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15th International Conference on Information and Communication Technology Convergence, ICTC 2024

作者： Nam, Hyunwoo Kim, Gyu Seon Kim, Joongheon Inha University Department of Industrial Management Engineering Incheon Korea Republic of Korea University Department of Electrical and Computer Engineering Seoul Korea Republic of

ISBN: (纸本)9798350364637

This research examines the role of public bicycle systems in reducing carbon emissions, which significantly contribute to global warming. Centered in Seoul, South Korea-a city with some of the highest carbon dioxide emissions among global metropolises-this study seeks to improve the city's shared bicycle services to address environmental challenges. The analysis is based on five primary datasets. Data on public bicycle usage, new subscriber data, master information data, bicycle road data, and weather data. These datasets identify patterns in user behavior, particularly across various age demographics, and the relationship between bicycle infrastructure and rental volume. The findings highlight that better access to bicycle lanes and more rental stations are crucial in encouraging bicycle use. Additionally, a random forest (RF)-based predictive model is constructed to estimate bicycle rental volume using weather data, achieving a mean absolute error (MAE) of 5.21. The outcomes suggest that strategically enhancing bicycle infrastructure and implementing predictive rental services can significantly boost public bicycle usage, thereby helping to lower urban carbon emissions. Further researches are recommended to broaden data collection across diverse geographical areas and refine predictive models to enhance the effectiveness of public bicycle systems. © 2024 IEEE.

关键词： Carbon capture and utilization

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Voltage and Current Dynamics-Canceled Virtual Synchronous Generators for Stability Guarantee

Voltage and Current Dynamics-Canceled Virtual Synchronous Ge...

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2023 IEEE PES Innovative Smart Grid Technologies - Asia, ISGT Asia 2023

作者： Zhou, Weihua Mohammed, Nabil Bahrani, Behrooz Monash University Department of Electrical and Computer Systems Engineering Melbourne Australia

ISBN: (纸本)9798350327748

The virtual synchronous generator (VSG) is an attractive grid-forming technique that emulates the swing equation of conventional synchronous generators, and can compensate for the power grid's weakened inertia and damping caused by the widespread use of phase-locked-loop-based grid-following inverters. However, the interaction between the VSG's active power control (APC) and strong grids can lead to low-frequency oscillations, which jeopardizes the VSG's safe and reliable operation. To address this issue, this paper proposes a novel VSG control strategy that utilizes a voltage and current dynamics cancellation (VCDC) module. The VCDC module reshapes the VSG's impedance model, achieving symmetry, operating point independence, APC parameters independence, and low-frequency passivity. Simulation results demonstrate the effectiveness of the proposed VCDC module in stabilizing the VSG with fixed APC parameters under full power transfer and ultra strong grids. © 2023 IEEE.

关键词： Synchronous generators

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Solving non-cyclic dynamic multi-objective optimization problems via GRU prediction and multi-information hybrid exploration

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Journal of Supercomputing 2025年第8期81卷 1-34页

作者： Sun, Hao Bai, Xiaochuang Wang, Cong Yang, He Hu, Ziyu School of Electrical and Engineering Yanshan University Hebei Qinhuangdao066004 China Key Laboratory of Industrial Computer Control Engineering of Hebei Province Yanshan University Hebei Qinhuangdao066004 China Electrical automation department Tianjin Research Institute of Electric Science Co. Ltd. Tianjin China

In non-cyclic dynamic multi-objective optimization problems, the non-cyclic nature of environmental changes may cause the Pareto optimal front (PF) to be different from historical times. In addition, changes may also occur on the Pareto optimal solutions set (PS). However, predictions based solely on a single space show lower accuracy due to insufficient information. Therefore, solving non-cyclic dynamic multi-objective optimization problems via gate recurrent unit (GRU) prediction and multi-information hybrid exploration (GPMHE) is designed to overcome the above challenges. In the objective space, the GRU-based prediction strategy (GP) captures patterns of population change, predicts its distribution in new environments, and subsequently maps the results to the decision space;The multi-information hybrid exploration strategy (MHE) takes the feature individual as the representative individual, adaptively guides the population evolution direction in the decision space, thereby enhancing the algorithm’s adaptability. Compared with five advanced algorithms on the non-cyclic dynamic benchmark test set (NCD), the proposed algorithm GPMHE has shown robust adaptation to dynamic environmental changes. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.

