CPES

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This service focuses its activities in areas such as regulation and electricity markets, integration of dispersed independent producers, technical and economic management of distribution systems, use of information technologies in regional energy planning, uncertainty and risk management.

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    3D Virtual Labs for Internet Applications
    ( 2011) Fernando Maciel Barbosa ; M. M. Travassos Valdez ; Carlos Machado Ferreira
    This article covers a rather innovative and powerful technology that enables the creation of a 3D interactive laboratory for WEB applications based on open standard VRML format for 3D multimedia and the subsequent distribution of this virtual laboratory on the Internet. The project develops an environment, called 'interactive technology of a 3D Internet Laboratory' to create various types of 3D laboratory experiments as well as their application via the Internet. The application produced is the creation of a 3D virtual laboratory for measurements and instrumentation. The description of the laboratory, fonts and data are also provided. The various steps for creating a 3D virtual laboratory are presented. Lastly, the application of the 'interactive technology laboratory 3D' is displayed and can be considered as a step forward in the development of innovative technologies for distance learning.
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    3D Virtual Reality Experiments To Promote Electrical Engineering Education
    ( 2015) Travassos Valdez,MT ; Machado Ferreira,CM ; Martins,MJM ; Fernando Maciel Barbosa
    3D Virtual Labs are the support of learning, a tool of education in the future. Learning in a 3D environment allows greater interaction with contents in a unique way as students perceive it as being really there. Simulations are being designed, a combination of real-world environment with the information supplied by devices, where measurements can be replicated and data analyzed. This study presents a virtual scenario of a Measurements and Instrumentation laboratory. Electrical Engineering courses aim to train students to succeed in meeting the challenges within competitive and ever-changing professional contexts. In order to prepare undergraduate students for ongoing success, the courses must provide effective training in the application and development of practices, typically implemented in large projects and organizations. Developing high quality engineering course units is definitely a challenging task. Courses can be provided remotely, but careful planning is required to design quality course units because problems may occur in meeting quality targets. The developments in information and communication technologies (ICT), including multimedia and internet-based education platforms, facilitate the creation of reliable solutions to these challenges. Studies show that a smart application of multimedia technologies and web-based education platforms can provide great results towards better quality of engineering courses. Many challenges on how to suitably approach the educational process have already been put forward. Higher Education institutions use multiple approaches to teaching and learning, combining a range of methods, including e-learning, videoconferencing, face-to-face teaching and hard-copy resources in course delivery. The authors present a software model for engineering, which is based mainly on the Wirefusion (R) software, and a virtualreality platform called VEMA. The project intends to improve the quality of teaching and learning in higher education through effective application of information technologies and the sciences of learning. 3D virtual learning environments arise as solutions to the extent that, in addition to offering features associated with communication and information sharing, they promote flexible learning spaces and moments. At the level of higher education, and in accordance with the paradigm of Bologna, virtual environments acquire special importance to allow learning beyond the classroom time and space.
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    Active / reactive bid based dispatch models to be used in electricity markets
    ( 2007) Mário Hélder Gomes ; João Tomé Saraiva
    This paper describes two new active/reactive dispatch models to be used by System Operators in order to assign reactive power and to validate the economic schedules prepared by Market Operators together with the injections related with Bilateral Contracts. When talking about electricity markets one usually refers to active power markets paying less attention to ancillary services, namely to reactive power/voltage control. This usually leads to a chronological sequence of activities that may lead to inefficiencies because active and reactive powers are coupled given the capability diagram of synchronous generators, the ac power flow equations and the branch thermal limits. In this paper, we propose new models to remarry active and reactive allocation procedures based on a market approach as a way to ensure operation transparency. The resulting optimization problems are solved by a Sequential Linear Programming, SLP, approach that allows one to compute active and reactive nodal marginal prices at its final iteration. The paper includes a case study based on the IEEE 24 Bus Test System to illustrate the application of the developed models and demonstrate their interest in the scope of restructured power systems.
