Metodologia heurística construtiva para alocação de bancos de capacitores em sistemas de distribuição de energia elétrica

This paper presents a heuristic constructive algorithm to solve the discrete capacitor size and allocation problem in distribution systems. Initially the discrete nature of the capacitor allocation problem is mitigated by using a sigmoid function in the [0,1] interval which is incorporated into the optimum power flow (OPF) through modifications in the power flow equations. The proposed algorithm uses the primal-dual interior point technique to solve the OPF problem. Finally, the sensitivity obtained by sigmoid function which is weighted by the reactive loading of the distribution system, determines step by step the location, size and number of capacitors to be installed in the distribution system. The proposed technique is applied in two distribution systems. The results obtained are compared with the ones obtained using the genetic algorithm.Este artigo apresenta um algoritmo heurístico construtivo para a resolução do problema referente à alocação ótima de bancos fixos de capacitores em sistemas de distribuição. Inicialmente a natureza discreta do problema de alocação de capacitores é mitigada através do uso de uma função sigmoidal no intervalo [0,1] que é incorporada ao problema de fluxo de potência ótimo (FPO) através de modificações nas equações de fluxo de potência. O algoritmo proposto utiliza a técnica primal-dual de pontos interiores como ferramenta de solução do FPO. Baseado na sensibilidade fornecida pela função sigmoidal ponderada pelo carregamento da potência reativa do sistema de distribuição, a metodologia heurística proposta determina passo a passo a localização, a capacidade e o número de capacitores a serem instalados no sistema. A técnica proposta é aplicada a dois sistemas de distribuição de energia. Os resultados são comparados com os resultados obitidos através de um algoritmo genético

Determinação da operação de unidades térmicas para o estudo de Unit Commitment através de uma análise de sensibilidade

This paper proposes the utilization of a new sensibility index to organize a priority list for the solution of the Unit Commitment problem. The discrete nature of the operational decisions is mitigated through a continuous function. Thus the new index is derived from the lagrangian multipliers and the non-linear optimization problem is solved using the interior point primal-dual method. The priority list is obtained as a by-product of the lagrangian multipliers associated with the "ON-OFF" decision. The efficiency of the proposed methodology is demonstrated through several tests.Este artigo propõe a utilização de um novo índice de sensibilidade à elaboração de uma lista de prioridade para a resolução do problema de "Unit Commitment". O novo índice é obtido através dos multiplicadores de Lagrange associado às variáveis discretas inerentes ao problema, as quais são mitigadas através de uma função contínua. Desta forma, o problema de otimização não linear é resolvido através da utilização da metodologia primal-dual de pontos interiores e como subproduto têm-se os multiplicadores de Lagrange associados às variáveis de decisão "ON-OFF" para a elaboração de uma lista de prioridade. Os resultados obtidos mostram a eficiência da metodologia proposta

Statement of Second Brazilian Congress of Mechanical Ventilarion : part I

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Impacts of the Tropical Pacific/Indian Oceans on the Seasonal Cycle of the West African Monsoon

The current consensus is that drought has developed in the Sahel during the second half of the twentieth century as a result of remote effects of oceanic anomalies amplified by local land–atmosphere interactions. This paper focuses on the impacts of oceanic anomalies upon West African climate and specifically aims to identify those from SST anomalies in the Pacific/Indian Oceans during spring and summer seasons, when they were significant. Idealized sensitivity experiments are performed with four atmospheric general circulation models (AGCMs). The prescribed SST patterns used in the AGCMs are based on the leading mode of covariability between SST anomalies over the Pacific/Indian Oceans and summer rainfall over West Africa. The results show that such oceanic anomalies in the Pacific/Indian Ocean lead to a northward shift of an anomalous dry belt from the Gulf of Guinea to the Sahel as the season advances. In the Sahel, the magnitude of rainfall anomalies is comparable to that obtained by other authors using SST anomalies confined to the proximity of the Atlantic Ocean. The mechanism connecting the Pacific/Indian SST anomalies with West African rainfall has a strong seasonal cycle. In spring (May and June), anomalous subsidence develops over both the Maritime Continent and the equatorial Atlantic in response to the enhanced equatorial heating. Precipitation increases over continental West Africa in association with stronger zonal convergence of moisture. In addition, precipitation decreases over the Gulf of Guinea. During the monsoon peak (July and August), the SST anomalies move westward over the equatorial Pacific and the two regions where subsidence occurred earlier in the seasons merge over West Africa. The monsoon weakens and rainfall decreases over the Sahel, especially in August.Peer reviewe

