because renewable energy sources are environment-friendly and inexhaustible, more and more renewable energy power plants have been integrated into power grids worldwide. To compensate for… (more)

▼ Because renewable energy sources are environment-friendly and inexhaustible, more and more renewable energy power plants have been integrated into power grids worldwide. To compensate for their inherent variability, STATCOMs are typically installed at the point of common coupling (PCC) to help their operation by regulating the PCC voltage. However under different contingencies, PCC voltage fluctuations in magnitude and frequency may impede the STATCOM from tracking the grid frequency correctly, hence worsening its overall compensation performance, and putting at risk the operation of the power plant. Further, the virtual synchronous machine (VSM) concept has recently been introduced to control grid-connected inverters emulating the behavior of rotating synchronous machines, in an effort to eliminate the shortcomings of conventional d-q frame phase-locked loops (PLL). In this dissertation, the VSM concept is extended by developing a STATCOM controller with it, which then behaves like a fully-adjustable synchronous condenser, including the adjustment of its "virtual" inertia and impedance. An average model in two D-Q frames is proposed to analyze the inherent dynamics of the VSM-based STATCOM controller with insight into impacts from the virtual parameters and a design guideline is then formulated. The proposed controller is compared against existent d-q frame STATCOM control strategies, evincing how the VSM-based approach guarantees an improved voltage regulation performance at the PCC by adjusting the phase of its compensating current during frequency fluctuations, in both simulation and experiment. Secondly, the dynamics of the VSM-based STATCOM controller in large signal sense is studied, especially its capability to ride through faults. Analysis is carried out with phasors to obtain a fundamental understanding at first and followed by state space equations to predict the transients analytically, which is validated by matching both simulation and experiment. The effects of two outer loops are also reviewed and some possible solutions are suggested and evaluated. Moreover, the relationship between the virtual inertia and the actual inertia is established and the dc capacitor sizing is discussed in a possibly more economical way. The start-up process of a VSM-based STATCOM is presented to implement a practical prototype as well. Advisors/Committee Members: Burgos, Rolando (committeechair), Boroyevich, Dushan (committee member), Mili, Lamine (committeecochair).

Subjects/Keywords: STATCOM; virtual synchronous machine; control

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APA (6^th Edition):

Li, C. (2015). Design, Analysis and Experimental Evaluation of a Virtual Synchronous Machine Based Control Scheme for STATCOM Applications. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78158

Chicago Manual of Style (16^th Edition):

Li, Chi. “Design, Analysis and Experimental Evaluation of a Virtual Synchronous Machine Based Control Scheme for STATCOM Applications.” 2015. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/78158.

MLA Handbook (7^th Edition):

Li, Chi. “Design, Analysis and Experimental Evaluation of a Virtual Synchronous Machine Based Control Scheme for STATCOM Applications.” 2015. Web. 28 Feb 2021.

Vancouver:

Li C. Design, Analysis and Experimental Evaluation of a Virtual Synchronous Machine Based Control Scheme for STATCOM Applications. [Internet] [Masters thesis]. Virginia Tech; 2015. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/78158.

Council of Science Editors:

Li C. Design, Analysis and Experimental Evaluation of a Virtual Synchronous Machine Based Control Scheme for STATCOM Applications. [Masters Thesis]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/78158

Virginia Tech

12. Hu, Jiewen. Current-Transformer Based Gate-Drive Power Supply With Reinforced Isolation.

Degree: MS, Electrical Engineering, 2018, Virginia Tech

URL: http://hdl.handle.net/10919/85050

► Wide-bandgap semiconductor devices have attracted widespread attention due to their superior performance compared to their silicon devices counterpart. To utilize its full benefits, this thesis… (more)

Subjects/Keywords: GaN; Gate-Drive Power Supply; Inter-winding capacitance; 20 kV insulation; Current Transformer

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APA (6^th Edition):

Hu, J. (2018). Current-Transformer Based Gate-Drive Power Supply With Reinforced Isolation. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/85050

Chicago Manual of Style (16^th Edition):

Hu, Jiewen. “Current-Transformer Based Gate-Drive Power Supply With Reinforced Isolation.” 2018. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/85050.

MLA Handbook (7^th Edition):

Hu, Jiewen. “Current-Transformer Based Gate-Drive Power Supply With Reinforced Isolation.” 2018. Web. 28 Feb 2021.

Vancouver:

Hu J. Current-Transformer Based Gate-Drive Power Supply With Reinforced Isolation. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/85050.

Council of Science Editors:

Hu J. Current-Transformer Based Gate-Drive Power Supply With Reinforced Isolation. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/85050

Virginia Tech

13. Gui, Yingying. Gate Driver for Phase Leg of Parallel Enhancement-Mode Gallium-Nitride (GaN) Transistors.

Degree: MS, Electrical Engineering, 2018, Virginia Tech

URL: http://hdl.handle.net/10919/83516

► With a higher power rating and broader application, Gallium nitride (GaN) is a promising next-generation power switch. The current four GaN HEMTs in paralleled phase… (more)

▼ With a higher power rating and broader application, Gallium nitride (GaN) is a promising next-generation power switch. The current four GaN HEMTs in paralleled phase leg that can block 400 V and conduct 200 A current is very beneficial, thus making the protection method on a GaN phase leg an urgent topic. This thesis starts with an overview of shortcircuit robustness among silicon (Si), silicon carbide (SiC) and GaN devices. An approximately safe operation area (SOA) for a GaN power switch will also be determined. The various common shortcircuit protection methods are mentioned. Additionally, current research on a GaN semiconductor is summarized. Among all of the protection methods, desaturation detection is selected and analyzed through simulation and then implemented in a parallel enhancement-mode high-electron-mobility transistor (E-HEMT) GaN phase leg. With this desaturation detection feature, the GaN E-HEMT can be turned off as quickly as 200 ns, and in the worst case, 500 ns, during a shortcircuit test. The phase leg survived a series of shortcircuit tests with shortcircuit protection. For the proposed protection scheme, the best-case reaction time (200 ns) is similar to others in the literature, while the shortcircuit peak current and peak energy are higher. The worst-case performance of this design is limited by both the gate driver and the device shortcircuit robustness. Due to the fast switching speed of the GaN HEMT, the false turn-on phenomenon caused by the Miller effect can be a problem. A shoot through may occur with one switch false turn on. The Miller clamp is added to the phase leg to improve its reliability. After the hardware was implemented, the Miller clamp was tested and verified through a double pulse test (DPT). Compared to the phase leg without the Miller clamp, the gate is better protected from gate voltage overshoot and undershoot. The switching loss is reduced by 20 percent by using a new gate driver IC with higher current driving capability. The degradation effect of GaN power switches in different shortcircuit pulses was also studied. The device passes through the shortcircuit tests, but any degradation effect that may change its parameters and influence its normal operation characteristic need to be addressed. Several GaN devices were selected and characterized after several shortcircuit tests to observe any degradation effect caused by the shortcircuit. The degradation test results reveal a "recovery effect" of the GaN HEMT used in this project. The parameter variations on threshold voltage and on-resistance recover to the original state, several hours after the shortcircuit test. The test results match with the conclusion drawn in degradation test conducts by other research groups that the parameter variation during shortcircuit test is negligible. Also, repetitively fast shortcircuit tests on the GaN HEMT show that the shortcircuit protection limit for this device under 400 V bus should be limited to 300 ns. Advisors/Committee Members: Burgos, Rolando (committeechair), Boroyevich, Dushan (committee member), Ngo, Khai D. (committee member).