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    Active / Reactive Dispatch in Competitive Environment
    ( 2005) João Tomé Saraiva ; Mário Rui Gomes
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    ACTIVE / REACTIVE DISPATCH IN MARKET ENVIRONMENT AND NODAL ACTIVE / REACTIVE PRICE DETERMINATION
    ( 2006) João Tomé Saraiva ; M. H. Gomes
    This paper describes a mathematical formulation for the active/reactive dispatch in electricity markets, addressing a number of technical and economic difficulties present in market models in force in several countries. Traditional market approaches are implemented considering a sequence of activities namely in terms of active power dispatch (via the pool centralized market and bilateral contracts) and ancillary services. However, these two problems are coupled in the sense that dispatching reactive power is not independent from active power scheduling of generators and so a particular reactive power output required by the ISO may be unfeasible in view of the active power dispatch. The proposed model admits that it is known the purely economic pool dispatch together with bilateral contracts and then it aims at dispatching reactive resources considering voltage and branch limit constraints and constraints reflecting the alternator capability curve. The search on the solution spa
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    An Active / Reactive Power Market Dispatch Model Including Soft Constraints
    ( 2006) João Tomé Saraiva ; M. H . Gomes
    This paper describes an active / reactive dispatch model based on bids transmitted by market agents to the Market Operator. The Market Operator economic schedule is then conveyed to the System Operator in order to evaluate its technical feasibility. If it is unfeasible, the System Operator runs a secondary market based on adjustment bids aiming at regaining feasibility while changing as little as possible the initial economic schedule. This secondary market is modeled as a non-linear optimization problem including the AC power flow equations, branch flow and nodal voltage limits as well as constraints related with the capability curve of synchronous generators. This problem is converted into a Symmetric Fuzzy Decision formulation admitting that branch flow and nodal voltage limit constraints have a soft nature. The resulting problem is solved using a Sequential Linear Programming, SLP, approach. The paper includes a case study based on the 24 bus IEEE Test System to illustrat
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    An Active / Reactive Power Market Dispatch Model Including Soft Constraints
    ( 2006) João Tomé Saraiva ; Mário Hélder Gomes
    This paper describes an active / reactive dispatch model based on bids transmitted by market agents to the Market Operator. The Market Operator economic schedule is then conveyed to the System Operator in order to evaluate its technical feasibility. If it is unfeasible, the System Operator runs a secondary market based on adjustment bids aiming at regaining feasibility while changing as little as possible the initial economic schedule. This secondary market is modeled as a non-linear optimization problem including the AC power flow equations, branch flow and nodal voltage limits as well as constraints related with the capability curve of synchronous generators. This problem is converted into a Symmetric Fuzzy Decision formulation admitting that branch flow and nodal voltage limit constraints have a soft nature. The resulting problem is solved using a Sequential Linear Programming, SLP, approach. The paper includes a case study based on the 24 bus IEEE Test System to illustrate its appl
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    Active Distribution Grid Management based on Robust AC Optimal Power Flow
    ( 2018) Ricardo Jorge Bessa ; Tiago André Soares ; Pinson,P ; Morais,H ; 4882 ; 6611
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    Active Management of Electric Vehicles Acting as Distributed Storage
    ( 2016) Filipe Joel Soares ; Almeida,PMR ; Galus,M ; Pedro Pereira Barbeiro ; João Peças Lopes
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    An active reactive bid-based market model using fuzzy sets
    ( 2008) Mário Hélder Gomes ; João Tomé Saraiva
    The restructuring of power systems has often originated the organization of power system operation planning in a set of chronological sequence of activities that are reasonably decoupled. This means that the Market Operator purely economic schedule together with bilateral contracts is conveyed to the System Operator to be validated from a technical point of view. The System Operator also has to schedule reactive power but some of its reactive power requirements may be unfeasible given the previous active power schedules and the alternator capability diagram. Apart from this aspect, active and reactive powers are coupled in determining the eventual violation of branch thermal limits and reactive power has a well-known local nature. While recognizing the coupling between active and reactive powers, the models presented in this paper admit that the Market Operator schedule may have to be altered either because there are branch limit or nodal voltage violations or because the System Operator requires a reactive output that can not be provided due to the previous active schedule. The changes on the initial schedule are determined by solving an optimization problem that uses adjustment generator or demand bids. Apart from that, we adopted a symmetric fuzzy programming approach recognizing that some constraints have a soft nature, namely the ones related with voltage and branch flow limits. To solve the resulting non-linear problem we used Sequential Linear Programmin
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    Active/reactive Market Model Based on Adjustment Bids and Integrating Capacitor Banks and Transformer Taps
    ( 2008) Mário Hélder Gomes ; João Tomé Saraiva
    This paper describes a mathematical model and the developed solution algorithm to solve an integrated active / reactive dispatch while retaining competitive aspects. The main drive for this research was the recognition that the introduction of competitive mechanisms lead to a certain extent to a decoupling between active and reactive power scheduling. Aiming at remarrying them, the developed approach includes an initial bid based uniform price active power auction run by the Market Operator, followed by a technical validity analysis run by the System Operator. If necessary, the System Operator uses adjustment bids to recover the technical feasibility of the dispatch. These bids are presented both by the demand and by generators meaning that demand can play an important role in increasing the liquidity of this specific market. This approach also includes capacitor banks and transformer taps leading to a combinatorial problem solved using Simulated Annealing. Finally, the paper includes results from a case study based on the IEEE 24 Bus Test System to illustrate the interest of this type of approaches.
