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Publications

Publications by CPES

2021

Would Self-healing be economically justifiable on LV networks?

Authors
Santos, MGM; Carreira, JG; Gouveia, C; Madureira, G; Penedos, T; Prata, R; Lourenço, F;

Publication
IET Conference Proceedings

Abstract
Self-healing (SH) functions have been studied through pilots on E-REDES Medium Voltage (MV) network with positive results. The natural next step would be to apply the SH concept to Low Voltage (LV) networks. However, LV and MV networks have distinct characteristics (criticality, capillarity, complexity, energy distributed by km of network, technology, etc.). The economic criteria that justify SH on MV network are not applicable to LV networks. This article presents and discusses several challenges related to implement SH to LV networks and other aspects to be considered. The SH concept is discussed when applied to LV network. Also, the advantages that operational management can achieve with this concept available on daily operations. Other big challenge is the technology evolution that must occur on sensors and, most of all, actuators, to accommodate automatisms and to be remotely monitored and controlled. Also, a telecommunication solution needs to be established to support the real-time interaction between all the components. Last, but not least, the economic aspect. How and when can an extra cost be justifiable on a network that didn't felt the necessity to be automated for so many years. Should we start to consider it now? Two use-cases are proposed. © 2021 The Institution of Engineering and Technology.

2021

Advances in the computational analysis of SARS-COV2 genome

Authors
Machado, JAT; Rocha Neves, JM; Azevedo, F; Andrade, JP;

Publication
NONLINEAR DYNAMICS

Abstract
Given a data-set of Ribonucleic acid (RNA) sequences we can infer the phylogenetics of the samples and tackle the information for scientific purposes. Based on current data and knowledge, the SARS-CoV-2 seemingly mutates much more slowly than the influenza virus that causes seasonal flu. However, very recent evolution poses some doubts about such conjecture and shadows the out-coming light of people vaccination. This paper adopts mathematical and computational tools for handling the challenge of analyzing the data-set of different clades of the severe acute respiratory syndrome virus-2 (SARS-CoV-2). On one hand, based on the mathematical paraphernalia of tools, the concept of distance associated with the Kolmogorov complexity and Shannon information theories, as well as with the Hamming scheme, are considered. On the other, advanced data processing computational techniques, such as, data compression, clustering and visualization, are borrowed for tackling the problem. The results of the synergistic approach reveal the complex time dynamics of the evolutionary process and may help to clarify future directions of the SARS-CoV-2 evolution.

2021

Wind Farm Cable Connection Layout Optimization with Several Substations

Authors
Cerveira, A; Pires, EJS; Baptista, J;

Publication
ENERGIES

Abstract
Green energy has become a media issue due to climate changes, and consequently, the population has become more aware of pollution. Wind farms are an essential energy production alternative to fossil energy. The incentive to produce wind energy was a government policy some decades ago to decrease carbon emissions. In recent decades, wind farms were formed by a substation and a couple of turbines. Nowadays, wind farms are designed with hundreds of turbines requiring more than one substation. This paper formulates an integer linear programming model to design wind farms' cable layout with several turbines. The proposed model obtains the optimal solution considering different cable types, infrastructure costs, and energy losses. An additional constraint was considered to limit the number of cables that cross a walkway, i.e., the number of connections between a set of wind turbines and the remaining wind farm. Furthermore, considering a discrete set of possible turbine locations, the model allows identifying those that should be present in the optimal solution, thereby addressing the optimal location of the substation(s) in the wind farm. The paper illustrates solutions and the associated costs of two wind farms, with up to 102 turbines and three substations in the optimal solution, selected among sixteen possible places. The optimal solutions are obtained in a short time.

2021

Evaluation of pv microgeneration systems and tariffs management on the energy efficiency of service buildings

Authors
Baptista, J; Sequeira, G; Solteiro Pires, EJ;

Publication
Renewable Energy and Power Quality Journal

Abstract
The buildings' energy consumption increasing requires solutions to improve their energy efficiency, thus reducing the electricity bill's associated costs. This paper aims to study the load profiles of a service building and its optimization to reduce the costs related to electricity consumption. The electrical load profiles are analyzed, and the electrical equipment and its consumption are characterized. Moreover, to increase energy efficiency and reduce energy costs, a renewable energy system based on photovoltaic panels is sized and integrated into the building. The analysis of the building's consumption profiles allowed the PV system's dimensioning to eliminate power peaks, enabling a reduction in the contracted power. The results demonstrate the effectiveness of the proposed solution, resulting in a reduction of the electricity bill.

2021

Optimization of Wind Turbines Placement in Offshore Wind Farms: Wake Effects Concerns

Authors
Baptista J.; Lima F.; Cerveira A.;

Publication
Communications in Computer and Information Science

Abstract
In the coming years, many countries are going to bet on the exploitation of offshore wind energy. This is the case of southern European countries, where there is great wind potential for offshore exploitation. Although the conditions for energy production are more advantageous, all the costs involved are substantially higher when compared to onshore. It is, therefore, crucial to maximize system efficiency. In this paper, an optimization model based on a Mixed-Integer Linear Programming model is proposed to find the best wind turbines location in offshore wind farms taking into account the wake effect. A case study, concerning the design of an offshore wind farm, were carried out and several performance indicators were calculated and compared. The results show that the placement of the wind turbines diagonally presents better results for all performance indicators and corresponds to a lower percentage of energy production losses.

2021

Harmonic emissions of a bidirectional electric vehicle charging station - a research methodology based on tests at a reconstructed smart grid

Authors
Grasel, B; Baptista, J; Tragner, M; Leonhartsberger, K; Igel, S;

Publication
2021 21ST IEEE INTERNATIONAL CONFERENCE ON ENVIRONMENT AND ELECTRICAL ENGINEERING AND 2021 5TH IEEE INDUSTRIAL AND COMMERCIAL POWER SYSTEMS EUROPE (EEEIC/I&CPS EUROPE)

Abstract
Bidirectional electric vehicle charging stations (EVSE) offer new business models to users and can provide ancillary services to the electrical grid. During charging operation EMC standards and during discharging grid codes are applicable. In this study the harmonic emissions including the total harmonic distortion (THD) and total distortion demand factor (TDD) together with the grid impedance up to 2 kHz of a 10 kW bidirectional charging station are analyzed. While harmonic emission measurements of EVSE at laboratory conditions gives results for idealized conditions and field tests strongly depend on local grid conditions, the real-life operation of an EVSE at a well-known reconstructed grid gives valuable information about the harmonic behavior and impact to the grid impedance. The results show that the bidirectional EVSE can be a main pollutant of harmonic emissions at low power set-points, harmonic phase angle can change from inductive to capacitive behavior and the first resonance frequency of the grid impedance is moved to lower frequencies.

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