Search for heavy resonances decaying to two Higgs bosons in final states containing four b quarks

A search is presented for narrow heavy resonances X decaying into pairs of Higgs bosons (H) in proton-proton collisions collected by the CMS experiment at the LHC at root s = 8 TeV. The data correspond to an integrated luminosity of 19.7 fb(-1). The search considers HH resonances with masses between 1 and 3 TeV, having final states of two b quark pairs. Each Higgs boson is produced with large momentum, and the hadronization products of the pair of b quarks can usually be reconstructed as single large jets. The background from multijet and t (t) over bar events is significantly reduced by applying requirements related to the flavor of the jet, its mass, and its substructure. The signal would be identified as a peak on top of the dijet invariant mass spectrum of the remaining background events. No evidence is observed for such a signal. Upper limits obtained at 95 confidence level for the product of the production cross section and branching fraction sigma(gg -> X) B(X -> HH -> b (b) over barb (b) over bar) range from 10 to 1.5 fb for the mass of X from 1.15 to 2.0 TeV, significantly extending previous searches. For a warped extra dimension theory with amass scale Lambda(R) = 1 TeV, the data exclude radion scalar masses between 1.15 and 1.55 TeV

Measurement of the top quark mass using charged particles in pp collisions at root s=8 TeV

Peer reviewe

Search Space Reduction for the Thermal Unit Commitment Problem through a Relevance Matrix

Given the combinatorial explosion related to the operation decisions in the thermal unit commitment problem, this paper presents a new strategy to reduce the search space and to start the multi-modal optimization process. To achieve such goals, a relevance matrix is obtained to indicate how important each generating unit is at each hour of the operational planning. This matrix is generated through the results of a constructive heuristic based on sensitivity indexes that account for operational and economic characteristics of the generating units and of the system under planning. The proposed method is shown to reduce the complexity of the problem, thus decreasing the combinatorial explosion and, consequently, the computational burden. Its effectiveness is verified by performing optimizations with and without its utilization. The results achieved with the proposed space-reduction approach enable solutions that present good quality. Furthermore, these solutions are retrieved with significantly reduced processing time

Search Space Reduction for the Thermal Unit Commitment Problem through a Relevance Matrix

Given the combinatorial explosion related to the operation decisions in the thermal unit commitment problem, this paper presents a new strategy to reduce the search space and to start the multi-modal optimization process. To achieve such goals, a relevance matrix is obtained to indicate how important each generating unit is at each hour of the operational planning. This matrix is generated through the results of a constructive heuristic based on sensitivity indexes that account for operational and economic characteristics of the generating units and of the system under planning. The proposed method is shown to reduce the complexity of the problem, thus decreasing the combinatorial explosion and, consequently, the computational burden. Its effectiveness is verified by performing optimizations with and without its utilization. The results achieved with the proposed space-reduction approach enable solutions that present good quality. Furthermore, these solutions are retrieved with significantly reduced processing time

Estudo e Otimização do Modelo SMAP: Study and Optimization of the SMAP model

A previsibilidade da vazão disponível para as plantas hidrelétricas alguns dias a frente é de extrema importância para o planejamento e operação do sistema elétrico. É possível obter estas previsões através do uso de modelos hidrológicos que caracterizam a região de estudo. Este trabalho visa aplicar o modelo SMAP a três sub-bacias brasileiras, com o uso de algoritmos de inteligência computacional para a calibração dos parâmetros de chuva. GWO e BA foram os algoritmos utilizados. Os resultados mostraram que o GWO apresentou uma convergência mais rápida, porém os resultados obtidos pelo BA foram melhores

Modified Genetic Algorithm for the Profit-Based Unit Commitment Problem in Competitive Electricity Market

This article proposes a solution to the Profit-Based Unit Commitment (PBUC) problem to maximize the profit of a power generation company that owns thermal units and compressed air energy storage (CAES) systems, considering the Day-Ahead market. The proposed methodology is more realistic as it considers a mixed-integer nonlinear formulation of the PBUC. The problem is solved through two stages, with Stage 1 dedicated to obtaining the operational state of the generating units (On or Off) and the operation mode of the storage system (energy exchange: charging, discharging, idle). Stage 2 determines the dispatch of power from the thermoelectric units and the energy exchange in the storage system. The analysis of the system consisting of 20 thermoelectric units and three storage systems shows the efficiency of the proposed method in making decisions for the power generation company and is therefore promising for real-world applications