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    Adaptive Protection Scheme for a Distribution System Considering Grid-Connected and Islanded Modes of Operation
    ( 2016) Ates,Y ; Boynuegri,AR ; Uzunoglu,M ; Nadar,A ; Yumurtaci,R ; Erdinc,O ; Paterakis,NG ; João Catalão
    The renewable energy-based distributed generation (DG) implementation in power systems has been an active research area during the last few decades due to several environmental, economic and political factors. Although the integration of DG offers many advantages, several concerns, including protection schemes in systems with the possibility of bi-directional power flow, are raised. Thus, new protection schemes are strongly required in power systems with a significant presence of DG. In this study, an adaptive protection strategy for a distribution system with DG integration is proposed. The proposed strategy considers both grid-connected and islanded operating modes, while the adaptive operation of the protection is dynamically realized considering the availability of DG power production (related to faults or meteorological conditions) in each time step. Besides, the modular structure and fast response of the proposed strategy is validated via simulations conducted on the IEEE 13-node test system.
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    Addressing th Impact of Demand and Generation Cost Uncertainties in the Operation of Power Systems
    ( 2012) João Tomé Saraiva ; Bruno André Gomes
    This paper describes a set of mathematical formulations designed to include uncertainties modeled by fuzzy numbers in DC OPF studies. These approaches enhance and generalize an initial formulation and solution algorithm described in several papers co-authored by the second author. The approaches described in this paper adopt multiparametric optimization techniques in order to translate to the results the uncertainties affecting loads, for one side, the generation costs, for another, and also both of them in a simultaneous way. These approaches can be very useful nowadays given the uncertainties and volatility affecting data required to run several studies. They can also be the basis for the computation of nodal short time marginal prices reflecting these uncertainties. This paper also includes results obtained from a Case Study based on the IEEE 24 bus test system.
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    Addressing the Impact of Demand and Generation Cost Uncertainties in the Operation of Power Systems
    ( 2012) João Tomé Saraiva ; Bruno André Gomes
    This paper describes a set of mathematical formulations designed to include uncertainties modeled by fuzzy numbers in DC OPF studies. These approaches enhance and generalize an initial formulation and solution algorithm described in several papers co-authored by the second author. The approaches described in this paper adopt multiparametric optimization techniques in order to translate to the results the uncertainties affecting loads, for one side, the generation costs, for another, and also both of them in a simultaneous way. These approaches can be very useful nowadays given the uncertainties and volatility affecting data required to run several studies. They can also be the basis for the computation of nodal short time marginal prices reflecting these uncertainties. This paper also includes results obtained from a Case Study based on the IEEE 24 bus test system.
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    Adequacy and Security Evaluation of Distribution Systems with Distributed Generation
    ( 2012) Diego Issicaba ; João Peças Lopes ; Mauro Rosa
    This paper presents an adequacy and security evaluation of electric power distribution systems with distributed generation. For this accomplishment, bulk power system adequacy and security evaluation concepts are adapted to distribution system applications. The evaluation is supported by a combined discrete-continuous simulation model which emulates the distribution system operation. This model generates a sequence of operation states which are evaluated from a steady-state perspective using AC power flow computations. Frequency and voltage stability are also assessed using dynamic simulation in order to verify the feasibility of islanded operation. Simulation results are presented for the RBTS-BUS2-F1 as well as an actual feeder from the South of Brazil. The results emphasize the need to consider adequacy and security aspects in the distribution system assessments, mainly due to the ongoing integration of distributed energy resources.