Subjects/Keywords: Gate driver design; Gallium nitride; Desaturation detection; Miller clamp; Shortcircuit robustness

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APA (6^th Edition):

Gui, Y. (2018). Gate Driver for Phase Leg of Parallel Enhancement-Mode Gallium-Nitride (GaN) Transistors. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/83516

Chicago Manual of Style (16^th Edition):

Gui, Yingying. “Gate Driver for Phase Leg of Parallel Enhancement-Mode Gallium-Nitride (GaN) Transistors.” 2018. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/83516.

MLA Handbook (7^th Edition):

Gui, Yingying. “Gate Driver for Phase Leg of Parallel Enhancement-Mode Gallium-Nitride (GaN) Transistors.” 2018. Web. 28 Feb 2021.

Vancouver:

Gui Y. Gate Driver for Phase Leg of Parallel Enhancement-Mode Gallium-Nitride (GaN) Transistors. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/83516.

Council of Science Editors:

Gui Y. Gate Driver for Phase Leg of Parallel Enhancement-Mode Gallium-Nitride (GaN) Transistors. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/83516

Virginia Tech

14. Najmi, Vahid. Modeling, Control and Design Considerations for Modular Multilevel Converters.

Degree: MS, Electrical Engineering, 2015, Virginia Tech

URL: http://hdl.handle.net/10919/53703

► This thesis provides insight into state-of-the-art Modular Multilevel Converters (MMC) for medium and high voltage applications. Modular Multilevel Converters have increased in interest in many… (more)

▼ This thesis provides insight into state-of-the-art Modular Multilevel Converters (MMC) for medium and high voltage applications. Modular Multilevel Converters have increased in interest in many industrial applications, as they offer the following advantages: modularity, scalability, reliability, distributed location of capacitors, etc. In this study, the modeling, control and design considerations of modular based multilevel converters, with an emphasis on the reliability of the converter, is carried out. Both modular multilevel converters with half-bridge and full-bridge sub-modules are evaluated in order to provide a complete analysis of the converter. From among the family of modular based hybrid multilevel converters, the newly released Alternate Arm Converter (AAC) is considered for further assessment in this study. Thus, the modular multilevel converter with half-bridge and full-bridge power cells and the Alternate Arm Converter as a commercialized hybrid structure of this family are the main areas of study in this thesis. Finally, the DC fault analysis as one of the main issues related to conventional VSC converters is assessed for Modular Multilevel Converters (MMC) and the DC fault ride-through capability and DC fault current blocking ability is illustrated in both the Modular Multilevel Converter with Full-Bridge (FB) power cells and in the Alternate iii Arm Converter (AAC). Accordingly, the DC fault control scheme employed in the converter and the operation of the converter under the fault control scheme are explained. The main contributions of this study are as follows: The new D-Q model for the MMC is proposed for use in the design of the inner and outer loop control. The extended control scheme from the modular multilevel converter is employed to control the Alternate Arm Converters. A practical reliability-oriented sub-module capacitor bank design is described based on different reliability modeling tools. A Zero Current Switching (ZCS) scheme of the Alternate Arm Converter is presented in order to reduce the switching losses of the Director Switches (DS) and, accordingly, to implement the ZCS, a design procedure for the Arm inductor in the AAC is proposed. The capacitor voltage waveform is extracted analytically in different load power factors and the waveforms are verified by simulation results. A reliability-oriented switching frequency analysis for the modular multilevel converters is carried out to evaluate the effect of the switching frequency on the MMC's operation. For the latter, a DC fault analysis for the MMC with Full-Bridge (FB) power cells and the AAC is performed and a DC fault control scheme is employed to provide the capacitor voltage control and DC fault current limit, and is illustrated herein. Advisors/Committee Members: Burgos, Rolando (committeechair), Boroyevich, Dushan (committee member), Lai, Jih S. (committee member).

Subjects/Keywords: Modular Multilevel Converter (MMC); Alternate Arm Converter (AAC); DC Fault ride-through; Reliability-Oriented Design; Circulating Current Suppressing Control (CCSC); Capacitor Voltage Balance; Three- Phase Average Modeling; DQ axis Modeling

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APA (6^th Edition):

Najmi, V. (2015). Modeling, Control and Design Considerations for Modular Multilevel Converters. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/53703

Chicago Manual of Style (16^th Edition):

Najmi, Vahid. “Modeling, Control and Design Considerations for Modular Multilevel Converters.” 2015. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/53703.

MLA Handbook (7^th Edition):

Najmi, Vahid. “Modeling, Control and Design Considerations for Modular Multilevel Converters.” 2015. Web. 28 Feb 2021.

Vancouver:

Najmi V. Modeling, Control and Design Considerations for Modular Multilevel Converters. [Internet] [Masters thesis]. Virginia Tech; 2015. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/53703.

Council of Science Editors:

Najmi V. Modeling, Control and Design Considerations for Modular Multilevel Converters. [Masters Thesis]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/53703

Virginia Tech

15. Rye, Rebecca Pilar. Design and Evaluation of a Photovoltaic Inverter with Grid-Tracking and Grid-Forming Controls.

Degree: MS, Electrical Engineering, 2020, Virginia Tech

URL: http://hdl.handle.net/10919/97398

► Concerns about the current and future state of the environment has prompted government and non-profit agencies to enact regulatory legislation on fossil fuel emissions. In… (more)

▼ Concerns about the current and future state of the environment has prompted government and non-profit agencies to enact regulatory legislation on fossil fuel emissions. In 2017, electricity generation comprised 28% of total U.S. greenhouse gas emissions with 68% of this generation being due to coal combustion sources. As a result, utilities have retired a number of coal power plants and have employed alternative means of power generation, specifically renewable energy sources (RES). Most RES operate as variable-frequency ac sources (wind) or dc sources (solar) and are interfaced with the power grid through ac-dc-ac or dc-ac converters, respectively, which are power-electronic devices used to control the injection of power to the grid. Conventional converters synchronize with the grid by tracking the phase of the voltage at the point of common coupling (PCC) through a phase-locked loop (PLL). While power system dynamics significantly affect the performance of a PLL, and, subsequently, inverters' operation, the initial frequency regulation during grid events is attributed to the system's inherent inertia due to the multitude of synchronous machines (SM). However, with the steady increase of RES penetration, even while retaining the number of SM units, the net inertia in the system will decrease, thus resulting in prolonged responses in frequency regulation to the aforementioned dynamics. This thesis investigates the control of variable-frequency sources as conventional synchronous machines and provides a detailed design procedure of this control structure for photovoltaic (PV) inverter applications. Additionally, the stability of the connection of the inverter to the grid is analyzed using innovative stability analysis techniques which treat the inverter and control as a black box. In this manner, the inner-workings of the inverter need not be known, especially since it is proprietary information of the manufacturer, and the operator can measure the output response of the device to some input signal. In this work, it is found that the connection between the inverter and grid is stable with this new control scheme and comparable to conventional control structures. Additionally, the control based on synchronous machine characteristics shows improved stability for voltage and frequency regulation, which is key to maintaining a stable grid. Advisors/Committee Members: Burgos, Rolando (committeechair), Southward, Steve C. (committee member), Kekatos, Vasileios (committee member).

