Accountability and revenue metering in smart micro-grids

Smart micro-grids offer a new challenging domain for power theories and metering techniques, because they include a variety of intermittent power sources which positively impact on power flow and distribution losses, but may cause voltage asymmetry and frequency variation. Due to the limited power capability of smart micro-grids, the voltage distortion can also get worse (in case of supplying non-linear loads), affecting measurement accuracy and possibly causing tripping of protections. In such a context, a reconsideration of power theories is required, since they form the basis for supply and load characterization. A revision of revenue metering techniques is also needed, to ensure a correct penalization of the loads for their responsibility in generating reactive power, voltage unbalance and distortion. This paper shows that the Conservative Power Theory (CPT) provides a suitable background to cope with smart grids characterization and metering needs. Experimental results validate the proposed approach. © 2010 IEEE.

Distributed generation modelling for unbalanced three-phase power flow calculations in smart grids

Distributed Generators (DG) are generally modeled as PQ or PV buses in power flow studies. But in order to integrate DG units into the distribution systems and control the reactive power injection it is necessary to know the operation mode and the type of connection to the system. This paper presents a single-phase and a three-phase mathematical model to integrate DG in power flow calculations in distribution systems, especially suited for Smart Grid calculations. If the DG is in PV mode, each step of the power flow algorithm calculates the reactive power injection from the DG to the system to keep the voltage in the bus in a predefined level, if the DG is in PQ mode, the power injection is considered as a negative load. The method is tested on two well known test system, presenting single-phase results on 85 bus system, and three-phase results in the IEEE 34 bus test system. © 2011 IEEE.

Comparative analysis for reactive energy measurement methodologies, under non-sinusoidal conditions in three-phase four-wire circuits

This paper presents some methodologies for reactive energy measurement, considering three modern power theories that are suitable for three-phase four-wire non-sinusoidal and unbalanced circuits. The theories were applied in some profiles collected in electrical distribution systems which have real characteristics for voltages and currents measured by commercial reactive energy meters. The experimental results are presented in order to analyze the accuracy of the methodologies, considering the standard IEEE 1459-2010 as a reference. Finally, for additional comparisons, the theories will be confronted with the modern Yokogawa WT3000 energy meter and three samples of a commercial energy meter through an experimental setup. © 2011 IEEE.

Comparação entre modelos do dispositivo FACTS STATCOM para o estudo da estabilidade a pequenas perturbações

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Metodologia de projeto cooperativo para condicionadores de qualidade de energia

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Valoração de serviços ancilares de geradores distribuídos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Otimização multiobjetivo da compensação de potência reativa em redes de distribuição considerando restrições de distorção harmônica

A localização de bancos de capacitores nas redes de distribuição de energia elétrica, corretamente dimensionados, busca compensar eventuais excessos de circulação de potência reativa pelas linhas, o que implica a redução de custos operacionais pela redução das perdas de energia e um aumento da capacidade de transmissão de potência ativa assegurando os níveis estabelecidos de tensão e fator de potência simultaneamente. A proliferação das cargas não lineares provocou uma mudança nos cenários de estudo dos sistemas elétricos de potência devido aos efeitos nocivos que os harmônicos gerados por elas ocasionam sobre a qualidade da energia elétrica. Considerando este novo cenário, esta tese tem como objetivo geral desenvolver uma ferramenta computacional utilizando técnicas de inteligência computacional apoiada em algoritmos genéticos (AG), para a otimização multiobjetivo da compensação da potência reativa em redes elétricas de distribuição capaz de localizar e dimensionar de forma ótima as unidades de compensação necessárias para obter os melhores benefícios econômicos e a manutenção dos índices de qualidade da energia estabelecidos pelas normas brasileiras. Como Inovação Tecnológica do trabalho a ferramenta computacional desenvolvida permite otimizar a compensação da potência reativa para melhorar do fator de potência em redes de distribuição contaminadas com harmônicos que, diferentemente de métodos anteriores, não só emprega bancos de capacitores, mas também filtros de harmônicos com esse objetivo. Utiliza-se o algoritmo NSGA-II, que determina as soluções ótimas de Pareto para o problema e permite ao especialista determinar as soluções mais efetivas. A proposta para a solução do problema apresenta várias inovações podendo-se destacar que a solução obtida permite determinar a compensação de potência reativa com capacitores em sistemas com certa penetração harmônica, atendendo a normas de qualidade de energia pertinentes, com relação aos níveis de distorção harmônica tolerados.

