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Detalhes

Detalhes

  • Nome

    Rui Esteves Araujo
  • Cargo

    Investigador Sénior
  • Desde

    01 abril 2010
009
Publicações

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 P. Monteiro et al., licensed to EAI. This is an open access article distributed under the terms of the CC BY-NC-SA 4.0. All Rights Reserved.

2024

Switched reluctance motor core loss estimation with a new method based on static finite elements

Autores
Sousa Melo P.; Esteves Araújo R.;

Publicação
Cogent Engineering

Abstract
Core loss estimation in switched reluctance motor is a complex task, due to non-linear phenomena and non-sinusoidal flux density waveforms. Several methods have been developed for estimating it (e.g. empirical, and physical-mathematic models), each one with merits and limitations. This paper proposes a new method for core losses estimation based on Finite Element Method Magnetics software. The main idea is using the machine phase-current harmonics as input for estimating core losses. In addition, a comparative study is carried out, where the proposed approach is faced up to a different one, based on Fourier decomposition of the flux density waveforms in the machine sections. In order to systematically analyze and compare the applied estimation cores loss techniques, a case study of a three-phase 6/4 SRM for different simulation scenarios is introduced. The outcomes of both methods are discussed and compared, where core loss convergence is found for limited speed and load ranges.

2024

Fuzzy Super-Twisting Sliding Mode Controller for Switched Reluctance Wind Power Generator in Low-Voltage DC Microgrid Applications

Autores
Touati, Z; Mahmoud, I; Araújo, RE; Khedher, A;

Publicação
Energies

Abstract
There is limited research focused on achieving optimal torque control performance of Switched Reluctance Generators (SRGs). The majority of existing studies tend to favor voltage or power control strategies. However, a significant drawback of SRGs is their susceptibility to high torque ripple. In power generation systems, torque ripple implicates fluctuations in the generated power of the generator. Moreover, high torque ripple can lead to mechanical vibrations and noise in the powertrain, impacting the overall system performance. In this paper, a Torque Sharing Function (TSF) with Indirect Instantaneous Torque Control (IITC) for SRG applied to Wind Energy Conversion Systems (WECS) is proposed to minimize torque ripple. The proposed method adjusts the shared reference torque function between the phases based on instantaneous torque, rather than the existing TSF methods formulated with a mathematical expression. Additionally, this paper introduces an innovative speed control scheme for SRG drive using a Fuzzy Super-Twisting Sliding Mode Command (FSTSMC) method. Notably robust against parameter uncertainties and payload disturbances, the proposed scheme ensures finite-time convergence even in the presence of external disturbances, while effectively reducing chattering. To assess the effectiveness of the proposed methods, comprehensive comparisons are made with traditional control techniques, including Proportional–Integral (PI), Integral Sliding Mode Control (ISMC), and Super-Twisting Sliding Mode Control (STSMC). The simulation results, obtained using MATLAB®/SIMULINK® under various speeds and mechanical torque conditions, demonstrate the superior performance and robustness of the proposed approaches. This study presents a thorough experimental analysis of a 250 W four-phase 8/6 SRG. The generator was connected to a DC resistive load, and the analysis focuses on assessing its performance and operational characteristics across different rotational speeds. The primary objective is to validate and confirm the efficacy of the SRG under varying conditions. © 2024 by the authors.

2023

Model-Free Finite-Set Predictive Current Control With Optimal Cycle Time for a Switched Reluctance Motor

Autores
Pereira, M; Araujo, RE;

Publicação
IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS

Abstract
Traditional use of predictive control techniques require the knowledge of the systems model to control and the use of constant cycle-time. In the case of a switched reluctance motor its model is highly nonlinear and time-varying with current magnitude and rotor position. The use of look-up tables has been one solution, but requires a complete knowledge of the motor and mismatches from the original model used in the design can happen due temperature variation or changes in operating regimes. To address these issues as well as to increase the tracking performance of current control, a model-free predictive algorithm is developed by updating the next cycle time of the next time step of the predictive control. A new parameter estimation method is proposed that identifies the parameters of the switched reluctance model with low computational burden. Based on knowledge of the parameters at real time, not only the ideal voltage vector is applied at each cycle but the ideal time that each cycle must have is also calculated. As result, the advanced current controller requires almost no knowledge of the motor in use. The performance of the proposed schemes is validated through simulation and by a prototype experimental setup. Experimental data shows a decreasing in prediction error around 78 per cent, when comparing to the predefined model controller.

2023

Two-Outputs Nonlinear Grey Box Model for Lithium-Ion Batteries

Autores
da Silva, CT; Dias, BMD; Araujo, RE; Pellini, EL; Lagana, AAM;

Publicação
ENERGIES

Abstract
Storing energy efficiently is one of the main factors of a more sustainable world. The battey management system in energy storage plays an extremely important role in ensuring these systems' efficiency, safety, and performance. This battery management system is capable of estimating the battery states, which are used to give better efficiency, a long life cycle, and safety. However, these states cannot be measured directly and must be estimated indirectly using battery models. Therefore, accurate battery models are essential for battery management systems implementation. One of these models is the nonlinear grey box model, which is easy to implement in embedded systems and has good accuracy when used with a good parameter identification method. Regarding the parameter identification methods, the nonlinear least square optimization is the most used method. However, to have accurate results, it is necessary to define the system's initial states, which is not an easy task. This paper presents a two-outputs nonlinear grey box battery model. The first output is the battery voltage, and the second output is the battery state of charge. The second output was added to improve the system's initial states identification and consequently improve the identified parameter accuracy. The model was estimated with the best experiment design, which was defined considering a comparison between seven different experiment designs regarding the fit to validation data, the parameter standard deviation, and the output variance. This paper also presents a method for defining a weight between the outputs, considering a greater weight in the output with greater model confidence. With this approach, it was possible to reach a value 1000 times smaller in the parameter standard deviation with a non-biased and little model prediction error when compared to the commonly used one-output nonlinear grey box model.

Teses
supervisionadas

2022

An intelligent approach to fault tolerance in cyber physical systems

Autor
Luis Fernando Piardi

Instituição
UNL-FCTNOVA

2022

Impact of demand response and electrical energy storage on multi-energy systems management

Autor
Morteza Vahid Ghavidel

Instituição
UP-FEUP

2022

Transporte Robotizado de Bagagens em Aeroportos

Autor
PEDRO MATIAS LOPES LEMOS

Instituição
IPP-ISEP

2021

DESENVOLVIMENTO DE UM MODELO DE SERVIÇOS DE PRODUÇÃO URBANA ASSENTE NA IMPRESSÃO ADITIVA EM PROJETO ABERTO (OPEN DESIGN)

Autor
PAULO DUARTE VALENTE DE OLIVEIRA GOULÃO

Instituição
IPP-ISEP

2021

Self-Learning Artificial Intelligence for Laser Induced Breakdown Spectroscopy: Data Analysis and System Control

Autor
Alberto Sousa Lima Mesquita dos Santos

Instituição
UP-FEUP