CPES - Indexed Articles in Journals

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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 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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    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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    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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    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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    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.
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    Advanced Control Solutions for Operating Isolated Power Systems: Examining the Portuguese islands
    ( 2015) Helena Vasconcelos ; Carlos Moreira ; André Guimarães Madureira ; João Peças Lopes ; Vladimiro Miranda
    The operation of remote and isolated or islanded power systems is often very challenging because of their small system inertia. Moreover, economic and environmental pressure has led to an increasing renewable power penetration, particularly in wind generation and solar photovoltaics (PV). Simultaneously, significant technological progress has been made in terms of control capability of grid assets [generators, controllable loads such as electric vehicles (EVs), and energy storage systems], mostly exploiting the capabilities of power ?electronics. In this context, several advanced control solutions can be implemented, supporting and improving the robustness of the operation in terms of fast frequency and voltage control responses. In this article, the Portuguese islands are taken as a case study. Within the Madeira archipelago (Porto Santo and Madeira islands), two approaches were envisioned. For Porto Santo Island, the main goal is the sizing of a flywheel energy storage system (FESS) to avoid frequency stability problems. For Madeira Island, the objective relies on the exploitation of hydro resources through the quantification of the technical benefits resulting from variable speed hydro pumping stations that are able to provide primary frequency regulation services in the pump operation mode. In addition, this article also addresses the benefits of introducing EVs in Flores Island in the Azores Archipelago. Finally, to support the development of innovative technological solutions for this type of power system, a laboratory setup based on scaled test systems was also set up and is described. A set of applications was specifically developed for such autonomous power systems. The laboratorial infrastructure allowed the testing of ?solutions and prototypes for hardware and software modules related to those applications. © 2013 IEEE.
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    An advanced platform for power system security assessment accounting for forecast uncertainties
    ( 2019) Ciapessoni,E ; Cirio,D ; Pitto,A ; Omont,N ; Leonel Magalhães Carvalho ; Vasconcelos,MH ; 3348 ; 4971
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    Advanced voltage control for smart microgrids using distributed energy resources
    ( 2017) Olival,PC ; André Guimarães Madureira ; Manuel Matos
    Large scale integration of distributed generation (DG), particularly based on variable renewable energy sources (RES), in low voltage (LV) distribution networks brings significant challenges to operation. This paper presents a new methodology for mitigating voltage problems in LV networks, in a future scenario with high integration of distributed energy resources (DER), taking advantage of these resources based on a smart grid type architecture. These resources include dispersed energy storage systems, controllable loads of residential clients under demand side management (DSM) actions and microgeneration units. The algorithm developed was tested in a real Portuguese LV network and showed good performance in controlling voltage profiles while being able to integrate all energy from renewable sources and minimizing the energy not supplied.
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    Aggregation of Distributed Energy Resources Under the Concept of Multienergy Players in Local Energy Systems
    ( 2017) Yazdani Damavandi,M ; Nilufar Neyestani ; Chicco,G ; Shafie Khah,M ; João Catalão
    In recent years, in addition to the traditional aspects concerning efficiency and profitability, the energy sector is facing new challenges given by environmental issues, security of supply, and the increasing role of the local demand. Therefore, the researchers have developed new decision-making frameworks enabling higher local integration of distributed energy resources (DER). In this context, new energy players appeared in the retail markets, increasing the level of competition on the demand side. In this paper, a multienergy player (MEP) is defined, which behaves as a DER aggregator between the wholesale energy market and a number of local energy systems (LES). The MEP and the LES have to find a long-term equilibrium in the multienergy retail market, in which they are interrelated through the price signals. To achieve this goal, in this paper the decision-making conflict between the market players is represented through a bilevel model, in which the decision variables of the MEP at the upper level are parameters for the decision-making problem at the lower level (for the individual LES). The problem is transformed into a mathematical program with equilibrium constraints by implementing duality theory, which is solved with the CPLEX 12 solver. The numerical results show the different MEP behavior in various conditions that impact on the total flexibility of the energy system.