Subjects/Keywords: control; three-phase; high-power; PLL; virtual synchronous machine; renewable energy; dq ac impedance; GNC; stability

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APA (6^th Edition):

Rye, R. P. (2020). Design and Evaluation of a Photovoltaic Inverter with Grid-Tracking and Grid-Forming Controls. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/97398

Chicago Manual of Style (16^th Edition):

Rye, Rebecca Pilar. “Design and Evaluation of a Photovoltaic Inverter with Grid-Tracking and Grid-Forming Controls.” 2020. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/97398.

MLA Handbook (7^th Edition):

Rye, Rebecca Pilar. “Design and Evaluation of a Photovoltaic Inverter with Grid-Tracking and Grid-Forming Controls.” 2020. Web. 28 Feb 2021.

Vancouver:

Rye RP. Design and Evaluation of a Photovoltaic Inverter with Grid-Tracking and Grid-Forming Controls. [Internet] [Masters thesis]. Virginia Tech; 2020. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/97398.

Council of Science Editors:

Rye RP. Design and Evaluation of a Photovoltaic Inverter with Grid-Tracking and Grid-Forming Controls. [Masters Thesis]. Virginia Tech; 2020. Available from: http://hdl.handle.net/10919/97398

Virginia Tech

16. Yu, Jianghui. DC Fault Current Analysis and Control for Modular Multilevel Converters.

Degree: MS, Electrical and Computer Engineering, 2016, Virginia Tech

URL: http://hdl.handle.net/10919/78054

► Recent research into industrial applications of electric power conversion shows an increase in the use of renewable energy sources and an increase in the need… (more)

Subjects/Keywords: Medium-Voltage DC Distribution Systems; Fault Operation Control; Modular Multilevel Converters; Converter Design

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Yu, J. (2016). DC Fault Current Analysis and Control for Modular Multilevel Converters. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78054

Chicago Manual of Style (16^th Edition):

Yu, Jianghui. “DC Fault Current Analysis and Control for Modular Multilevel Converters.” 2016. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/78054.

MLA Handbook (7^th Edition):

Yu, Jianghui. “DC Fault Current Analysis and Control for Modular Multilevel Converters.” 2016. Web. 28 Feb 2021.

Vancouver:

Yu J. DC Fault Current Analysis and Control for Modular Multilevel Converters. [Internet] [Masters thesis]. Virginia Tech; 2016. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/78054.

Council of Science Editors:

Yu J. DC Fault Current Analysis and Control for Modular Multilevel Converters. [Masters Thesis]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/78054

Virginia Tech

17. Ayyagari, Sai Rama Usha. Modeling and Electrical Characterization of Ohmic Contacts on n-type GaN.

Degree: MS, Electrical Engineering, 2018, Virginia Tech

URL: http://hdl.handle.net/10919/82483

► As the current requirements of power devices are moving towards high frequency, high efficiency and high-power density, Silicon-based devices are reaching its limits which are… (more)

Subjects/Keywords: GaN; TLM; Sentaurus Modeling; Ohmic Contacts; Electrical Characterization

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APA (6^th Edition):

Ayyagari, S. R. U. (2018). Modeling and Electrical Characterization of Ohmic Contacts on n-type GaN. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/82483

Chicago Manual of Style (16^th Edition):

Ayyagari, Sai Rama Usha. “Modeling and Electrical Characterization of Ohmic Contacts on n-type GaN.” 2018. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/82483.

MLA Handbook (7^th Edition):

Ayyagari, Sai Rama Usha. “Modeling and Electrical Characterization of Ohmic Contacts on n-type GaN.” 2018. Web. 28 Feb 2021.

Vancouver:

Ayyagari SRU. Modeling and Electrical Characterization of Ohmic Contacts on n-type GaN. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/82483.

Council of Science Editors:

Ayyagari SRU. Modeling and Electrical Characterization of Ohmic Contacts on n-type GaN. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/82483

Virginia Tech

18. Liu, Zhengyang. Characterization and Failure Mode Analysis of Cascode GaN HEMT.

Degree: MS, Electrical Engineering, 2014, Virginia Tech

URL: http://hdl.handle.net/10919/49580

► Recent emerging gallium nitride (GaN) high electron mobility transistor (HEMT) is expected to be a promising candidate for high frequency power conversion techniques. Due to… (more)

▼ Recent emerging gallium nitride (GaN) high electron mobility transistor (HEMT) is expected to be a promising candidate for high frequency power conversion techniques. Due to the advantages of the material, the GaN HEMT has a better figure of merit (FOM) compared to the state-of-the-art silicon (Si) power metal oxide silicon field effect transistor (MOSFET), which allows the GaN HEMT to switch with faster transition and lower switching loss. By applying the GaN HEMT in a circuit design, it is possible to achieve high frequency, high efficiency, and high density power conversion at the same time. To characterize the switching performance of the GaN HEMT, an accurate behavior-level simulation model is developed in this thesis. The packaging related parasitic inductance, including both self-inductance and mutual-inductance, are extracted based on finite element analysis (FEA) methods. Then the accuracy of the simulation model is verified by a double-pulse tester, and the simulation results match well with experiment in terms of both device switching waveform and switching energy. Based on the simulation model, detailed loss breakdown and loss mechanism analysis are made. The cascode GaN HEMT has high turn-on loss due to the body diode reverse recovery of the low voltage Si MOSFET and the common source inductance (CSI) of the package; while the turn-off loss is extremely small attributing to the cascode structure. With this unique feature, the critical conduction mode (CRM) soft switching technique are applied to reduce the dominant turn on loss and increase converter efficiency significantly. The switching frequency is successfully pushed to 5MHz while maintaining high efficiency and good thermal performance. Traditional packaging method is becoming a bottle neck to fully utilize the advantages of GaN HEMT. So an investigation of the package influence on the cascode GaN HEMT is also conducted. Several critical parasitic inductors are identified, which cause high turn on loss and high parasitic ringing which may lead to device failure. To solve the issue, the stack-die package is proposed to eliminate all critical parasitic inductors, and as a result, reducing turn on loss by half and avoiding potential failure mode of the cascode GaN device effectively. Utilizing the proposed stack-die package and ZVS soft switching, the GaN HEMT high frequency, high efficiency, and high density power conversion capability can be further extended to a higher level. Advisors/Committee Members: Lee, Fred C. (committeechair), Burgos, Rolando (committee member), Li, Qiang (committee member).

Subjects/Keywords: cascode GaN; simulation model; loss analysis; soft switching; stack-die package

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APA (6^th Edition):

Liu, Z. (2014). Characterization and Failure Mode Analysis of Cascode GaN HEMT. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/49580

Chicago Manual of Style (16^th Edition):

Liu, Zhengyang. “Characterization and Failure Mode Analysis of Cascode GaN HEMT.” 2014. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/49580.

MLA Handbook (7^th Edition):

Liu, Zhengyang. “Characterization and Failure Mode Analysis of Cascode GaN HEMT.” 2014. Web. 28 Feb 2021.

