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- ItemLimitação das correntes de curto-circuito para minimizar o impacto da elevada integração de geração distribuída na proteção de alimentadores em média tensão(Universidade Federal do Espírito Santo, 2024-09-13) Rocha Junior, Edmilson Bermudes; Simonetti, Domingos Sávio Lyrio ; https://orcid.org/0000-0001-5920-2932; http://lattes.cnpq.br/1107005171102255; Batista, Oureste Elias ; http://orcid.org/0000-0003-4719-4132; http://lattes.cnpq.br/3717606765861586; http://orcid.org/0000-0001-8956-8548; http://lattes.cnpq.br/8631253817692368; Fardin, Jussara Farias; https://orcid.org/0000-0003-4785-556X; http://lattes.cnpq.br/1912113095988528; Santos, Walbermark Marques dos; https://orcid.org/0000-0002-9871-6028; http://lattes.cnpq.br/5558697161842579; Lopes, Felipe Vigolvino; https://orcid.org/0000-0001-6465-8045; http://lattes.cnpq.br/3155646870666658; Araújo, Marcel Ayres de ; https://orcid.org/0000-0002-3403-4650; http://lattes.cnpq.br/0669410110930611With the increasing number of distributed generators connected to distribution systems, which traditionally had centralized generation, networks are now configured to allow bidirectional energy flow. This scenario has significant impacts on short-circuit currents, not only altering their magnitude but also their direction, directly affecting the effectiveness of overcurrent protections. The complexity is compounded by the fact that algorithms used by protection device manufacturers are not publicly disclosed, hindering advancements in the field of protection. This study investigates the behavior of short-circuit currents in a context of high penetration of distributed generation, considering different types of faults at specific locations on a medium-voltage distribution feeder. The technique adopted for short-circuit current detection involves defining a reference current value, reading instantaneous current values in each phase, comparing them with the reference value, and calculating the derivative using the Euler method. This approach was implemented alongside a solid-state current limiter on the IEEE 13 NTF test feeder with varying levels of power injected by distributed generators. Simulation results indicate an average detection time of approximately 250 ms. Regarding current limitation, significant variations in short-circuit current magnitudes were observed. The highest average variations were 85.01% for single-phase faults, 87.60% for two-phase faults, and 94.09% for three-phase faults
- ItemAI-based strategies for handover enhancement in visible light communication systems(Universidade Federal do Espírito Santo, 2025-03-21) Camporez, Higor Araújo Fim; Silva, Jair Adriano Lima; https://orcid.org/; http://lattes.cnpq.br/3099010533644898; Wortche, Heinrich; https://orcid.org/0000-0003-2263-0495; http://lattes.cnpq.br/4357799865954315; Rocha, Helder Roberto de Oliveira; https://orcid.org/0000-0001-6215-664X; http://lattes.cnpq.br/8801325729735529; https://orcid.org/0000-0003-2197-8588; http://lattes.cnpq.br/5910374743077555; Pohl, Alexandre de Almeida Prado; https://orcid.org/0000-0003-1300-4679; http://lattes.cnpq.br/9118815178885363; Zanotelli, Tiago; https://orcid.org/0000-0001-9467-2710; http://lattes.cnpq.br/7490836346926791; Pontes, Maria José; https://orcid.org/0000-0002-9009-2425; http://lattes.cnpq.br/4148956242627659; Ciarelli, Patrick Marques; https://orcid.org/0000-0003-3177-4028; http://lattes.cnpq.br/1267950518719423The Internet of Things (IoT) growth, particularly applications involving wireless devices, has significantly increased the demand for signal bandwidth. However, Radio Frequency (RF) wire less systems presented a limited spectrum to support massive device connections and suscepti bility to electromagnetic interference. These challenges have increased the interest in exploring alternative solutions to face RF issues while maintaining high data rates, low latency, reliability, and cost efficiency. Advancements in Light Emitting Diode (LED) technology have introduced highly energy-efficient lighting capable of high-speed modulation of light intensity. Thus, these characteristics have driven research into Visible Light Communication (VLC), which can uti lize existing lighting infrastructures for data transmission using a broad and unregulated optical spectrum (≈ 400 THz). Additionally, VLC can also provide physical layer security, low power consumption, high transmission speeds, and immunity to RF electromagnetic interference. Spectral efficiency and high data rates are critical for VLC systems, with Orthogonal Fre quency Division Multiplexing (OFDM) emerging as a robust and spectrally efficient modulation technique for indoor applications. However, nonlinearities introduced by multicarrier signals in LED-based systems can degrade performance. To address these issues, techniques such as Constant-Envelope OFDM (CE-OFDM) have been developed to mitigate Peak-to-Average Power Ratio (PAPR), improving power efficiency and reducing distortions, particularly in high power transmission scenarios. Additionally, VLC faces several challenges, including signal blockage by opaque objects, confinement of signals, and limited Access Point (AP) coverage. Addressing these limitations often requires deploying ultra-dense networks to ensure reliable connectivity across large areas. However, such dense deployments can lead to frequent han dovers, increasing infrastructure costs and complexity. This thesis evaluates the application of larger signal amplitudes despite the LED-nonlinearities to enable data transmission over long distances, evaluating the conventional and constant envelope OFDMperformances. Furthermore, it proposes a ModifiedGeneticAlgorithm(MGA) optimization procedure combined with time series Machine Learning (ML) classifiers to min imize handovers in both a digital twin-based simulation system and experimental VLC setups. The proposed handover scheme considers receiver trajectory information to reduce handover frequency while maintaining system performance within the forward error correction limit. Results demonstrate that a 9.51 Mb/s CE-OFDM system with 16-QAM subcarrier map ping in a 5MHz bandwidth outperformed a conventional OFDM system in terms of efficiency. The application of the CE-OFDM scheme in a 6m VLC link reduced the EVM from 17.5%to 10%, an improvement of approximately 43%. Additionally, the CE-OFDM-based VLC system demonstrated satisfactory performance in an 8 m link when using 4-QAM subcarrier mapping. The proposed handover scheme outperforms a power-based approach, achieving han dover reductions of 42.47% in a MISO simulation environment and up to 48.61% in a MIMO environment. In experimental scenarios with three and four transmitters, the scheme achieved reductions of 46.43% and 45.45%, respectively. These results confirm that the integration of MGAwithMLmodelseffectively minimizes handovers and improves overall VLC system per formance
- ItemOptimization approaches for enhanced operation and planning of distribution systems : a multi-objective perspective(Universidade Federal do Espírito Santo, 2025-02-25) Ferraz, Renato Santos Freire; Rueda Medina, Augusto César ; https://orcid.org/0000-0002-4291-3153; http://lattes.cnpq.br/7397584412509839; https://orcid.org/0000-0001-7571-1972; http://lattes.cnpq.br/1832936459743268; Fardin, Jussara Farias; https://orcid.org/0000-0003-4785-556X; http://lattes.cnpq.br/1912113095988528; Batista, Oureste Elias; http://orcid.org/0000-0003-4719-4132; http://lattes.cnpq.br/3717606765861586; Franco Baquero, John Fredy ; https://orcid.org/0000-0002-7191-012X; http://lattes.cnpq.br/8253028254016321; Donadel, Clainer Bravin ; https://orcid.org/0000-0002-3310-2762; http://lattes.cnpq.br/8624415630257203Efficient planning and operation strategies are essential for modern electric power networks to ensure cost-effective electricity delivery while maintaining reliable performance. However, the ongoing transformation of traditional centralized distribution systems, driven by the integration of distributed energy resources (DERs) and the growing adoption of electric vehicles (EVs), has introduced new and complex challenges for distribution system operators (DSOs). To address these issues, this thesis proposes multi-objective optimization approaches aimed at enhancing the planning and operation of distribution networks from the DSO’s perspective. The first approach focuses on the optimized allocation and sizing of DERs while ensuring recloser fuse coordination to preserve the original network protection scheme. The second approach handles the static network reconfiguration problem, incorporating the allocation and sizing of DERs and capacitors. The third approach extends this to dynamic network reconfiguration, considering DERs, capacitors, and electric vehicle charging stations. Finally, the fourth approach explores the dynamic network reconfiguration, capacitors allocation, and on-load tap changer adjustment, while accounting for stochastic customer-owned DERs. The main objectives are to minimize investment and operational costs, improve the system’s performance indicators–such as power losses and voltage deviation–and ensure the proper operation of the distribution system. Stochastic variations in DER generation, load profiles, and EV distribution throughout the day are modeled using the Monte Carlo Method. The multi-objective optimization problems are solved using the Non-dominated Sorting Genetic Algorithm II and the Multi-objective Cuckoo Search, with the final solution selected through the Fuzzy Decision-making Method. The results demonstrate significant improvements in the performance indicators of the distribution system, achieved while meeting all operational constraints
