ISEL - Eng. Electrotécn. - Comunicações
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- Protection against direct atmospheric discharges and overvoltages in photovoltaic installationsPublication . Coelho, Gonçalo; Barata, Filipe; Elvas, Luís; Viveiros, CarlaThe increasing global energy demand has led to the expansion of photovoltaic (PV) power plants, particularly in response to climate goals like the European Union's "Fit for 55" initiative to reduce CO2 emissions by 55% by 2030. However, as PV installations grow, their vulnerability to atmospheric discharges, such as lightning, also increases. This study investigates the design and dimensioning of lightning protection systems for PV plants, focusing on two methods: traditional protection per IEC 62305 standards and ionizing devices based on NP 4426 standards. Both methods were analyzed for technical feasibility and cost-effectiveness. A case study of the PV installations at the Lisbon Engineering School (ISEL) was conducted, and a risk analysis determined that Level III protection was required. The study demonstrated that both methods provide effective protection, but ionizing devices offer a more cost-efficient solution, with lower material and labor costs. Consequently, the study showed that ionizing method is around 35% affordable than traditional rods for protecting PV plants in urban environment against atmospheric discharges.
- 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.
- ESS design and management considering solar PV to fed off-grid EV chargerPublication . Santos, Diogo; Fonte, Pedro M; Pereira, Rita; Barata, Filipe; Almeida, Paulo; Cordeiro, Armando; Luís, Ricardo; Fernao Pires, VitorThe increase of electric vehicles creates several challenges to the electric grid, mainly in those with weak power or off-grid. DC microgrids are becoming more and more important in the context of renewable energy sources, where solar PV systems are dominant. In this paper is proposed the design of a DC system to charge electric vehicles using PV generation and a battery storage system. A single DC-DC converter is used to operate the solar PV array with maximum power point tracking method and controls power flow from PV to storage battery and to the EV, operating as DC EV charger. The operation under various loading conditions is discussed. The performance of the proposed solution was simulated using MATLAB/Simulink software.
- A SRM for a PV powered water pumping system based on a multilevel converter and DC/DC dual output converterPublication . Foito, Daniel; Fernao Pires, Vitor; Cordeiro, Armando; Amaral, Tito; Chaves, Miguel; Pires, Armando; Martins, JoaoThis paper focuses on a proposal for a system based on a photovoltaic (PV) supply for a powered water pumping. The system consists in a switched reluctance machine (SRM) controlled by a multilevel converter and fed by PV panels associated to a DC/DC converter. The multilevel power converter proposed to control the SRM was designed to minimize the switches and to support the balance of the two input capacitors. The DC/DC converter consists in a hybrid solution that merges a Buck-Boost converter with a Sepic converter. They use a topology solution in which the input current presents a reduced ripple and only requires one switch. This DC/DC converter is also characterized by a dual output to adapt to the multilevel converter. The control system and a maximum power point tracking (MPPT) algorithm are also presented. The operation of this system will be verified by tests that are done by computer simulations.
- Combining power electronic converters and automation to simulate solar PV systemsPublication . Cordeiro, Armando; Chaves, Miguel; Gamboa, Paulo; Barata, Filipe; Fonte, Pedro M; Lopes, Hélio; Fernao Pires, Vitor; Foito, Daniel; Amaral, Tito; Martins, JoaoThis paper presents a solar photovoltaic panel simulator system with the ability to perform automatic tests in different condition according to manufacture parameters. This simulator is based on three buck-boost DC-DC converters controlled by a microcontroller and supported by a Programmable Logic Controller which is responsible for the automatic tests. This solution will allow to achieve fast response, like suddenly changes in the irradiation, temperature, or load. To control the power converter, it will be used a fast and robust sliding mode controller. Therefore, with the proposed system is possible to perform the I-V curve simulation of a solar PV panel, evaluate different MPPT algorithms considering different meteorological and load variation. The main advantage of this work is the possibility to evaluate and test several MPPT algorithms and understand the operation and typical operation of solar PV panels in different conditions. Several simulations and experimental results from a laboratory prototype are presented to confirm the theoretical operation.
- Power quality and modeling analysis of a university campus electrical distribution systemPublication . Ferrolho, César; Barata, Filipe; Gamboa, PauloFor a few years now, electrical power quality has been a topic of interest and discussion, mainly due to issues regarding costs, continuity of service and electrical installation energy efficiency. The lack in electrical power quality can reveal itself in different ways, in reactive power costs, in frequent tripping of protections, in overheating and overloads of equipment and cables, in the significant shortening of capacitor lifespans, and, on power grid resonance events. This paper makes an electrical power quality analysis on Instituto Superior de Engenharia de Lisboa (ISEL) school campus, more precisely, two transformer substations and several building electrical distribution boards that make up the campus’ electrical power grid. The acquired data enabled the graphical display of several electrical parameters, and their subsequent quantitative and qualitative analysis, regarding legislation and standards, namely, NP EN 50160; IEC 61000-2-3 and IEEE Std 1159-2019. In the paper, a Matlab/Simulink model of ISEL campus’ electrical power grid was developed, so that, when anomalies are identified, it will be possible to analyze and verify, through simulation, the effect that different solutions produce to mitigate them.
- Wireless home automation system for multifunctional devices incorporating Internet of Things (IoT)Publication . Pedro, Bruno; Barata, Filipe; Canacsinh, HirenHome automation systems have been increasing in quantity and quality, throughout the world. The scientific community has been spending its resources to improve these systems, regarding their capabilities, accessibility and price. In this article, a low cost, home automation system, in the form of an experimental prototype is presented, focused in wireless communication and IoT (Internet of Things) structures. The result of the work developed was a capable prototype, adaptable to conventional electrical installations, with smart management capabilities regarding actuators of electric loads and sensor information utilization.
- Economic and energy feasibility using photovoltaic solar energy sources as a response to the energy consumption of the municipality of BarcarenaPublication . Simões, Fábio; Viveiros, Carla; Barata, FilipeThis article provides an economic and energy feasibility study for the implementation of renewable photovoltaic energy sources, in the municipality of Barcarena, in order to sustain electric energy consumption, taking into account technological advances, the expected population increase and the energy potential of the study area. The consumption of electricity of the municipality under study is analysed, as well as their distribution among the various types of existing electricity production. The economic and energy influence of this implementation is analysed through different case studies, in order to meet the targets defined by the Oeiras Council with regard to the Sustainable Energy for Oeiras Action Plan (PAESO).