Vancouver:

Liu Z. Characterization and Failure Mode Analysis of Cascode GaN HEMT. [Internet] [Masters thesis]. Virginia Tech; 2014. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/49580.

Council of Science Editors:

Liu Z. Characterization and Failure Mode Analysis of Cascode GaN HEMT. [Masters Thesis]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/49580

Virginia Tech

19. Turriate, Victor Omar. Design and Implementation of a Radiation Hardened GaN Based Isolated DC-DC Converter for Space Applications.

Degree: MS, Electrical Engineering, 2018, Virginia Tech

URL: http://hdl.handle.net/10919/98232

► Power converters used in high reliability radiation hardened space applications trail their commercial counterparts in terms of power density and efficiency. This is due to… (more)

▼ Power converters used in high reliability radiation hardened space applications trail their commercial counterparts in terms of power density and efficiency. This is due to the additional challenges that arise in the design of space rated power converters from the harsh environment they need to operate in, to the limited availability of space qualified components and field demonstrated power converter topologies. New radiation hardened Gallium Nitride (GaN) Field Effect Transistors (FETs) with their inherent radiation tolerance and superior performance over Silicon Power Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) are a promising alternative to improve power density and performance in space power converters. This thesis presents the considerations and design of a practical implementation of the Phase Shifted Full Bridge DC-DC Isolated converter with synchronous rectification for space applications. Recently released radiation hardened GaN FETs were used in the Full Bridge and synchronous rectifier power stages. A survey outlining the benefits of new radiation hardened GaN FETs for space power applications compared to current radiation hardened power MOSFETs is included. In addition, this work presents the overall design process followed to design the DC-DC converter power stage, as well as a comprehensive power loss analysis. Furthermore, this work includes details to implement a conventional hard-switched Full Bridge DC-DC converter for this application. An efficiency and component stress comparison was performed between the hard-switched Full Bridge design and the Phase Shifted Full Bridge DC-DC converter design. This comparison highlights the benefits of phase shift modulation (PSM) and zero voltage switching (ZVS) for GaN FET applications. Furthermore, different magnetic designs were characterized and compared for efficiency in both converters. The DC-DC converters implemented in this work regulate the output to a nominal 20 V, delivering 500 W from a nominal 100 V DC Bus input. Complete fault analysis and protection circuitry required for a space-qualified implementation is not addressed by this work. Advisors/Committee Members: Boroyevich, Dushan (committeechair), Burgos, Rolando (committeechair), Southward, Steve C. (committee member), Sable, Daniel M. (committee member).

Subjects/Keywords: Gallium Nitride; Phase Shifted Full Bridge; Current Doubler Rectifier; space; radiation hardened; rad-hard; DC-DC converter

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APA (6^th Edition):

Turriate, V. O. (2018). Design and Implementation of a Radiation Hardened GaN Based Isolated DC-DC Converter for Space Applications. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/98232

Chicago Manual of Style (16^th Edition):

Turriate, Victor Omar. “Design and Implementation of a Radiation Hardened GaN Based Isolated DC-DC Converter for Space Applications.” 2018. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/98232.

MLA Handbook (7^th Edition):

Turriate, Victor Omar. “Design and Implementation of a Radiation Hardened GaN Based Isolated DC-DC Converter for Space Applications.” 2018. Web. 28 Feb 2021.

Vancouver:

Turriate VO. Design and Implementation of a Radiation Hardened GaN Based Isolated DC-DC Converter for Space Applications. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/98232.

Council of Science Editors:

Turriate VO. Design and Implementation of a Radiation Hardened GaN Based Isolated DC-DC Converter for Space Applications. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/98232

Virginia Tech

20. Khanna, Mudit. Design of DC-DC converters using Tunable Piezoelectric Transformers.

Degree: MS, Electrical Engineering, 2017, Virginia Tech

URL: http://hdl.handle.net/10919/86442

► This thesis introduces the ‘tunable’ piezoelectric transformers (TPT) which provide an extra control terminal, used in this case, to regulate the output voltage. A detailed… (more)

Subjects/Keywords: Piezoelectric Transformers; DC-DC converters

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APA (6^th Edition):

Khanna, M. (2017). Design of DC-DC converters using Tunable Piezoelectric Transformers. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/86442

Chicago Manual of Style (16^th Edition):

Khanna, Mudit. “Design of DC-DC converters using Tunable Piezoelectric Transformers.” 2017. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/86442.

MLA Handbook (7^th Edition):

Khanna, Mudit. “Design of DC-DC converters using Tunable Piezoelectric Transformers.” 2017. Web. 28 Feb 2021.

Vancouver:

Khanna M. Design of DC-DC converters using Tunable Piezoelectric Transformers. [Internet] [Masters thesis]. Virginia Tech; 2017. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/86442.

Council of Science Editors:

Khanna M. Design of DC-DC converters using Tunable Piezoelectric Transformers. [Masters Thesis]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/86442

Virginia Tech

21. Pierce, Timothy M. Jr. Mobile Hybrid Power System Theory of Operation.

Degree: MS, Electrical and Computer Engineering, 2016, Virginia Tech

URL: http://hdl.handle.net/10919/78148

► Efficiency is a driving constraint for electrical power systems as global energy demands are ever increasing. Followed by the introduction of diesel generators, electricity has… (more)

Subjects/Keywords: power factor correction; load profile; energy storage; mobile hybrid power system; fuel consumption

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APA (6^th Edition):

Pierce, T. M. J. (2016). Mobile Hybrid Power System Theory of Operation. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78148

Chicago Manual of Style (16^th Edition):

Pierce, Timothy M Jr. “Mobile Hybrid Power System Theory of Operation.” 2016. Masters Thesis, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/78148.

MLA Handbook (7^th Edition):

Pierce, Timothy M Jr. “Mobile Hybrid Power System Theory of Operation.” 2016. Web. 28 Feb 2021.

Vancouver:

Pierce TMJ. Mobile Hybrid Power System Theory of Operation. [Internet] [Masters thesis]. Virginia Tech; 2016. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/78148.

Council of Science Editors:

Pierce TMJ. Mobile Hybrid Power System Theory of Operation. [Masters Thesis]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/78148

22. Dimarino, Christina Marie. Design and Validation of a High-Density 10 kV Silicon Carbide MOSFET Power Module with Reduced Electric Field Strength and Integrated Common-Mode Screen.

