2011
Autores
Da Rocha, MC; Saraiva, JT;
Publicação
17th Power Systems Computation Conference, PSCC 2011
Abstract
This paper presents a discrete approach, based on an improved integer version of the evolutionary particle swarm optimization (EPSO) algorithm, to solve the dynamic transmission expansion planning (TEP) problem. TEP corresponds to a mixed integer optimization problem that typically aims at identifying a schedule for transmission additions along an extended planning horizon considering operation and investment costs as well as a reliability index to measure the ability the system has to convey electricity from generation to consumers. After detailing the mathematical formulation of the TEP problem, this paper describes the enhanced EPSO algorithm and details its application to the TEP problem. The paper also includes a Case Study based on the IEEE 24 bus / 38 branch system to illustrate the application of the developed procedure.
2011
Autores
Saraiva, JT; Heitor, H; Correia, N; Araujo, R;
Publicação
2011 IEEE PES Trondheim PowerTech: The Power of Technology for a Sustainable Society, POWERTECH 2011
Abstract
This paper analyses and discusses the current situation in Portugal and in Spain regarding the procurement and the supply of the ancillary services considered in the Codes for the Operation of these two power systems. This is relevant because Portugal and Spain share a common day ahead and bilateral contract electricity market since 2007. However, several technical activities as the procurement and the provision of Ancillary Services are not yet entirely harmonized and fully integrated and continue to be provided within the control area of each country. Accordingly, this paper discusses three possible approaches that the two TSO's can adopt to further enlarge this integration. Then, tertiary reserve is taken as an example to illustrate the advantages that can be obtained if it is used a common list of bids from the two countries. The Case Study analyses four situations including the present mechanisms used to procure tertiary reserve, as well as the use of a common bid list admitting different values for the capacity of the interconnection lines between the two countries. Based on these results, the paper provides a discussion on the mentioned three integration models addressing their advantages and practical difficulties. © 2011 IEEE.
2011
Autores
Andre Gomes, B; Saraiva, JT;
Publicação
2011 8th International Conference on the European Energy Market, EEM 11
Abstract
This paper reviews the concepts and the solution algorithm of the Fuzzy DC OPF problem admitting generation costs and load values modeled by fuzzy numbers and details the integration of this problem in the Monte Carlo simulation model. In this sense, the paper describes an hybrid approach in which generation cost and demand uncertainties are represented by fuzzy numbers and the life cycle of the system components is modeled by probabilistic approaches. On this topic, the paper addresses the sampling procedure, the analysis of sampled states, the convergence testing and the computation of the expected values of the system Power Not Supplied and system risk indices. Finally, the paper includes results based on the IEEE 24 bus/38 branch test system to illustrate the proposed approach. © 2011 IEEE.
2011
Autores
Pereira, AJC; Saraiva, JT;
Publicação
17th Power Systems Computation Conference, PSCC 2011
Abstract
This paper describes a long-term simulation model to help generation companies building expansion plans. Different from the past, the generation activity is now provided under competition, and investments are affected by uncertainties and by the decisions of other players. This paper describes the use of System Dynamics to model the evolution of the demand and of the electricity price along the planning horizon. These evolutions will then be used by individual agents to prepare their own expansion plans. These plans will globally have to comply with general constraints, typically present in Grid Codes, as for instance, a maximum value for an adequacy index as LOLE. This model and the corresponding solution algorithm will be illustrated using a Case Study to illustrate the use of the developed approach to build the expansion plans and to conduct sensitivity studies.
2011
Autores
Saraiva, JT; Heitor, H; Correia, N; Araujo, R;
Publicação
2011 8th International Conference on the European Energy Market, EEM 11
Abstract
This paper addresses the provision of ancillary services in Portugal and Spain in the scope of the Common Iberian Electricity market. The paper reviews the definitions and the international practice regarding ancillary services with emphasis on primary, secondary and tertiary reserves and describes the procedures adopted by the Portuguese and Spanish TSO's to procure and allocate reserve levels. On the other hand, the paper discusses the models that can be used to enlarge the integration of the reserve markets, namely regarding tertiary reserve. Using data from 2009, the paper presents the results of the simulations that were performed for several situations including an ideal unlimited interconnection capacity, the existing interconnection capacity and an interconnection capacity increased by 300 MW. The results obtained indicate that the adoption of a common tertiary reserve list would ultimately be beneficial for the consumers since the cost of tertiary reserve would be reduced. However, a larger integration and cooperation between the two TSO's would be clearly required. © 2011 IEEE.
2011
Autores
Tavares, A; Dias, SRS; Carvalho, CMB; Faustino, MAF; Tome, JPC; Neves, MGPMS; Tome, AC; Cavaleiro, JAS; Cunha, A; Gomes, NCM; Alves, E; Almeida, A;
Publicação
PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES
Abstract
Photodynamic therapy is a very promising approach to inactivate pathogenic microorganisms. The photodamage of cells involves reactive oxygen species (ROS) which are generated in situ by two main mechanisms (type I and/or type II). The mechanism responsible for the photoinactivation (PI) of a bioluminescent recombinant Escherichia coli, induced by three different cationic porphyrins, was identified in this work using a rapid method based on the monitoring of the metabolic activity of this bacterium. The inhibitory effect of the photodynamic process in the presence of a singlet oxygen quencher (sodium azide) or free radical scavengers (D-mannitol and L-cysteine) was evaluated by exposing bacterial suspensions with 0.5 mu M Tri-Py+-Me-PF, 5.0 mu M Tetra-Py+-Me or 5.0 mu M Tri-SPy+-Me-PF to white light. Strong bacterial protection was observed with sodium azide (100 mM) for the three cationic porphyrins. However, in the presence of Tri-Py+-Me-PF and Tetra-Py+-Me and the free radical scavengers (L-cysteine and D-mannitol) the reduction on the bacterial bioluminescence was significantly higher and similar to that obtained in their absence (5.4-6.0 log reduction). In the case of Tri-SPy+-Me-PF two distinct behaviours were observed when L-cysteine and D-mannitol were used as free radical scavengers: while the presence of L-cysteine (100 mM) lead to a bacterial protection similar to the one observed with sodium azide, in the presence of D-mannitol only a small protection was detected. The high inhibition of the PS activity by L-cysteine is not due to its radical scavenger ability but due to the singlet oxygen quenching by the sulfanyl group (-SH). In fact, the photodecomposition of 1,3-diphenylisobenzofuran in the presence of Tri-SPy+-Me-PF is completely suppressed when L-cysteine is present. The results obtained in this study suggest that singlet oxygen (type II mechanism) plays a very important role over free radicals (type I mechanism) on the PI process of the bioluminescent E. coli by Tri-Py+-Me-PF, Tetra-Py+-Me and Tri-SPy+-Me-PF. Although the use of scavengers is an adequate and simple approach to evaluate the relative importance of the two pathways, it is important to choose scavengers which do not interfere in both PI mechanisms. Sodium azide and D-mannitol seem to be good oxygen and free radical quenchers, respectively, to study the PI mechanisms by porphyrinic photosensitizers.
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