- ItemOtimização multiobjetivo para a alocação e dimensionamento de geradores distribuídos e estações de carregamento lento e rápido considerando programas de resposta à demanda(Universidade Federal do Espírito Santo, 2025-02-06) Ferraz, Rafael Santos Freire; Fardin, Jussara Farias ; https://orcid.org/0000-0003-4785-556X; http://lattes.cnpq.br/1912113095988528; Rueda Medina, Augusto César; https://orcid.org/0000-0002-4291-3153; http://lattes.cnpq.br/7397584412509839; https://orcid.org/0000-0001-8857-011X; http://lattes.cnpq.br/5323068276181437; Donadel, Clainer Bravin ; https://orcid.org/0000-0002-3310-2762; http://lattes.cnpq.br/8624415630257203; Antunes, Helio Marcos Andre ; https://orcid.org/0000-0001-8247-6448; http://lattes.cnpq.br/7601860538588447; Melo Trujillo, Joel David ; https://orcid.org/0000-0001-5046-1890; http://lattes.cnpq.br/4396532007704107; Encarnação, Lucas Frizera ; https://orcid.org/0000-0002-6162-7697; http://lattes.cnpq.br/5578918284508758The growing insertion of Electric Vehicles (EVs) and, consequently, a lack of planning in the installation of Electric Vehicle Charging Stations (EVCSs) can result in negative impacts on the electricity network. Therefore, the optimized allocation and sizing of EVCSs are important for reducing the costs of installing and operating the stations, in addition to the costs incurred by EV users for travel and recharging. Furthermore, the correct determination of slow and fast charging modes, combined with the adoption of demand response programs such as smart charging and Time of Use tariffs, are essential for reducing the aforementioned costs. These measures also contribute to the improvement of the voltage profile and the minimization of power losses in the distribution system. The purpose of this thesis is to conduct the optimized planning of public EVCSs, as well as the optimized allocation and sizing of Distributed Energy Resources (DERs), since DERs can play an important role in reducing the negative effects on the power grid caused by the large increase in EV demand. Therefore, this thesis includes four approaches using the proposed methodology. In the first approach, the methodology was tested in the IEEE 34-node test system, considering only the fast charging mode. In the second approach, only the slow charging mode was analyzed in the 33-node test system integrated with a 25-node traffic system. In the third approach, the planning of charging stations considered the integration of both fast and slow charging modes into the traffic systems interconnected with the distribution systems. Finally, in the fourth approach, in addition to this integration, the charging prices for both modes were treated as decision variables in the problem, also incorporating the perspective of the system operator. Additionally, a novel methodology was introduced for the spatiotemporal distribution of EVs over 24 hours based on closeness centrality from Graph Theory, considering commercial and residential areas in the studied systems. Different multi-objective algorithms were used to solve the presented problem, aiming to validate the methodology. It is important to highlight that the choice of the optimized solution was determined by graphical analysis or the Fuzzy Decision-Making Method. In all approaches, a significant reduction in the negative impacts of EV charging demand on the distribution system was observed, including power losses and voltage deviations. Furthermore, there was a decrease in recharging and travel costs for EV users, as well as a minimization of the costs for the system operator with the installation and operation of EVCSs and DERs
- ItemSilicon photonic integrated circuits as an enabling technology for passive optical network architectures(Universidade Federal do Espírito Santo, 2024-11-27) Marciano, Pablo Rafael Neves; Pontes, Maria José ; https://orcid.org/0000-0002-9009-2425; http://lattes.cnpq.br/4148956242627659; Segatto, Marcelo Eduardo Vieira ; https://orcid.org/0000-0003-4083-992X; http://lattes.cnpq.br/2379169013108798; https://orcid.org/0000-0001-8333-8012; http://lattes.cnpq.br/2070224436956646; Castellani, Carlos Eduardo Schmidt ; https://orcid.org/0000-0003-4154-5683; http://lattes.cnpq.br/1975160943820607; Rocha, Helder Roberto de Oliveira ; https://orcid.org/0000-0001-6215-664X; http://lattes.cnpq.br/8801325729735529; Nunes, Reginaldo Barbosa ; https://orcid.org/0000-0001-8877-1480; http://lattes.cnpq.br/0301147577506989; Conforti, Evandro ; https://orcid.org/0000-0002-4570-3725; http://lattes.cnpq.br/4808617538189330This work explored different PIC solutions, and their applications for optical networks were evaluated. Also, optical network techniques were applied to a new hybrid PON architecture focused on demonstrating the main characteristic that future networks must develop. There, a novel hybrid PON architecture associated with PIC was proposed for future generations of telecommunication systems. For instance, the PIC can implement optically complex functions traditionally implemented in the digital domain, allow future PON to implement an all-optical orthogonal frequency division multiplexing, and recover the data without using digital-signal processing devices. Also, the chromatic dispersion precompensation concept on the optical domain is exploited in this work, as we experimentally demonstrate the optical pre-equalization of OFDM-based optical IMDD systems in 125 km of optical fiber links through a photonic integrated circuit. The experiments with the PIC used OFDM signals with 5 GHz and 10 GHz with optical precompensation and without the traditional one-tap equalizer for simple optical OFDM systems. The results show significant enhancements in system performance and an improvement in power consumption. The capability of reducing latency is assured by reducing signal duration, which is a gold requirement for 5G New-Radio, PONs, and other networks