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Publicações

2024

The impact of V2G charging stations (active power electronics) to the higher frequency grid impedance

Autores
Grasel, B; Baptista, J; Tragner, M;

Publicação
SUSTAINABLE ENERGY GRIDS & NETWORKS

Abstract
Renewable energy generation technologies, heat pumps or electric vehicle (EV) charging stations use active power electronics such as IGBT or MOSFET for AC to DC conversion with the consequence of emissions in the higher frequency range above 2 kHz (non-intentional supraharmonic emissions) and with an impact to the higher frequency grid impedance. In this study the impact of active power electronics on the higher frequency grid impedance in the range up to 150 kHz is analyzed. As existing grid modelling solutions do not consider these technologies sufficiently, this study analyzes the impact of a vehicle to grid (V2G) chargers to a representative distribution grid considering different grid topologies and different types of V2G chargers. The study shows that the additional capacitance and inductance (LCL filter, DC link capacitor) introduced in the electrical grid causes parallel and series resonances in a wide frequency range starting from 500 Hz up to 50 kHz. The grid topology and the number of V2G chargers connected determines the frequency range and characteristics of resonances. Finally, the major contribution of this study is outlining the importance of considering the higher frequency grid impedance for characterization of supraharmonic emissions (primary vs. secondary emissions) and their propagation.

2024

Virtual Batteries Business Models for Energy Suppliers

Autores
Gomes, I; Sousa, JVJ; Sousa, J; Lucas, A;

Publicação
2024 20TH INTERNATIONAL CONFERENCE ON THE EUROPEAN ENERGY MARKET, EEM 2024

Abstract
Self-consumption regulations are leading to the emergence of new business models proposed by new players and causing traditional players to make new proposals to take advantage of the new business opportunities. In this context, traditional retailers are assessing self-consumption business models, offering management services for self-consumption structures, or the installation of distributed resources, such as solar panels or batteries. Some of the new business models being proposed by electricity suppliers are related to virtual battery services. Indeed, suppliers can, in the free retail market, create innovative tariffs, and design them to make their customers believe they own and manage a battery, even if it does not correspond to a physical battery in the grid. This paper analyses the business model of a supplier offering a virtual battery service, comparing it to the installation of a physical battery, showing that it has no significant benefits compared to more simple approaches.

2024

More (Enough) Is Better: Towards Few-Shot Illegal Landfill Waste Segmentation

Autores
Molina, M; Veloso, B; Ferreira, CA; Ribeiro, RP; Gama, J;

Publicação
ECAI 2024 - 27th European Conference on Artificial Intelligence, 19-24 October 2024, Santiago de Compostela, Spain - Including 13th Conference on Prestigious Applications of Intelligent Systems (PAIS 2024)

Abstract
Image segmentation for detecting illegal landfill waste in aerial images is essential for environmental crime monitoring. Despite advancements in segmentation models, the primary challenge in this domain is the lack of annotated data due to the unknown locations of illegal waste disposals. This work mainly focuses on evaluating segmentation models for identifying individual illegal landfill waste segments using limited annotations. This research seeks to lay the groundwork for a comprehensive model evaluation to contribute to environmental crime monitoring and sustainability efforts by proposing to harness the combination of agnostic segmentation and supervised classification approaches. We mainly explore different metrics and combinations to better understand how to measure the quality of this applied segmentation problem.

2024

Comparison between LightGBM and other ML algorithms in PV fault classification

Autores
Monteiro, P; Lino, J; Araújo, RE; Costa, L;

Publicação
EAI Endorsed Trans. Energy Web

Abstract
In this paper, the performance analysis of Machine Learning (ML) algorithms for fault analysis in photovoltaic (PV) plants, is given for different algorithms. To make the comparison more relevant, this study is made based on a real dataset. The goal was to use electric and environmental data from a PV system to provide a framework for analysing, comparing, and discussing five ML algorithms, such as: Multilayer Perceptron (MLP), Decision Tree (DT), K-Nearest Neighbors (KNN), Support Vector Machine (SVM) and Light Gradient Boosting Machine (LightGBM). The research findings suggest that an algorithm from the Gradient Boosting family called LightGBM can offer comparable or better performance in fault diagnosis for PV system.

2024

Nyon-Data, a Fall Detection Dataset from a Hinged Board Apparatus

Autores
Dionísio, RP; Rosa, AR; Jesus, CSDS;

Publicação
Lecture Notes in Networks and Systems

Abstract
Falls are one of the causes of severe hilliness among elders, and the COVID-19 pandemic increased the number of unattended cases because of the social distancing measures. This study aims to create a dataset that collects the data from a 3-axis acceleration sensor fixed on a hinged board apparatus that mimics a human fall event. The datalogging system uses off-the-shelf devices to measure, collect and store the data. The resulting dataset includes data from different angle positions and heights, corresponding to joints of the lower limbs of the human body (ankle, knee, and hip). We use the dataset with a threshold-based fall detection algorithm. The result from the Receiver Operating Characteristic curve shows a good behavior with a mean Area Under the Curve of 0.77 and allow to compute a best threshold value with False Positive Rate of 14.8% and True Positive rate of 89.1%. The optimal threshold value may vary depending on the specific population, activity patterns, and environmental conditions, which may require further customization and validation in real-world settings. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.

2024

Formally Verifying Kyber Episode V: Machine-Checked IND-CCA Security and Correctness of ML-KEM in EasyCrypt

Autores
Almeida, JB; Olmos, SA; Barbosa, M; Barthe, G; Dupressoir, F; Grégoire, B; Laporte, V; Lechenet, JC; Low, C; Oliveira, T; Pacheco, H; Quaresma, M; Schwabe, P; Strub, PY;

Publicação
ADVANCES IN CRYPTOLOGY - CRYPTO 2024, PT II

Abstract
We present a formally verified proof of the correctness and IND-CCA security of ML-KEM, the Kyber-based Key Encapsulation Mechanism (KEM) undergoing standardization by NIST. The proof is machine-checked in EasyCrypt and it includes: 1) A formalization of the correctness (decryption failure probability) and IND-CPA security of the Kyber base public-key encryption scheme, following Bos et al. at Euro S&P 2018; 2) A formalization of the relevant variant of the Fujisaki-Okamoto transform in the Random Oracle Model (ROM), which follows closely (but not exactly) Hofheinz, Hovelmanns and Kiltz at TCC 2017; 3) A proof that the IND-CCA security of the ML-KEM specification and its correctness as a KEM follows from the previous results; 4) Two formally verified implementations of ML-KEM written in Jasmin that are provably constant-time, functionally equivalent to the ML-KEM specification and, for this reason, inherit the provable security guarantees established in the previous points. The top-level theorems give self-contained concrete bounds for the correctness and security of ML-KEM down to (a variant of) Module-LWE. We discuss how they are built modularly by leveraging various EasyCrypt features.

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