Degree: PhD, Electrical Engineering, 2019, Virginia Tech

URL: http://hdl.handle.net/10919/86596

► Electricity is the fastest-growing type of end-use energy consumption in the world, and its generation and usage trends are changing. Hence, the power electronics that… (more)

▼ Electricity is the fastest-growing type of end-use energy consumption in the world, and its generation and usage trends are changing. Hence, the power electronics that control the flow and conversion of electrical energy are an important research area. Advanced power electronics with improved efficiency, power density, reliability, and functionality are critical in data center, transportation, motor drive, renewable energy, and grid applications, among others. Wide-bandgap power semiconductors are enabling power electronics to meet these growing demands, and have thus begun appearing in commercial products, such as traction and solar inverters. Looking ahead, even greater strides can be made in medium-voltage systems due to the development of silicon carbide power devices with voltage ratings exceeding 10 kV. The ability of these devices to switch higher voltages faster and with lower losses than existing semiconductor technologies will drastically reduce the size, weight, and complexity of medium-voltage systems. However, these devices also bring new challenges for designers. This dissertation will present a package for 10 kV silicon carbide power MOSFETs that addresses the enhanced electric fields, greater electromagnetic interference, worsened dynamic imbalance, and higher heat flux issues associated with the packaging of these unique devices. Specifically, due to the low and balanced parasitic inductances, the power module prototype is able to switch at record speeds of tens of nanoseconds with negligible ringing and voltage overshoot. An integrated common-mode current screen contains the current that is generated by these fast voltage transients within the power module, rather than flowing to the system ground. This screen connection simultaneously increases the partial discharge inception voltage by reducing the electric field strength at the triple point of the insulating ceramic substrate. Further, field-grading plates are used in the bus bar to reduce the electric field strength at the module terminations. The heat flux is addressed by employing direct-substrate, jet-impingement cooling. The cooler is integrated into the module housing for increased power density. Advisors/Committee Members: Burgos, Rolando (committeechair), Boroyevich, Dushan (committeechair), Guido, Louis J. (committee member), Johnson, Mark (committee member), De La Reelopez, Jaime (committee member).

Subjects/Keywords: power electronics; silicon carbide; packaging; high voltage; electromagnetic interference

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APA (6^th Edition):

Dimarino, C. M. (2019). Design and Validation of a High-Density 10 kV Silicon Carbide MOSFET Power Module with Reduced Electric Field Strength and Integrated Common-Mode Screen. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/86596

Chicago Manual of Style (16^th Edition):

Dimarino, Christina Marie. “Design and Validation of a High-Density 10 kV Silicon Carbide MOSFET Power Module with Reduced Electric Field Strength and Integrated Common-Mode Screen.” 2019. Doctoral Dissertation, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/86596.

MLA Handbook (7^th Edition):

Dimarino, Christina Marie. “Design and Validation of a High-Density 10 kV Silicon Carbide MOSFET Power Module with Reduced Electric Field Strength and Integrated Common-Mode Screen.” 2019. Web. 28 Feb 2021.

Vancouver:

Dimarino CM. Design and Validation of a High-Density 10 kV Silicon Carbide MOSFET Power Module with Reduced Electric Field Strength and Integrated Common-Mode Screen. [Internet] [Doctoral dissertation]. Virginia Tech; 2019. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/86596.

Council of Science Editors:

Dimarino CM. Design and Validation of a High-Density 10 kV Silicon Carbide MOSFET Power Module with Reduced Electric Field Strength and Integrated Common-Mode Screen. [Doctoral Dissertation]. Virginia Tech; 2019. Available from: http://hdl.handle.net/10919/86596

Virginia Tech

23. Haryani, Nidhi. Zero Voltage Switching (ZVS) Turn-on Triangular Current Mode (TCM) Control for AC/DC and DC/AC Converters.

Degree: PhD, Electrical Engineering, 2020, Virginia Tech

URL: http://hdl.handle.net/10919/96397

► Power supplies are at the heart of today's advanced technological systems like aero planes, UAVs, electrical cars, uninterruptible power supplies (UPS), smart grids etc. These… (more)

Subjects/Keywords: rectifiers; inverters; zero voltage switching; critical conduction mode; triangular current mode; active power; reactive power

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APA (6^th Edition):

Haryani, N. (2020). Zero Voltage Switching (ZVS) Turn-on Triangular Current Mode (TCM) Control for AC/DC and DC/AC Converters. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/96397

Chicago Manual of Style (16^th Edition):

Haryani, Nidhi. “Zero Voltage Switching (ZVS) Turn-on Triangular Current Mode (TCM) Control for AC/DC and DC/AC Converters.” 2020. Doctoral Dissertation, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/96397.

MLA Handbook (7^th Edition):

Haryani, Nidhi. “Zero Voltage Switching (ZVS) Turn-on Triangular Current Mode (TCM) Control for AC/DC and DC/AC Converters.” 2020. Web. 28 Feb 2021.

Vancouver:

Haryani N. Zero Voltage Switching (ZVS) Turn-on Triangular Current Mode (TCM) Control for AC/DC and DC/AC Converters. [Internet] [Doctoral dissertation]. Virginia Tech; 2020. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/96397.

Council of Science Editors:

Haryani N. Zero Voltage Switching (ZVS) Turn-on Triangular Current Mode (TCM) Control for AC/DC and DC/AC Converters. [Doctoral Dissertation]. Virginia Tech; 2020. Available from: http://hdl.handle.net/10919/96397

Virginia Tech

24. Wen, Bo. Stability Analysis of Three-Phase AC Power Systems Based on Measured D-Q Frame Impedances.

Degree: PhD, Electrical Engineering, 2015, Virginia Tech

URL: http://hdl.handle.net/10919/51202

► Small-signal stability is of great concern for distributed power systems with a large number of regulated power converters. These converters are constant-power loads (CPLs) exhibit… (more)

▼ Small-signal stability is of great concern for distributed power systems with a large number of regulated power converters. These converters are constant-power loads (CPLs) exhibit a negative incremental input resistance within the output voltage regulation bandwidth. In the case of dc systems, design requirements for impedances that guarantee stability have been previously developed and are used in the design and specification of these systems. In terms of three-phase ac systems, a mathematical framework based on the generalized Nyquist stability criterion (GNC), reference frame theory, and multivariable control is set forth for stability assessment. However, this approach relies on the actual measurement of these impedances, which up to now has severely hindered its applicability. Addressing this shortcoming, this research investigates the small-signal stability of three-phase ac systems using measured d-q frame impedances. Prior to this research, negative incremental resistance is only found in CPLs as a results of output voltage regulation. In this research, negative incremental resistance is discovered in grid-tied inverters as a consequence of grid synchronization and current injection, where the bandwidth of the phase-locked loop determines the frequency range of the negative incremental resistance behavior, and the power rating of inverter determines the magnitude of the resistance. Prior to this research, grid synchronization stability issue and sub-synchronous oscillations between grid-tied inverter and its nearby rectifier under weak grid condition are reported and analyzed using characteristic equation of the system. This research proposes a more design oriented analysis approach based on the negative incremental resistance concept of grid-tied inverters. Grid synchronization stability issues are well explained under the framework of GNC. Although stability and its margin of ac system can be addressed using source and load impedances in d-q frame, method to specify the shape of load impedances to assure system stability is not reported. This research finds out that under unity power factor condition, three-phase ac system is decoupled. It can be simplified to two dc systems. Load impedances can be then specified to guarantee system stability and less conservative design. Advisors/Committee Members: Boroyevich, Dushan (committeechair), Burgos, Rolando (committeechair), Mattavelli, Paolo (committee member), Stilwell, Daniel J. (committee member), Roy, Christopher John (committee member).

Subjects/Keywords: Distributed power system; impedance; inverters; negative resistance circuits; Nyquist stability; rectifiers; power system stability; stability; synchronization

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APA (6^th Edition):

Wen, B. (2015). Stability Analysis of Three-Phase AC Power Systems Based on Measured D-Q Frame Impedances. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/51202

Chicago Manual of Style (16^th Edition):

Wen, Bo. “Stability Analysis of Three-Phase AC Power Systems Based on Measured D-Q Frame Impedances.” 2015. Doctoral Dissertation, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/51202.