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    Allocation of Reactive Power Support, Active Loss Balancing and Demand Interruption Ancillary Services in MicroGrids
    ( 2010) Mário Hélder Gomes ; João Tomé Saraiva
    MicroGrids represent a new paradigm for the operation of distribution systems and there are several advantages as well as challenges regarding their development. One of the advantages is related with the participation of MicroGrid agents in electricity markets and in the provision of ancillary services. This paper describes two optimization models to allocate three ancillary services among MicroGrid agents – reactive power/voltage control, active loss balancing and demand interruption. These models assume that MicroGrid agents participate in the day ahead market sending their bids to the MicroGrid Central Controller, MGCC, that acts as an interface with the Market Operator. Once the Market Operator returns the economic dispatch of the Microgrid agents, the MGCC checks its technical feasibility (namely voltage magnitude and branch flow limits) and activates an adjustment market to change the initial schedule and to allocate these three ancillary services. One of the models has crisp nature considering that voltage and branch flow limits are rigid while the second one admits that voltage and branch flow limits are modeled in a soft way using Fuzzy Set concepts. Finally, the paper illustrates the application of these models with a case study using a 55 node MV/LV network.
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    Analysis of Phase Interrogated SPR Fiber Optic Sensors With Bimetallic Layers
    ( 2014) Hamed Moayyed ; Leite,IT ; Luís Carlos Coelho ; José Luís Santos ; Diana Viegas
    An effective analytical model combining geometrical optics with the transfer-matrix theory for stratified optical media is applied to investigate the sensing properties of tapered optical fiber surface plasmon resonance (SPR) sensors incorporating Ag-Au bimetallic layers, particularly in the context of phase interrogation. The performance of the sensing structures is studied as a function of the tapering parameters and thickness of the metallic layers. It is shown that the Ag-Au bimetallic combination is capable of improving the resolution and tuning working region of SPR fiber-optic sensors and that by tapering the sensing structures enhanced sensitivity can be achieved when phase interrogation is considered.
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    Ancillary Services Market Framework for Voltage Control in Distribution Networks with Microgrids
    ( 2012) João Peças Lopes ; André Guimarães Madureira
    In this paper, a proposal for an ancillary services (AS) market framework addressing voltage control in multi-microgrid systems is presented. This var market proposal for MV distribution systems can be adopted to involve Distributed Generation (DG) units and microgrids in AS provision. In the approach that was developed each player is given the opportunity to submit its bid to the var market and the market settlement is performed using an Optimal Power Flow (OPF) formulation in order to minimize the price of reactive power purchased by the Distribution System Operator (DSO). This market is based on var capacity use and runs daily after the scheduling of the generation units for a period of operation of one day.
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    ANN-based scenario generation methodology for stochastic variables of electric power systems
    ( 2016) Vagropoulos,SI ; Kardakos,EG ; Simoglou,CK ; Bakirtzis,AG ; João Catalão
    In this paper a novel scenario generation methodology based on artificial neural networks (ANNs) is proposed. The methodology is flexible and able to generate scenarios for various stochastic variables that are used as input parameters in the stochastic short-term scheduling models. Appropriate techniques for modeling the cross-correlation of the involved stochastic processes and scenario reduction techniques are also incorporated into the proposed approach. The applicability of the methodology is investigated through the creation of electric load, photovoltaic (PV) and wind production scenarios and the performance of the proposed ANN-based methodology is compared to time series-based scenario generation models. Test results on the real-world insular power system of Crete and mainland Greece present the effectiveness of the proposed ANN-based scenario generation methodology.
