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Proceedings of the IEEE Dallas Circuits and systems Workshop (DCAS)

作者： Sai Pavan Kalakonda Mona Ghassemi Department of Electrical and Computer Engineering Zero Emission Realization of Optimized Energy Systems (ZEROES) Laboratory The University of Texas at Dallas Richardson TX USA

ISBN: (数字)9798350349535

ISBN: (纸本)9798350349542

Heat dissipation is one of the many problems that concerns all the electrical and electronic industries alike. On the other hand, with the ever-increasing demand for electrical energy the need for higher-rating power transformers (PTs) and their insulation has increased consistently over the years. The reliability of the PTs lies solely on the insulation inside them. With the conventional transformer oil and even with its biodegradable replacements, PTs became very bulky. A one-stop solution to deal with bulkiness, heat dissipation, and electrical insulation is the recently innovated nanodielectric fluids. Nanodielectric fluid (NDF) is a nanofluid (NF) whose base fluid has dielectric properties. The extensive research happening in this field confirms that the nanodielectric fluids have enhanced thermal as well as dielectric properties with which the bulkiness of the PTs can be decreased. A critical review of the NDFs investigated for their potential replacement of traditional transformer oil is presented in this paper. This paper presents the latest developments on this topic, identifies technical gaps, and can be used as a useful resource and framework for future research.

关键词： Fluids Reviews Oils Oil insulation Hybrid power systems Dielectrics Thermal stability

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NASA N3-X Aircraft DC Power System Design

NASA N3-X Aircraft DC Power System Design

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Proceedings of the IEEE Dallas Circuits and systems Workshop (DCAS)

作者： Farzana Islam Mona Ghassemi Department of Electrical and Computer Engineering Zero Emission Realization of Optimized Energy Systems (ZEROES) Laboratory The University of Texas at Dallas Richardson TX USA

ISBN: (数字)9798350349535

ISBN: (纸本)9798350349542

The increasing demand for air travel and the greenhouse gas (GHG) pollution related to the aviation industry is a major concern that needs to be resolved to achieve net zero emissions. More-electric aircraft (MEA) and all-electric aircraft (AEA) are viable solutions to mitigate this but for their electric power systems (EPSs) which have been targeted as medium-voltage direct current (MVDC) very few power flow analyses exist. In this article, the hybrid NASA N3-X aircraft is redesigned by introducing electrochemical energy units (EEUs) instead of two turboshaft engines to supply the aircraft” EPS. The power flow analysis is carried out for a proposed MVDC EPS architecture for the cruising time compared to that during takeoff to determine the maximum currents flowing different branches of the proposed architecture. The results obtained in this paper are vital since they are needed for designing MVDC aircraft power cables capable of working at both takeoff conditions under almost atmospheric pressure and during cruising time conditions where the maximum current flowing through cables decreases due to limited convection heat transfer due to low pressure.

关键词： Pollution Power cables Net zero NASA Voltage Medium voltage Power systems

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Accurate, provable, and fast nonlinear tomographic reconstruction: A variational inequality approach

arXiv

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arXiv 2025年

作者： Lou, Mengqi Verchand, Kabir Aladin Fridovich-Keil, Sara Pananjady, Ashwin Georgia Institute of Technology School of Industrial and Systems Engineering United States School of Electrical and Computer Engineering United States University of Cambridge Statistical Laboratory United Kingdom Stanford University Department of Electrical Engineering United States

We consider the problem of signal reconstruction for computed tomography (CT) under a nonlinear forward model that accounts for exponential signal attenuation, a polychromatic X-ray source, general measurement noise (e.g. Poisson shot noise), and observations acquired over multiple wavelength windows. We develop a simple iterative algorithm for single-material reconstruction, which we call EXACT (EXtragradient Algorithm for Computed Tomography), based on formulating our estimate as the fixed point of a monotone variational inequality. We prove guarantees on the statistical and computational performance of EXACT under practical assumptions on the measurement process. We also consider a recently introduced variant of this model with Gaussian measurements, and present sample and iteration complexity bounds for EXACT that improve upon those of existing algorithms. We apply our EXACT algorithm to a CT phantom image recovery task and show that it often requires fewer X-ray projection exposures, lower source intensity, and less computation time to achieve similar reconstruction quality to existing methods. © 2025, CC BY.

关键词： computerized tomography

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A Comparative Study on Partial Discharge and Dielectric Strength of MMEI Flat Samples under AC and DC Conditions at Atmospheric Pressure

A Comparative Study on Partial Discharge and Dielectric Stre...