MLA Handbook (7^th Edition):

Wen, Bo. “Stability Analysis of Three-Phase AC Power Systems Based on Measured D-Q Frame Impedances.” 2015. Web. 28 Feb 2021.

Vancouver:

Wen B. Stability Analysis of Three-Phase AC Power Systems Based on Measured D-Q Frame Impedances. [Internet] [Doctoral dissertation]. Virginia Tech; 2015. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/51202.

Council of Science Editors:

Wen B. Stability Analysis of Three-Phase AC Power Systems Based on Measured D-Q Frame Impedances. [Doctoral Dissertation]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/51202

Virginia Tech

25. Kim, Jong Wan. Back to Back Active Power Filter for Multi-Generator Power Architecture with Reduced dc-link Capacitor.

Degree: PhD, Electrical Engineering, 2020, Virginia Tech

URL: http://hdl.handle.net/10919/96638

► The transportation electrification has gained more and more attention due to its smaller carbon dioxide emission, better fuel efficiency. The recent advances in power devices,… (more)

Subjects/Keywords: harmonic elimination; 3 phase active power filter; multi-pulse converter; shipboard power system

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APA (6^th Edition):

Kim, J. W. (2020). Back to Back Active Power Filter for Multi-Generator Power Architecture with Reduced dc-link Capacitor. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/96638

Chicago Manual of Style (16^th Edition):

Kim, Jong Wan. “Back to Back Active Power Filter for Multi-Generator Power Architecture with Reduced dc-link Capacitor.” 2020. Doctoral Dissertation, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/96638.

MLA Handbook (7^th Edition):

Kim, Jong Wan. “Back to Back Active Power Filter for Multi-Generator Power Architecture with Reduced dc-link Capacitor.” 2020. Web. 28 Feb 2021.

Vancouver:

Kim JW. Back to Back Active Power Filter for Multi-Generator Power Architecture with Reduced dc-link Capacitor. [Internet] [Doctoral dissertation]. Virginia Tech; 2020. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/96638.

Council of Science Editors:

Kim JW. Back to Back Active Power Filter for Multi-Generator Power Architecture with Reduced dc-link Capacitor. [Doctoral Dissertation]. Virginia Tech; 2020. Available from: http://hdl.handle.net/10919/96638

Virginia Tech

26. Lee, Moonhyun. Digital-Based Zero-Current Switching (ZCS) Control Schemes for Three-Level Boost Power-Factor Correction (PFC) Converter.

Degree: PhD, Electrical Engineering, 2020, Virginia Tech

URL: http://hdl.handle.net/10919/99694

► Electronic-based devices and loads have been essential parts of modern society founded on rapid advancements of information technologies. Along with the progress, power supplying and… (more)

▼ Electronic-based devices and loads have been essential parts of modern society founded on rapid advancements of information technologies. Along with the progress, power supplying and charging of electronic products become routinized in daily lives, but still remain critical requisites for reliable operations. In many power-electronics-based supplying systems, ac-dc power-factor correction (PFC) circuits are generally located at front-end to feed back-end loads from universal ac-line sources. Since PFC stages have a key role in regulating ac-side current quality and dc-side voltage control, the importance of PFC performances cannot be emphasized enough from entire system point of view. Thus, advanced control schemes for PFC converters have been developed in quantity to achieve efficient operations and competent power qualities such as high power factor, low harmonic distortions and low electromagnetic interferences (EMI) noises. In this dissertation, a sort of PFC topologies named three-level boost (TLB) converter is chosen for target topology. Based on inherent three-level waveform capability of the topology, multiple zero-current switching (ZCS) control schemes are proposed. Compared to many conventional two-level PFC topologies, TLB PFC can provide additional degree-of-freedom to current modulation. The increased control flexibility can realize improvements of various waveform qualities including peak current stress, switching frequency range, harmonics and EMI amplitude. From the experimental results in this dissertation, improvements of waveform qualities in TLB PFC with the proposed schemes are verified with comparison to two-level current control schemes; in terms of efficiency, the results show that TLB PFC with the proposed schemes can have similar converter efficiency with conventional two-level boost converter in spite of increased component counts in the topology. Further, the proposed three-level control schemes can be utilized in adjustable forms to accomplish different control objectives depending on system characteristics and applications. In each chapter of this dissertation, a novel control scheme is proposed and explained with details of operation principle, key equations and digital implementation method. All the effectiveness of proposals and analyses are validated by a proper set of experimental results with a TLB PFC prototype. Advisors/Committee Members: Lai, Jih S. (committeechair), Stilwell, Daniel J. (committee member), Burgos, Rolando (committee member), Southward, Steve C. (committee member), Li, Qiang (committee member).

Subjects/Keywords: Three-Level Boost; Power-Factor Correction; Zero-Current Switching; Critical Conduction Mode; Discontinuous Conduction Mode; Spread-Spectrum Frequency Modulation; Electromagnetic Interference; Voltage Balancing

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APA (6^th Edition):

Lee, M. (2020). Digital-Based Zero-Current Switching (ZCS) Control Schemes for Three-Level Boost Power-Factor Correction (PFC) Converter. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/99694

Chicago Manual of Style (16^th Edition):

Lee, Moonhyun. “Digital-Based Zero-Current Switching (ZCS) Control Schemes for Three-Level Boost Power-Factor Correction (PFC) Converter.” 2020. Doctoral Dissertation, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/99694.

MLA Handbook (7^th Edition):

Lee, Moonhyun. “Digital-Based Zero-Current Switching (ZCS) Control Schemes for Three-Level Boost Power-Factor Correction (PFC) Converter.” 2020. Web. 28 Feb 2021.

Vancouver:

Lee M. Digital-Based Zero-Current Switching (ZCS) Control Schemes for Three-Level Boost Power-Factor Correction (PFC) Converter. [Internet] [Doctoral dissertation]. Virginia Tech; 2020. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/99694.

Council of Science Editors:

Lee M. Digital-Based Zero-Current Switching (ZCS) Control Schemes for Three-Level Boost Power-Factor Correction (PFC) Converter. [Doctoral Dissertation]. Virginia Tech; 2020. Available from: http://hdl.handle.net/10919/99694

Virginia Tech

27. Li, Bin. High Frequency Bi-directional DC/DC Converter with Integrated Magnetics for Battery Charger Application.

Degree: PhD, Electrical Engineering, 2018, Virginia Tech

URL: http://hdl.handle.net/10919/97874

► Due to the concerns regarding increasing fuel cost and air pollution, plug-in electric vehicles (PEVs) are drawing more and more attention. PEVs have a rechargeable… (more)