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    Application of Monte Carlo simulation to generating system well-being analysis considering renewable sources
    ( 2007) Vladimiro Miranda ; Manuel João Aguiar ; Manuel Matos ; João Peças Lopes ; Armando Leite da Silva ; Luiz Antônio Manso ; Warlley S. Sales ; Leonidas Resende
    This paper presents an application of Monte Carlo chronological simulation to evaluate the reserve requirements of generating systems, considering renewable energy sources. The idea is to investigate the behavior of reliability indices, including those from the well-being analysis, when the major portion of the energy sources is renewable. Renewable in this work comprises hydroelectric, mini-hydroelectric, and wind power sources. Case studies on a configuration of the Portuguese Generating System are presented and discussed. Copyright#2006 JohnWiley & Sons, Ltd.
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    An approach to implement data fusion techniques in wireless sensor networks using genetic machine learning algorithms
    ( 2014) Pinto,AR ; Montez,C ; Araujo,G ; Francisco Vasques ; Paulo Portugal
    Wireless Sensor Networks (WSNs) can be used to monitor hazardous and inaccessible areas. In these situations, the power supply (e.g. battery) of each node cannot be easily replaced. One solution to deal with the limited capacity of current power supplies is to deploy a large number of sensor nodes, since the lifetime and dependability of the network will increase through cooperation among nodes. Applications on WSN may also have other concerns, such as meeting temporal deadlines on message transmissions and maximizing the quality of information. Data fusion is a well-known technique that can be useful for the enhancement of data quality and for the maximization of WSN lifetime. In this paper, we propose an approach that allows the implementation of parallel data fusion techniques in IEEE 802.15.4 networks. One of the main advantages of the proposed approach is that it enables a trade-off between different user-defined metrics through the use of a genetic machine learning algorithm. Simulations and field experiments performed in different communication scenarios highlight significant improvements when compared with, for instance, the Gur Game approach or the implementation of conventional periodic communication techniques over IEEE 802.15.4 networks.
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    Artificial immune algorithm applied to distribution system reconfiguration with variable demand
    ( 2016) Souza,SSF ; Romero,R ; Jorge Correia Pereira ; João Tomé Saraiva
    This paper presents a new methodology to solve the reconfiguration problem of electrical distribution systems (EDSs) with variable demand, using the artificial immune algorithm Copt-aiNet (Artificial Immune Network for Combinatorial Optimization). This algorithm is an optimization technique inspired by immune network theory (aiNet). The reconfiguration problem with variable demand is a complex problem of a combinatorial nature. The goal is to identify the best radial topology for an EDS in order to minimize the cost of energy losses in a given operation period. A specialized sweep load flow for radial systems was used to evaluate the feasibility of the topology with respect to the operational constraints of the EDS and to calculate the active power losses for each demand level. The algorithm was implemented in C++ and was evaluated using test systems with 33, 84, and 136 nodes, as well as a real system with 417 nodes. The obtained results were compared with those in the literature in order to validate and prove the efficiency of the proposed algorithm.
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    Assessment of Demand-Response-Driven Load Pattern Elasticity Using a Combined Approach for Smart Households
    ( 2016) Paterakis,NG ; Tascikaraoglu,A ; Erdinc,O ; Bakirtzis,AG ; João Catalão
    The recent interest in the smart grid vision and the technological advancement in the communication and control infrastructure enable several smart applications at different levels of the power grid structure, while specific importance is given to the demand side. As a result, changes in load patterns due to demand response (DR) activities at end-user premises, such as smart households, constitute a vital point to take into account both in system planning and operation phases. In this study, the impact of price-based DR strategies on smart household load pattern variations is assessed. The household load datasets are acquired using model of a smart household performing optimal appliance scheduling considering an hourly varying price tariff scheme. Then, an approach based on artificial neural networks (ANN) and wavelet transform (WT) is employed for the forecasting of the response of residential loads to different price signals. From the literature perspective, the contribution of this study is the consideration of the DR effect on load pattern forecasting, being a useful tool for market participants such as aggregators in pool-based market structures, or for load serving entities to investigate potential change requirements in existing DR strategies, and effectively plan new ones.