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Publications

Publications by CPES

2018

Protection Systems and Earthing Schemes for Microgrids: Main Aspects and Fault Analysis

Authors
Bandeiras, F; Gomes, M; Coelho, P; Fernandes, J; Moreira, C;

Publication
INTERNATIONAL JOURNAL OF EMERGING ELECTRIC POWER SYSTEMS

Abstract
The content of this paper aims to assist in the development and implementation of microgrids by addressing the challenges and possible solutions for their protection systems. Therefore, an overview of some protection methods available in the literature that can be implemented to ensure a safe and reliable microgrid operation is presented, including the most common protection devices and earthing schemes that can be adopted in low voltage distribution systems. In addition, this paper also presents a brief fault analysis of internal faults at three different locations in an industrial microgrid with centralized and decentralized deployment of energy sources, as well as a short-circuit analysis of symmetric and asymmetric faults at these faulty locations. An approximate method based on the calculation of the equivalent impedance seen from the fault location is used to determine the fault currents. This study is made to observe how microgrids with different configurations perform in the event of internal faults. It is demonstrated in this work that setting a specific protection strategy to allow the microgrid to operate effectively during both operation modes can be problematic and expensive in most situations. With this in mind, additional effort is necessary to engineer and implement new protection approaches that can overcome the limitations of protection systems in future microgrids.

2018

Active Distribution Grid Management Based on Robust AC Optimal Power Flow

Authors
Soares, T; Bessa, RJ; Pinson, P; Morais, H;

Publication
IEEE TRANSACTIONS ON SMART GRID

Abstract
Further integration of distributed renewable energy sources in distribution systems requires a paradigm change in grid management by the distribution system operators (DSOs). DSOs are currently moving to an operational planning approach based on activating flexibility from distributed energy resources in day/hour-ahead stages. This paper follows the DSO trends by proposing a methodology for active grid management by which robust optimization is applied to accommodate spatial-temporal uncertainty. The proposed method entails the use of a multi-period AC-OPF, ensuring a reliable solution for the DSO. Wind and PV uncertainty is modeled based on spatial-temporal trajectories, while a convex hull technique to define uncertainty sets for the model is used. A case study based on real generation data allows illustration and discussion of the properties of the model. An important conclusion is that the method allows the DSO to increase system reliability in the real-time operation. However, the computational effort grows with increases in system robustness.

2018

Data Economy for Prosumers in a Smart Grid Ecosystem

Authors
Bessa, RJ; Rua, D; Abreu, C; Machado, P; Andrade, JR; Pinto, R; Goncalves, C; Reis, M;

Publication
E-ENERGY'18: PROCEEDINGS OF THE 9TH ACM INTERNATIONAL CONFERENCE ON FUTURE ENERGY SYSTEMS

Abstract
Smart grids technologies are enablers of new business models for domestic consumers with local flexibility (generation, loads, storage) and where access to data is a key requirement in the value stream. However, legislation on personal data privacy and protection imposes the need to develop local models for flexibility modeling and forecasting and exchange models instead of personal data. This paper describes the functional architecture of an home energy management system (HEMS) and its optimization functions. A set of data-driven models, embedded in the HEMS, are discussed for improving renewable energy forecasting skill and modeling multi-period flexibility of distributed energy resources.

2018

Data Economy for Prosumers in a Smart Grid Ecosystem

Authors
Bessa, RJ; Rua, D; Abreu, C; Machado, P; Andrade, JR; Pinto, R; Gonçalves, C; Reis, M;

Publication
Proceedings of the Ninth International Conference on Future Energy Systems, e-Energy 2018, Karlsruhe, Germany, June 12-15, 2018

Abstract

2018

Influence of Crowbar and Chopper Protection on DFIG during Low Voltage Ride Through

Authors
Monteiro Pereira, RMM; Pereira, AJC; Ferreira, CM; Maciel Barbosa, FPM;

Publication
ENERGIES

Abstract
The energy sector is evolving rapidly, namely due to the increasing importance of renewable energy sources. The connection of large amounts of wind power generation poses new challenges for the dynamic voltage stability analysis of an electric power system, which has to be studied. In this paper, the traditional Doubly-Fed Induction Generator model is employed. Based on this model, a crowbar and chopper circuit is set up to protect the turbine during the short-circuit period. The EUROSTAG software package was used for the simulation studies of the system, and numerical results were obtained. Conclusions are drawn that provide a better understanding of the influence of crowbar and chopper protection on Doubly-Fed Induction Generators (DFIG), during low voltage ride through, in a system with wind power generation.

2018

Application of virtual reality tools in the teaching of concepts in projects of fast loading stations

Authors
Travassos Valdez, MT; Machado Ferreira, CM; Maciel Barbosa, FPM;

Publication
2018 28TH EAEEIE ANNUAL CONFERENCE (EAEEIE)

Abstract
The classroom will always present great challenges to the teachers. It is important to know how to provide learning to a new generation of students and to try to understand how students learn today. Each student arrives at school with a diversity of knowledge resulting from their own life experience, probably divergent from that of their colleagues. On the other hand, the domain of the new Information and Communication Technologies (ICTs) is part of their own experience. The teacher/student relationship is becoming more and digital and, therefore, the limitations of space are more and more reduced. ICTS have greatly altered the way students have access to knowledge, how they share it or how they simply organize the work. Thus, traditional pedagogical strategies and processes must integrate technologies, as a way to apply new work methodologies that value the students' reflection and critical thinking. In return, technology will bring them closer to knowledge, increasing their autonomy and consequent motivation. This work aimed at introducing the topic of sustainable mobility, so that electric vehicles become a growing reality in everyday life. A power generation system was proposed using a grid of photovoltaic panels, which in turn will allow the sustained feeding of a quick charging station. The surplus of electricity produced by the grid of panels can be used to meet the energy needs of a service station. A varied range of software tools were used to address the challenge. This article aims at discussing the use of different software in the educational environment, highlighting the advantages, as well as the difficulties associated with the approach. Several educational software types were used in the final project of a master's degree in ISEC (Instituto Superior de Engenharia de Coimbra). Software tools are an effective way to train students. The use of virtual reality tools in concept teaching of fast charging stations was quite effective in the improvement of students.

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