Browsing by Issue Date, starting with "2024-12-31"
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- Efficient feature selection for intrusion detection systems with priority queue-based GRASPPublication . Quincozes, Vagner E.; Quincozes, Silvio E.; Albuquerque, Célio; Passos, Diego; Massé, DanielThe Greedy Randomized Adaptive Search Proce dure for Feature Selection (GRASP-FS) is a recently-proposed metaheuristic that optimizes the feature selection process for Intrusion Detection Systems (IDS) by combining exploration and refinement techniques for more assertive intrusion detection. However, GRASP-FS may be time and resource-consuming for large datasets. In this work, we propose GRASPQ-FS, an extended version of GRASP-FS using Priority Queues to reduce resource consumption and processing time. As an additional contribution, we provide a comprehensive analysis of the most suitable parameters for our RASPQ-FS. Our results reveal that GRASPQ-FS can speed up feature selection up to 90% over GRASP-FS, without compromising F1-Score. Also, we observed that a priority queue with 50 solutions saved 50% in execution time while increasing the F1-Score by 4.5%.
- A single-switch DC-DC converter with a high voltage gain capability and reduced voltage stress of the switch for renewable energy applicationsPublication . Fernao Pires, Vitor; Cordeiro, Armando; Foito, Daniel; Monteiro, Joaquim; Silva, J. F.The growing trend toward high-efficiency, high gain converters that minimize component count, has spurred the development of many new step-up topologies. In this context introduces a new single-switch, non-isolated DC-DC step-up converter topology specifically designed for renewable energy applications. Key advantages of this topology include a high boost factor, continuous input current, reduced voltage stress on the switch, and a suitable number of elements relative to the achieved boost factor. These features address many of the critical design objectives. The steady-state analysis of the proposed converter is presented and discussed. Simulation and experimental results are presented to verify the theory and performance of the converter.
- Isolated quasi-switched boost integrated T-type DC-DC converter for DC microgridPublication . Ferreira, Daniel; Cordeiro, Armando; Rocha, Luís; Romero-Cadaval, Enrique; Roncero Clemente, Carlos; Silva, J. Fernando; Foito, Daniel; Martins, João F.; Fernao Pires, VitorOver the last few years, there has been a high demand for new or improved isolated DC-DC to fulfill requirements of applications related with RES. In this context, this paper introduces a new isolated DC-DC converter, for use in renewable energy applications. The topology proposed contains an Active quasi-switched Boost Three-Level T-type DC-DC converter with continuous input current at the converter input side, connected to a high-frequency step-up isolation transformer, and a voltage doubler rectifier (VDR) on the output side. The steady-state analysis of the proposed converter is presented and discussed. Simulation results are presented to verify the theory and performance of the converter.
- Transformerless ultra-high gain buck-boost DC-DC converter with single-switch of reduced voltage stressPublication . Cordeiro, Armando; Gamboa, Paulo; Luís, Ricardo; Fonte, Pedro M; Monteiro, Joaquim; Martins, João F.; Silva, J. Fernando; Foito, Daniel; Fernao Pires, VitorThis paper introduces a new DC-DC power converter topology capable of both step-up and step-down voltage conversion, with an exceptionally high voltage gain ratio.. Besides the high extension of the voltage gain range, the converter is also characterized by the use of a single switch. Moreover, the stress imposed on the switch's voltage is minimized, enabling the utilization of low-voltage, low RDS-ON MOSFETs. Consequently, this modification leads to reduced costs and losses associated with switch conduction and turn ON. Another aspect concerning the proposed converter is that the input current exhibits a continuous behavior, which can be significant for various applications. The paper provides insights into the operational performance, steady state behavior, and mathematical underpinnings of the proposed dc-dc converter. Comparative evaluation of the static voltage gain of the proposed converter and other topologies with comparable characteristics will also be shown. Verification of the presented converter's key features are conducted through both simulation and experimental assessments using a 440-W laboratory prototype. Through these analyses, the efficacy and viability of the modified coupled-inductor SEPIC converter with enhanced voltage gain capability are confirmed.
- Diagnosing Power Transistor Faults in Multilevel T-Type Based Nine Switch Inverter Using Center of Mass IndexesPublication . Monteiro, Joaquim; Amaral, Tito; Silva, J. Fernando; Pinto, Sonia; Fernao Pires, VitorNine-switch voltage source inverters (NSVSI) are DC-AC converters that utilize a reduced number of switches, making them advantageous for dual or six-phase motors. To enhance the quality of the output voltage and provide fault tolerant capability, NSVSI topologies, like the T-Type-based NSVSI, have been modified to operate as multilevel converters. However, to ensure fault-tolerant capability, a fault diagnosis algorithm for power transistors must be developed. Therefore, this paper proposes a novel fault detection and diagnosis algorithm to identify faulty transistors in a multilevel T-Type-based NSVSI. This method is based on the development of specific indices derived from the center of mass of the output currents. The proposed technique offers a fast and reliable solution, demonstrating robustness under various load conditions. The effectiveness of this method will be validated through a series of simulation tests.