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    Adequacy of the long-term operational reserve of a system with wind power and electric vehicles under severe scenarios
    ( 2014) Bremermann,LE ; Da Rosa,MA ; Manuel Matos ; João Peças Lopes ; Leonel Magalhães Carvalho ; Costa,IC
    Combining conventional and unconventional generations with hard forecasting properties and consumption variability has made the task of fitting large amounts of wind generation into unit commitment procedures very challenging. In this context, massive integration of electric vehicles in the electric systems, is expected. This paper aims at evaluating the adequacy of a generating system taking into account the electric vehicles and high wind power integration level in its energy mix. This study was conducted on the European project MERGE framework, and the results have shown that the generating system evaluated is reliable. Nevertheless, the simulations carried out for scenarios with adverse weather conditions (dry years) have revealed specific circumstances that might jeopardize the system adequacy. © 2014 IEEE.
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    Adequacy of the long-term operational reserve of a system with wind power and electric vehicles under severe scenarios
    ( 2014) Bremermann,LE ; da Rosa,MA ; Manuel Matos ; João Peças Lopes ; Leonel Magalhães Carvalho ; Costa,IC
    Combining conventional and unconventional generations with hard forecasting properties and consumption variability has made the task of fitting large amounts of wind generation into unit commitment procedures very challenging. In this context, massive integration of electric vehicles in the electric systems, is expected. This paper aims at evaluating the adequacy of a generating system taking into account the electric vehicles and high wind power integration level in its energy mix. This study was conducted on the European project MERGE framework, and the results have shown that the generating system evaluated is reliable. Nevertheless, the simulations carried out for scenarios with adverse weather conditions (dry years) have revealed specific circumstances that might jeopardize the system adequacy.
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    Adjustable Pitch of Variable Speed Wind Turbine Generation Using a Neural Network Controller
    ( 2006) José Nuno Fidalgo ; António F. Silva F. Silva ; Fernando A. Aristides
    Pitch control has so far been the dominating method for power control in modern variable speed wind turbines. This paper proposes an improved control technique for pitching the blades of a variable speed wind turbine, by application of Artificial Neural Networks (ANN). The control objective is divided into below rated operation and above rated operation. Below rated power, the aim of control is to extract maximum energy from the wind. Above rated power, the control design problem is to limit and smooth the output electrical power. A model has been constructed and validated by experimental data obtained from Vestas V-47 660 kW wind turbine.
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    ADMS4LV – advanced distribution management system for active management of LV grids
    ( 2017) Campos,F ; Marques,L ; Silva,N ; Melo,F ; Seca,L ; Gouveia,C ; André Guimarães Madureira ; Jorge Correia Pereira
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    Advanced Control and Management Functionalities for Multi-MicroGrids
    ( 2011) George Korres ; Nuno José Gil ; João Peças Lopes ; Nikos Hatziargyriou ; André Guimarães Madureira ; Jorge Correia Pereira
    This paper addresses the extension of the Microgrid concept, following a massive integration of these active cells in power distribution networks, by adopting a coordinated management strategy together with Distributed Generation units directly connected to the Medium Voltage distribution network. In order achieve this, a technical and commercial management scheme must be developed for coordinated control of a distribution system with Multi-Microgrids, which should take into account the specific technical capabilities and characteristics of each type of generating source. In particular, tools for coordinated voltage support and frequency control, as well as for state estimation have been developed for this type of networks. Concerning voltage support, a new methodology exploiting an optimization tool based on a meta-heuristic approach was developed. For state estimation, two approaches were considered: Multi-Microgrid State Estimation and Fuzzy State Estimation. Regarding frequency control, the hierarchical structure of the Multi-Microgrid is exploited to deal with the transition to islanded operation and load following in islanded operation. All these tools have proved to be efficient in managing the Multi-Microgrid system in normal interconnected mode and, in case of the frequency control, in islanded operation.