关键词： Multiobjective optimization

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Cross-Coupling Effects of Voltage Control and Active Power Control on Small-Signal Stability of Virtual Synchronous Generator 11

Cross-Coupling Effects of Voltage Control and Active Power C...

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11th International Conference on Power Electronics - ECCE Asia, ICPE 2023-ECCE Asia

作者： Xu, Jingzhe Zhou, Weihua Bahrani, Behrooz Monash University Department of Electrical and Computer Systems Engineering Melbourne Australia

ISBN: (纸本)9788957083505

Inverter-based renewable energy resources, as a critical response to the net-zero energy transition, have been displacing conventional synchronous generation. However, this displacement has increased the grid's vulnerability to disturbances. The virtual synchronous generator (VSG) is a potential solution for grid strengthening. However, previous research has shown that VSG can also experience instability under certain grid conditions, which have been partially addressed in previous work. This paper aims to fill the gaps in these works by exploring the fundamental causation of instability through an updated comprehensive state-space modeling, parameter scanning, and consequent states participation factor analysis. It has been found that both voltage and active power controllers contribute to low-frequency instabilities in most cases. Furthermore, the two controllers are tightly coupled, although parameterising may improve decoupling. © 2023 The Korean Institute of Power Electronics.

关键词： Synchronous generators

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Modelling of stress development in high pre-load filament banding of high-speed rotors for PMSM applications

Modelling of stress development in high pre-load filament ba...

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2023 IEEE Energy Conversion Congress and Exposition, ECCE 2023

作者： Wong, Kelvin Klink, David Heins, Greg Bahrani, Behrooz Monash University Department of Electrical and Computer Systems Engineering Melbourne Australia

ISBN: (纸本)9798350316445

Increasing the permissible operating speed of permanent magnet electric machines (PMSM) presents a range of intrinsic benefits. This however also raises a myriad of challenges associated with high-speed operation, including rotor burst. One solution is the use of filament wound rotor sleeves. The present work brings to attention the importance of understanding the rotor and band stress state in filament banded rotors. An analytical model was developed which captures the effects of winding tension and rotor stiffness. This model will be experimentally validated through in-situ stress measurement during filament winding. A basic optimisation approach for the parameters of winding tension and layer count are proposed, which result in an increase in the maximum operating speed without altering the sleeve material or geometry. This type of modelling which considers the interaction between banding configuration and rotor geometry can be further extended to describe complex rotor stack-up and non-uniform stress development. © 2023 IEEE.

关键词： analytical method carbon fiber sleeve high-speed mechanical stress permanent magnet machines rotor strength analysis

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Mutative Evolution for Calculating Maximally Localized Wannier Functions in Photonic Crystals

Mutative Evolution for Calculating Maximally Localized Wanni...

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2024 Conference on Lasers and Electro-Optics/Pacific Rim, CLEO-PR 2024

作者： Lee, Dayeong Lee, Gitae Park, Seungkyun Park, Hyungchul Park, Namkyoo Yu, Sunkyu Intelligent Wave Systems Laboratory Department of Electrical and Computer Engineering Seoul National University Seoul08826 Korea Republic of Photonic Systems Laboratory Department of Electrical and Computer Engineering Seoul National University Seoul08826 Korea Republic of

We propose a neuroevolutionary algorithm to calculate maximally localized Wannier functions in photonic crystals, as an alternative method of conventional gradient-based approaches. © 2024 The Author(s)

关键词： Photonic crystals

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The Group Robustness is in the Details: Revisiting Finetuning under Spurious Correlations 38

The Group Robustness is in the Details: Revisiting Finetunin...

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38th Conference on Neural Information Processing systems, NeurIPS 2024

作者： LaBonte, Tyler Hill, John C. Zhang, Xinchen Muthukumar, Vidya Kumar, Abhishek H. Milton Stewart School of Industrial and Systems Engineering Georgia Institute of Technology United States School of Electrical and Computer Engineering Georgia Institute of Technology United States Google DeepMind United Kingdom

Modern machine learning models are prone to over-reliance on spurious correlations, which can often lead to poor performance on minority groups. In this paper, we identify surprising and nuanced behavior of finetuned models on worst-group accuracy via comprehensive experiments on four well-established benchmarks across vision and language tasks. We first show that the commonly used class-balancing techniques of mini-batch upsampling and loss upweighting can induce a decrease in worst-group accuracy (WGA) with training epochs, leading to performance no better than without class-balancing. While in some scenarios, removing data to create a class-balanced subset is more effective, we show this depends on group structure and propose a mixture method which can outperform both techniques. Next, we show that scaling pretrained models is generally beneficial for worst-group accuracy, but only in conjunction with appropriate class-balancing. Finally, we identify spectral imbalance in finetuning features as a potential source of group disparities - minority group covariance matrices incur a larger spectral norm than majority groups once conditioned on the classes. Our results show more nuanced interactions of modern finetuned models with group robustness than was previously known. Our code is available at https://***/tmlabonte/revisiting-finetuning. © 2024 Neural information processing systems foundation. All rights reserved.