▼ Due to the concerns regarding increasing fuel cost and air pollution, plug-in electric vehicles (PEVs) are drawing more and more attention. PEVs have a rechargeable battery that can be restored to full charge by plugging to an external electrical source. However, the commercialization of the PEV is impeded by the demands of a lightweight, compact, yet efficient on-board charger system. Since the state-of-the-art Level 2 on-board charger products are largely silicon (Si)-based, they operate at less than 100 kHz switching frequency, resulting in a low power density at 3-12 W/in3, as well as an efficiency no more than 92 - 94% Advanced power semiconductor devices have consistently proven to be a major force in pushing the progressive development of power conversion technology. The emerging wide bandgap (WBG) material based power semiconductor devices are considered as game changing devices which can exceed the limit of Si and be used to pursue groundbreaking high frequency, high efficiency, and high power density power conversion. Using wide bandgap devices, a novel two-stage on-board charger system architecture is proposed at first. The first stage, employing an interleaved bridgeless totem-pole AC/DC in critical conduction mode (CRM) to realize zero voltage switching (ZVS), is operated at over 300 kHz. A bi-directional CLLC resonant converter operating at 500 kHz is chosen for the second stage. Instead of using the conventional fixed 400 V DC-link voltage, a variable DC-link voltage concept is proposed to improve the efficiency within the entire battery voltage range. 1.2 kV SiC devices are adopted for the AC/DC stage and the primary side of DC/DC stage while 650 V GaN devices are used for the secondary side of the DC/DC stage. In addition, a two-stage combined control strategy is adopted to eliminate the double line frequency ripple generated by the AC/DC stage. The much higher operating frequency of wide bandgap devices also provides us the opportunity to use PCB winding based magnetics due to the reduced voltage-second. Compared with conventional litz-wire based transformer. The manufacture process is greatly simplified and the parasitic is much easier to control. In addition, the resonant inductors are integrated into the PCB transformer so that the total number of magnetic components is reduced. A transformer loss model based on finite element analysis is built and used to optimize the transformer loss and volume to get the best performance under high frequency operation. Due to the larger inter-winding capacitor of PCB winding transformer, common mode noise becomes a severe issue. A symmetrical resonant converter structure as well as a symmetrical transformer structure is proposed. By utilizing the two transformer cells, the common mode current is cancelled within the transformers and the total system common mode noise can be suppressed. In order to charge the battery faster, the single-phase on-board charger concept is extended to a higher power level. By using the three-phase interleaved CLLC resonant… Advisors/Committee Members: Li, Qiang (committeechair), Burgos, Rolando (committee member), Centeno, Virgilio A. (committee member), Southward, Steve C. (committee member), Lee, Fred C. (committee member).

Subjects/Keywords: wide bandgap; high frequency; bi-direction; battery charger; resonant converter; PCB magnetic integration

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Li, B. (2018). High Frequency Bi-directional DC/DC Converter with Integrated Magnetics for Battery Charger Application. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/97874

Chicago Manual of Style (16^th Edition):

Li, Bin. “High Frequency Bi-directional DC/DC Converter with Integrated Magnetics for Battery Charger Application.” 2018. Doctoral Dissertation, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/97874.

MLA Handbook (7^th Edition):

Li, Bin. “High Frequency Bi-directional DC/DC Converter with Integrated Magnetics for Battery Charger Application.” 2018. Web. 28 Feb 2021.

Vancouver:

Li B. High Frequency Bi-directional DC/DC Converter with Integrated Magnetics for Battery Charger Application. [Internet] [Doctoral dissertation]. Virginia Tech; 2018. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/97874.

Council of Science Editors:

Li B. High Frequency Bi-directional DC/DC Converter with Integrated Magnetics for Battery Charger Application. [Doctoral Dissertation]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/97874

Virginia Tech

28. Wang, Jun. Switching-Cycle Control and Sensing Techniques for High-Density SiC-Based Modular Converters.

Degree: PhD, Electrical Engineering, 2018, Virginia Tech

URL: http://hdl.handle.net/10919/83518

► Nowadays high power density has become an emerging need for the medium-voltage (MV) high-power converters in applications of power distribution systems in urban areas and… (more)

▼ Nowadays high power density has become an emerging need for the medium-voltage (MV) high-power converters in applications of power distribution systems in urban areas and transportation carriers like ship, airplane, and so forth. The limited footprint or space resource cost such immensely high price that introducing expensive advanced equipment to save space becomes a cost-effective option. To this end, replacing conventional Si IGBT with the superior SiC MOSFET to elevate the power density of MV modular converters has been defined as the concentration of this research work. As the modular multilevel converter (MMC) is the most typical modular converter for high power applications, the research topic is narrowed down to study the SiC MOSFET-based MMC. Fundamentals of the MMC is firstly investigated by introducing a proposed state-space switching model, followed by unveiling all possible operation scenarios of the MMC. The lower-frequency energy fluctuation on passive components of the MMC is interpreted and prior-art approaches to overcome it are presented. By scrutinizing the converter's switching states, a new switching-cycle control (SCC) approach is proposed to balance the capacitor energy within one switching cycle is explored. An open-loop model-predictive method is leveraged to study the behavior of the SCC, and then a hybrid-current-mode (HCM) approach to realize the closed-loop SCC on hardware is proposed and verified in simulation. In order to achieve the hybrid-current-mode SCC (HCM-SCC), a high-performance Rogowski switch-current sensor (RSCS) is proposed and developed. As sensing the switching current is a critical necessity for HCM-SCC, the RSCS is designed to meet all the requirement for the control purposes. A PCB-embedded shielding design is proposed to improve the sensor accuracy under high dv/dt noises caused by the rapid switching transients of SiC MOSFET. The overall system and control validations have been conducted on a high-power MMC prototype. The basic unit of the MMC prototype is a SiC Power Electronics Building Block (PEBB) rated at 1 kV DC bus voltage. Owing to the proposed SCC, the PEBB development has achieved high power density with considerable reduction of passive component size. Finally, experimental results exhibit the excellent performance of the RSCS and the HCM-SCC. Advisors/Committee Members: Boroyevich, Dushan (committeechair), Burgos, Rolando (committeechair), De La Reelopez, Jaime (committee member), Wicks, Alfred L. (committee member), Lee, Fred C. (committee member).

Subjects/Keywords: High-density; SiC MOSFET; modular multilevel converter; switching-cycle control; Rogowski switch-current sensor

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Wang, J. (2018). Switching-Cycle Control and Sensing Techniques for High-Density SiC-Based Modular Converters. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/83518

Chicago Manual of Style (16^th Edition):

Wang, Jun. “Switching-Cycle Control and Sensing Techniques for High-Density SiC-Based Modular Converters.” 2018. Doctoral Dissertation, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/83518.

MLA Handbook (7^th Edition):

Wang, Jun. “Switching-Cycle Control and Sensing Techniques for High-Density SiC-Based Modular Converters.” 2018. Web. 28 Feb 2021.

Vancouver:

Wang J. Switching-Cycle Control and Sensing Techniques for High-Density SiC-Based Modular Converters. [Internet] [Doctoral dissertation]. Virginia Tech; 2018. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/83518.