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IEEE Green Energy and systems Conference (IGESC)

作者： Saikat Chowdhury Anoy Saha Md Asifur Rahman Mona Ghassemi Department of Electrical and Computer Engineering Zero Emission Realization of Optimized Energy Systems (ZEROES) Laboratory The University of Texas at Dallas Richardson TX USA

ISBN: (数字)9798350379617

ISBN: (纸本)9798350379624

The shift towards electrifying transportation systems has become a pivotal strategy in achieving net-zero emissions, driving extensive adoption across the transportation sector. Consequently, the aviation industry is transitioning to all-electric aircraft (AEA). For AEA, an electric power system (EPS) that delivers high power while maintaining low system mass is crucial. Cables are vital components in this future EPS, and one way to reduce their weight is by operating at higher voltages. However, designing insulation systems for higher voltages poses challenges due to increased partial discharge (PD) activity in harsh aviation environments characterized by extremely low pressures and moisture levels. To address these challenges, multilayer multifunction electrical insulation (MMEI) systems have been developed, offering higher breakdown strength compared to single-layer insulation systems. Our previous study proposed some novel MMEI designs for medium voltage direct current (MVDC) power cables capable of operating at low pressures. In this paper, the PD characteristics of these designed MMEI systems are analyzed using the OMICRON MPD 800 under both AC and DC conditions on flat samples. Additionally, the dielectric strength for AC and DC is tested and compared using the Weibull distribution method.

关键词： Partial discharges Insulation Breakdown voltage Transportation Power system stability Discharges (electric) Weibull distribution Aircraft Stress Standards

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Statistical Effects of Propagation Environment and Transmit Array Topology on Cell-Edge User Service Quality at mm-Waves

Statistical Effects of Propagation Environment and Transmit ...

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European Conference on Antennas and Propagation, EuCAP

作者： Nicolas Van De Kreeke Yanki Aslan Nehir Berk Onat Alexander Yarovoy Department of Microelectronics Microwave Sensing Signals and Systems Group Faculty of Electrical Engineering Mathematics and Computer Science Delft University of Technology Delft The Netherlands

The effects of multipath on the statistical cell-edge user service quality is for the first time investigated for mm-wave multi-user communication systems. The focus is given on setting the user spacing constraints and the transmit array topology via thinning, which can be used to enhance wireless security or decrease analog/digital complexity. A hybrid line-of-sight/non-line-of-sight channel is created by using a statistical model following the communication standards. The multipath signal components are included in the model by using non-coherent or coherent modes of operation. It is shown in simulation that selection, by the medium access control layer, of large angular spacings between the simultaneously served users and application of antenna array thinning at the array edges improves the system performance.

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Influence of Rise Time on the Aging of Electric Machine Windings

Influence of Rise Time on the Aging of Electric Machine Wind...

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Conference on electrical Insulation and Dielectric Phenomena, (CEIDP)

作者： Easir Arafat Md Asifur Rahman Farzana Islam Mona Ghassemi Department of Electrical and Computer Engineering Zero Emission Realization of Optimized Energy Systems (ZEROES) Laboratory The University of Texas at Dallas Richardson TX USA

ISBN: (数字)9798350366679

ISBN: (纸本)9798350366686

This study examines how fast rise times, which are common in modern power electronics and drive systems, affect the aging of electric machine windings. It focuses on how to ensure these windings can last longer and work reliably in electrical systems. A twisted pair magnet wire with insulation commonly used in wound machines was used to get experimental data to understand how different voltage waveforms can influence endurance testing of motor insulation systems powered by inverters. Unlike past studies that looked at comparatively slower rise times and fewer repetitions, this research specifically addresses the challenges posed by next-generation wide bandgap (WBG)-based conversion systems. These systems operate at very high speeds, up to 100 kV/μs, and switch frequencies up to 500 kHz, where both frequency and rise time are crucial factors affecting insulation aging over time.

关键词： Insulation Time-frequency analysis Electric machines Windings Voltage Switches Aging Reliability engineering Wire Testing

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Location of Shield Wires for Unconventional High Capacity Transmission Lines

Location of Shield Wires for Unconventional High Capacity Tr...

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Proceedings of the IEEE Dallas Circuits and systems Workshop (DCAS)

作者： Saikat Chowdhury Babak Porkar Mona Ghassemi Department of Electrical and Computer Engineering Zero Emission Realization of Optimized Energy Systems (ZEROES) Laboratory The University of Texas at Dallas Richardson TX USA

ISBN: (数字)9798350349535

ISBN: (纸本)9798350349542

To achieve net-zero emission in America by 2050, high voltage transmission capacity must expand ~60% by 2030 and triple by 2050 to connect further wind and solar facilities to demand. This expansion requires a capital investment in transmission capacity of $360 billion by 2030 and $2.4 trillion by 2050. Considering the high cost of building transmission lines, innovations toward high-capacity overhead lines have been targeted to reduce the number of transmission lines required. In our previous studies, we introduced unconventional high-capacity transmission lines. To realize these novel transmission lines, various aspects of line design should be studied, and this paper addresses determining the location and number of shield wires to protect these novel lines against lightning strikes. Lightning-induced overvoltage across line insulators is one of the key factors in power system outages. The design meets the shielding failure flashover rate (SFFOR) $\leq 0.05/100$ km-years for all three phases of the unconventional high-capacity transmission line. Brown-Whitehead equations were used to measure and analyze the striking distance for vertical strokes.