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Improved Retrieval of Effective Parameters in Hyperbolic Metamaterials for Oblique Incidence 16

Improved Retrieval of Effective Parameters in Hyperbolic Met...

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16th Pacific Rim Conference on Lasers and Electro-Optics, CLEO-PR 2024

作者： Park, Jusung Park, Seungkyun Kim, Kyuho Yu, Sunkyu Park, Namkyoo Seoul National University Photonic Systems Laboratory Department of Electrical and Computer Engineering Seoul08826 Korea Republic of Seoul National University Intelligent Wave Systems Laboratory Department of Electrical and Computer Engineering Seoul08826 Korea Republic of

An improved retrieval method for effective permittivity and permeability of hyperbolic metamaterials at oblique incidence is presented. We revisit a branching problem at oblique incidence. © 2024 The Authors OCIS...

ISBN: (纸本)9798350372076

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Accurate and Approximate Solutions of Nonlinear Electron Plasma Oscillations

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International Journal of Applied and Computational Mathematics 2024年第4期10卷 1-24页

作者： Kontomaris, S.V. Malamou, A. Faculty of Engineering and Architecture Metropolitan College BioNanoTec LTD Radar Systems and Remote Sensing Lab of School of Electrical and Computer Engineering of National Technical University of Athens

Nonlinear oscillations can be used to describe a significant number of physical phenomena from classic to modern physics. Thus, it is important to find accurate solutions using elementary functions that can be easily applied in relative applications. In this paper, the oscillations described by the nonlinear differential equation u^′′=ω_p0²(1-u∓2β²u^γ), where ω_p0,β,γ are positive constants are being considered. The aforementioned differential equations are of great importance since they are used to describe electron plasma oscillations under the influence of temperature effects and for big oscillations amplitudes. The amplitude and period of the oscillation for different values of constants β,γ are derived using rigorous mathematical analysis and simplified approximate methods. In addition, accurate solutions u=f(t) in the form of elementary functions are also presented. The results of this paper can be also applied to similar cases in physics (e.g. classic mechanics) where differential equations of the same form apply. © The Author(s), under exclusive licence to Springer Nature India Private Limited 2024.

关键词： Nonlinear differential equations Nonlinear oscillation’s period Plasma physics Thermal effects

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Impacts of the Reactive Power Control on the Small-signal Stability of Grid Forming Inverters

Impacts of the Reactive Power Control on the Small-signal St...

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2023 IEEE PES Innovative Smart Grid Technologies - Asia, ISGT Asia 2023

作者： Mohammed, Nabil Zhou, Weihua Bahrani, Behrooz Monash University Department of Electrical and Computer Systems Engineering Melbourne Australia

ISBN: (纸本)9798350327748

Grid forming inverters (GFMIs) are emerging as promising alternatives to address grid instability challenges, offering vital ancillary services to power systems, including inertia support, frequency support, and oscillation damping. Therefore, understanding the control mechanisms and stability characteristics of GFMIs is crucial. This study investigates two control approaches for regulating the output reactive power used by virtual synchronous generator (VSG)-based GFMIs. The first method (without reactive power controller (without RPC)) sets the voltage reference for the voltage loop as a constant value pre-computed using power flow equations, while the second method (with RPC) explicitly specifies the desired reactive power and automatically generates the voltage reference for the voltage loop. This study thoroughly examines the robustness of these two control methods under varying grid conditions using frequency domain analysis (Bode and Nyquist plots) and time domain verification based on the EMT model simulated in MATLAB/Simulink to analyze small-signal stability and low-frequency oscillations. Additionally, this study offers recommendations for enhanced stability, highlighting the importance of selecting the appropriate reactive power control strategy for VSG-based GFMIs, particularly in strong grids, to ensure stable and reliable grid operation. © 2023 IEEE.

关键词： Stability

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