VTechWorks
VTechWorks provides global access to Virginia Tech scholarship, including journal articles, books, theses, dissertations, conference papers, slide presentations, technical reports, working papers, administrative documents, videos, images, and more by faculty, students, and staff. Faculty can deposit items to VTechWorks from Elements, including journal articles covered by the University open access policy. Email vtechworks@vt.edu for help.
Open Access Policy
Virginia Tech's open access policy enables researchers to deposit the accepted version of scholarly articles with no embargo.
Theses and Dissertations
Virginia Tech was first in the world to require ETDs in 1997, and continues to add scans of older theses and dissertations.
Open Textbooks
More than 40 freely available and openly licensed textbooks are among our most downloaded items.
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Recent Submissions
Estimation of Global Illumination using Cycle-Consistent Adversarial Networks
Oh, Junho; Abbott, A. Lynn (Springer, 2024-10-15)
Synthesis of realistic virtual environments requires careful rendering of light and shadows, a task often bottle-necked by the high computational cost of global illumination (GI) techniques. This paper introduces a new GI approach that improves computational efficiency without a significant reduction in image quality. The proposed system transforms initial direct-illumination renderings into globally illuminated representations by incorporating a Cycle-Consistent Adversarial Network (CycleGAN). Our CycleGAN-based approach has demonstrated superior performance over the Pix2Pix model according to the LPIPS metric, which emphasizes perceptual similarity. To facilitate such comparisons, we have created a novel dataset (to be shared with the research community) that provides in-game images that were obtained with and without GI rendering. This work aims to advance real-time GI estimation without the need for costly, specialized computational hardware. Our work and the dataset are made publicly available at https://github.com/junhofive/CycleGAN-Illumination.
Hybrid Multi-Level Inverter
(United States Patent Office)
This disclosure provides systems, methods, and apparatus for multi-level inverters. A hybrid binary cascaded multilevel inverter (BCMLI) is discussed that includes a plurality of H-bridge cells connected in a cascaded formation. DC input voltages of some of the H-bridge cells are provided by DC voltage sources. But inputs of other H-bridge cells coupled with capacitors instead. The H-bridge cells are operated to provide an AC output voltage at the output terminals of the inverter. One or more floating capacitor voltage controllers are used to vary one or more switching instances of the H-bridge cells such that a desirable level or charge is maintained across the one or more capacitors coupled with the input terminals of the H-bridge cells.
Hybrid Modulation Controlled DC-to-AC Converters
Aspects of hybrid modulation control for DC-to-AC converters are described. In one embodiment, a hybrid modulation pattern is generated. The hybrid modulation pattern separates switch gating control into multiple control regions for a half cycle of the waveform. A first control region modulates according to a first modulation technique and a second control region modulates according to a second modulation technique. The switches of a resonant converter are controlled according to the hybrid modulation pattern to generate the waveform.
Seamless Distributed Power Management of DC Microgrid under Cyber Attacks with Bidirectional Power Flow
Tran, Dat Thanh; Kim, Kyeong-Hwa; Lai, Jih-Sheng (IEEE, 2025)
A seamless distributed power management for the dc microgrid (DCMG) with bidirectional power flow is presented in this paper to achieve the overall system stabilization even under severe cyber attacks. First, a distributed secondary control (DSC) based on the V*-P droop curves is presented to ensure the power and voltage regulation for the DCMG system consisting of the electric vehicle (EV), wind turbine, battery, load, and utility grid agents under uncertain conditions. The proposed scheme automatically adjusts the utility grid droop curve to minimize electricity expenditure under electricity price change. To eliminate the negative effect of severe cyber attacks such as false data injection (FDI) and denial-of-service (DoS) in the distributed DCMG system, a resilient DSC based on the compensation term is utilized in the proposed scheme. In addition, by modifying the DSC structure of each power agent, the proposed scheme reduces the overshoot of the dc bus voltage even in the presence of the electricity price change, agent power variation, sudden utility grid disconnection, or critical state-of-charge (SOC) levels. Furthermore, the proposed distributed DCMG system utilizes only the unidirectional digital communication links (DCLs) to cut down the system cost and communication burden, which greatly simplifies communication structure. The efficiency and feasibility of the proposed distributed power management are validated by simulation and experimental results under various conditions.
Design of a 15kW High-Efficiency and High Power Density Bidirectional TCM Buck/Boost Converter
Hou, Zhengming; Jiao, Dong; Gutierrez, Bryan C.; Lai, Jih-Sheng; Chen, Po-Li (IEEE, 2024)
A non-isolated buck/boost converter features bidirectional power flow capability and a wide output voltage range. The zero-voltage switching (ZVS) can be achieved under triangular current mode (TCM) operation to achieve high power density and high efficiency. Most research has been conducted on TCM control strategies or low-power applications but rarely on the design of high-power TCM buck/boost converters. In this paper, a simplified inductor design methodology for the power conversion between a common dc bus and a wide-range variable dc voltage TCM buck/boost converter is proposed. A 15kW prototype is designed to regulate the voltage from 150V-1000V from a 1.1kV dc bus. The prototype demonstrates 16.36kW/L power density and 99.81% peak efficiency.