Council of Science Editors:

Wang J. Switching-Cycle Control and Sensing Techniques for High-Density SiC-Based Modular Converters. [Doctoral Dissertation]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/83518

Virginia Tech

29. Zhang, Lujie. Load-Independent Class-E Power Conversion.

Degree: PhD, Electrical Engineering, 2020, Virginia Tech

URL: http://hdl.handle.net/10919/97601

► The Class-E topology was presented as a single-switch power amplifier with high efficiency at the optimum condition. Efficiency of a conventional Class-E design degrades with… (more)

▼ The Class-E topology was presented as a single-switch power amplifier with high efficiency at the optimum condition. Efficiency of a conventional Class-E design degrades with load variation dramatically due to the hard switching beyond the optimum conditions. Since two requirements need to be satisfied for soft switching in a conventional Class-E design, at least two parameters are tuned under load variation. Impressively, a load-independent Class-E inverter design was presented for maintaining Zero-Voltage-Switching (ZVS) and output voltage under a given load change without tuning any parameters, and it was validated with experimental results recently. A Thevenin model is established in this work to explain the realization of load-independency with fixed switching frequency and duty cycle. Based on that, a sequential design and tuning process is presented. A prototype switched at 6.78 MHz with 10-V input, 11.3-V output, and 22.5-W maximum output power was fabricated and tested to validate the theory. Soft switching is maintained with 3% output voltage variation while the output power is reduced tenfold. A load-independent ZVS Class-E inverter with constant current under load variation is then presented, by combining the presented design and a trans-susceptance network. The expectations were validated by a design switched at 6.78 MHz with 10-V input, 1.4-A output, and 12.6-W maximum output power. Soft switching is maintained with 16% output current varying over a 10:1 output power range. The load-independent Class-E design is extended to dc-dc converter by adding a diode rectifier bridge, inducing a varying capacitance. With the selected full-load compensation, ZVS is achieved at full load condition and slight non-ZVS occurs for the other load conditions. The expectation was validated by a dc-dc converter switched at 6.78 MHz with 11 V input, 12 V output, and 22 W maximum output power. ZVS (including slight non-ZVS) is maintained with 16% output voltage variation over 20:1 output power range. The varying capacitance in the Class-E dc-dc converter needs variable component to compensate. Thus, a Voltage Controlled Capacitor (VCC) is presented. The capacitance changes from 1 μF to 0.2 μF with a control voltage from 0 V to 25 V, resulting a 440% capacitance range. The capacitance range drops to only 40% with higher bias in the output voltage. Thus, a Linear Variable Capacitor (LVC) is presented, with 380% maximum capacitance range and less than 20% drop in the designed capacitor voltage range. Advisors/Committee Members: Ngo, Khai D. (committeechair), Southward, Steve C. (committee member), Ha, Dong S. (committee member), Burgos, Rolando (committee member), Manteghi, Majid (committee member).

Subjects/Keywords: Class-E inverter; Class-E dc-dc converter; load-independency; soft switching; constant output; variable capacitor

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Zhang, L. (2020). Load-Independent Class-E Power Conversion. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/97601

Chicago Manual of Style (16^th Edition):

Zhang, Lujie. “Load-Independent Class-E Power Conversion.” 2020. Doctoral Dissertation, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/97601.

MLA Handbook (7^th Edition):

Zhang, Lujie. “Load-Independent Class-E Power Conversion.” 2020. Web. 28 Feb 2021.

Vancouver:

Zhang L. Load-Independent Class-E Power Conversion. [Internet] [Doctoral dissertation]. Virginia Tech; 2020. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/97601.

Council of Science Editors:

Zhang L. Load-Independent Class-E Power Conversion. [Doctoral Dissertation]. Virginia Tech; 2020. Available from: http://hdl.handle.net/10919/97601

30. Chen, Fang. Control of DC Power Distribution Systems and Low-Voltage Grid-Interface Converter Design.

Degree: PhD, Electrical Engineering, 2017, Virginia Tech

URL: http://hdl.handle.net/10919/77532

► DC power distribution has gained popularity in sustainable buildings, renewable energy utilization, transportation electrification and high-efficiency data centers. This dissertation focuses on two aspects of… (more)

▼ DC power distribution has gained popularity in sustainable buildings, renewable energy utilization, transportation electrification and high-efficiency data centers. This dissertation focuses on two aspects of facilitating the application of dc systems: (a) system-level control to improve load sharing, voltage regulation and efficiency; (b) design of a high-efficiency interface converter to connect dc microgrids with the existing low-voltage ac distributions, with a special focus on common-mode (CM) voltage attenuation. Droop control has been used in dc microgrids to share loads among multiple sources. However, line resistance and sensor discrepancy deteriorate the performance. The quantitative relation between the droop voltage range and the load sharing accuracy is derived to help create droop design guidelines. DC system designers can use the guidelines to choose the minimum droop voltage range and guarantee that the sharing error is within a defined range even under the worst cases. A nonlinear droop method is proposed to improve the performance of droop control. The droop resistance is a function of the output current and increases when the output current increases. Experiments demonstrate that the nonlinear droop achieves better load sharing under heavy load and tighter bus voltage regulation. The control needs only local information, so the advantages of droop control are preserved. The output impedances of the droop-controlled power converters are also modeled and measured for the system stability analysis. Communication-based control is developed to further improve the performance of dc microgrids. A generic dc microgrid is modeled and the static power flow is solved. A secondary control system is presented to achieve the benefits of restored bus voltage, enhanced load sharing and high system efficiency. The considered method only needs the information from its adjacent node; hence system expendability is guaranteed. A high-efficiency two-stage single-phase ac-dc converter is designed to connect a 380 V bipolar dc microgrid with a 240 V split-phase single-phase ac system. The converter efficiencies using different two-level and three-level topologies with state-of-the-art semiconductor devices are compared, based on which a two-level interleaved topology using silicon carbide (SiC) MOSFETs is chosen. The volt-second applied on each inductive component is analyzed and the interleaving angles are optimized. A 10 kW converter prototype is built and achieves an efficiency higher than 97% for the first time. An active CM duty cycle injection method is proposed to control the dc and low-frequency CM voltage for grounded systems interconnected with power converters. Experiments with resistive and constant power loads in rectification and regeneration modes validate the performance and stability of the control method. The dc bus voltages are rendered symmetric with respect to ground, and the leakage current is reduced. The control method is generalized to three-phase ac-dc converters for larger power… Advisors/Committee Members: Boroyevich, Dushan (committeechair), Burgos, Rolando (committeechair), Baumann, William T. (committee member), Wicks, Alfred L. (committee member), Centeno, Virgilio A. (committee member).

Subjects/Keywords: dc power distribution; microgrid; droop control; load sharing; grid interface converter; single phase ac-dc

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APA (6^th Edition):

Chen, F. (2017). Control of DC Power Distribution Systems and Low-Voltage Grid-Interface Converter Design. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/77532

Chicago Manual of Style (16^th Edition):

Chen, Fang. “Control of DC Power Distribution Systems and Low-Voltage Grid-Interface Converter Design.” 2017. Doctoral Dissertation, Virginia Tech. Accessed February 28, 2021. http://hdl.handle.net/10919/77532.

MLA Handbook (7^th Edition):

Chen, Fang. “Control of DC Power Distribution Systems and Low-Voltage Grid-Interface Converter Design.” 2017. Web. 28 Feb 2021.

Vancouver:

Chen F. Control of DC Power Distribution Systems and Low-Voltage Grid-Interface Converter Design. [Internet] [Doctoral dissertation]. Virginia Tech; 2017. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/10919/77532.

Council of Science Editors:

Chen F. Control of DC Power Distribution Systems and Low-Voltage Grid-Interface Converter Design. [Doctoral Dissertation]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/77532

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