关键词： Technological innovation Power transmission lines Net zero Wires Lightning Flashover Transmission line measurements

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High Power Density, Cost-Effective HVDC Cables for Power Transmission on the Moon

High Power Density, Cost-Effective HVDC Cables for Power Tra...

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IEEE Texas Power and Energy Conference (TPEC)

作者： Anoy Saha Mona Ghassemi Department of Electrical and Computer Engineering Zero Emission Realization of Optimized Energy Systems (ZEROES) Laboratory The University of Texas at Dallas Richardson TX USA

The need for lunar surface power is expected to grow to megawatt levels, which is in line with NASA's objective of building a long-term human presence on the moon that can house more than 100 people. As humanity seeks to establish a long-term presence on the moon and construct lunar habitats or bases, the importance of efficient and dependable power transmission on the moon becomes crucial. Power lines of varied lengths and power transfer capacities are needed for a lunar-based power system to link the various power generation, energy storage, and load facilities dispersed over the lunar surface. Developing power lines with high power density, while considering weight, volume, safety, cost-effectiveness, and reliability in the harsh lunar environment, poses a significant challenge. Three potential locations for power lines on the lunar surface can be considered: above the surface, on the surface, or below the surface. The extreme lunar environment, characterized by factors such as temperature variation, micrometeoroid bombardment, and ionizing radiation, limits the effectiveness of the first two methods for power transfer on the moon. Underground deployment offers both safety and convenience. Using the COMSOL Multiphysics software, this work proposes a novel method for designing and assessing affordable bipolar HVDC cables for power transmission below the lunar surface with an emphasis on its electrical insulation difficulties. At a voltage level of up to ±10 kV, the cables are intended to transfer power at two different levels: medium power (500 kW), and high power (1 MW). These specially designed cables offer a viable solution for power transmission on the moon, as they are capable of functioning effectively in harsh lunar conditions.

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MVDC Bipolar Power Cables with Rectangular Geometry Design for Envisaged All-Electric Wide-Body Aircraft

MVDC Bipolar Power Cables with Rectangular Geometry Design f...

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IEEE Texas Power and Energy Conference (TPEC)

Designing power cables that provide high power and low system mass is one of the major goals in achieving the future all-electric wide-body aircraft. Radiative and convective heat transfers from a cable's surface to the surrounding air determine how much current is permitted to flow through it. At a cruising altitude of 12.2 km (18.8 kPa) for wide-body aircraft, the limited heat transfer by convection poses thermal issues for the design of aircraft cables. These thermal challenges are exacerbated for bipolar electric power systems (EPS), which are usually made up of two power lines next to each other. The cable's surface area affects both convective and radiative heat transfers. Changing the shape of the cable is one technique to improve heat transfers and compensate for the reduced convective heat transfer caused by low air pressure. In comparison to cylindrical and cuboid cables, the rectangular geometry design gives a bigger contact area with the surrounding atmosphere for the same cross-section area, hence it is anticipated that the heat transfer would rise and as a result, the cable's maximum power-carrying capability will be higher. The purpose of this paper is to design ±5 kV bipolar MVDC power cables with rectangular geometry to raise the maximum current carrying capacity of the cable and analyze its performance with bipolar cylindrical and cuboid geometries.

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A Review of Insulation Challenges and Mitigation Strategies in (U)WBG Power Modules Packaging

A Review of Insulation Challenges and Mitigation Strategies ...

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IEEE Texas Power and Energy Conference (TPEC)

作者： Pujan Adhikari Mona Ghassemi Department of Electrical and Computer Engineering Zero Emission Realization of Optimized Energy Systems (ZEROES) Laboratory The University of Texas at Dallas Richardson TX USA

In the ever-growing landscape of electrical power demand, the future of power electronics module packaging lies in the realm of wide-bandgap (WBG) materials, including silicon carbide (SiC), gallium nitride (GaN), and cutting-edge ultra WBG (UWBG) materials like diamond, aluminum nitride (AlN), and hexagonal-boron nitride (h-BN). These materials offer superior properties to traditional silicon-based devices, promising higher power density, reduced weight, and increased operating temperature, voltage, and frequency. However, pushing the boundaries for power electronics modules presents challenges in insulation systems as the encapsulation material and the ceramic substrate may not withstand the functional parameters, potentially leading to unfavorable conditions like high field stress and partial discharge (PD), ultimately resulting in insulation failure. This paper presents a thorough analysis of the characteristics of the electrical insulation materials used in power electronics devices based on the research in WBG packaging conducted in recent years. The significance of maximum electric field stress at triple points (TPs) is examined. Furthermore, the paper reviews the strategies and techniques employed to mitigate the challenges related to maximum field stress and PDs in both encapsulation and substrate materials. It is concluded that the mitigation strategies are promising in improving insulation systems for packaging, but the studies lack their implementation under actual operating conditions of WBG power modules.

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