Application of carbon composite adsorbents prepared from coffee waste and clay for the removal of reactive dyes from aqueous solutions

A novel carbon composite was prepared from a mixture of coffee waste and clay with inorganic:organic ratio of 1.3 (CC-1.3). The mixture was pyrolysed at 700 °C. Considering the application of this adsorbent for removal of anionic dyes, the CC-1.3 was treated with a 6 mol L^-1 HCl for 24 h to obtain ACC-1.3. Fourier transform infrared (FTIR), N₂ adsorption/desorption curves, scanning electron microscope (SEM) and powder X-ray diffractometry (XRD) were used for characterisation of CC-1.3 and ACC-1.3 carbon adsorbents. The adsorbents were effectively utilised for removal of reactive blue 19 (RB-19) and reactive violet 5 (RV-5) textile dyes from aqueous solutions. The maximum amounts of RB-19 dye adsorbed at 25 °C are 63.59 (CC-1.3) and 110.6 mg g^-1 (ACC-1.3), and 54.34 (CC-1.3) and 94.32 mg g^-1 (ACC-1.3) for RV-5 dye. Four simulated dye-house effluents were used to test the application of the adsorbents for treatment of effluents.

Multi-task control strategy for grid-tied inverters based on conservative power theory

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Novel expert system for defining power quality compensators

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Instantaneous complex power applied to three-phase machines

The theory presented in this paper was primarily developed to give a physical interpretation for the instantaneous power flow on a three-phase induction machine, without a neutral conductor, on any operational state and may be extended to any three-phase load. It is a vectorial interpretation of the instantaneous reactive power theory presented by Akagi et al. Which, believe the authors, isn't enough developed and its physical meaning not yet completely understood. This vectorial interpretation is based on the instantaneous complex power concept defined by Torrens for single-phase, ac, steady-state circuits, and leads to a better understanding of the power phenomenon, particularly of the distortion power. This concept has been extended by the authors to three-phase systems, through the utilization of the instantaneous space vectors. The results of measurements of instantaneous complex power on a self-excited induction generator's terminals, during an over-load application transient, are presented for illustration. The compensation of reactive power proposed by Akagi is discussed and a new horizon for the theory application is opened.

Proposta de metodologia para o gerenciamento automático de sistemas fotovoltaicos de geração distribuída

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Funções penalidade para o tratamento das variáveis discretas do problema de fluxo de potência ótimo reativo

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Power laws, Discontinuities and Regional City Size Distributions

Urban systems are manifestations of human adaptation to the natural environment. City size distributions are the expression of hierarchical processes acting upon urban systems. In this paper, we test the entire city size distributions for the southeastern and southwestern United States (1990), as well as the size classes in these regions for power law behavior. We interpret the differences in the size of the regional city size distributions as the manifestation of variable growth dynamics dependent upon city size. Size classics in the city size distributions are snapshots of stable states within urban systems in flux.

Dynamic Range of Vertebrate Retina Ganglion Cells: Importance of Active Dendrites and Coupling by Electrical Synapses

The vertebrate retina has a very high dynamic range. This is due to the concerted action of its diverse cell types. Ganglion cells, which are the output cells of the retina, have to preserve this high dynamic range to convey it to higher brain areas. Experimental evidence shows that the firing response of ganglion cells is strongly correlated with their total dendritic area and only weakly correlated with their dendritic branching complexity. On the other hand, theoretical studies with simple neuron models claim that active and large dendritic trees enhance the dynamic range of single neurons. Theoretical models also claim that electrical coupling between ganglion cells via gap junctions enhances their collective dynamic range. In this work we use morphologically reconstructed multi-compartmental ganglion cell models to perform two studies. In the first study we investigate the relationship between single ganglion cell dynamic range and number of dendritic branches/total dendritic area for both active and passive dendrites. Our results support the claim that large and active dendrites enhance the dynamic range of a single ganglion cell and show that total dendritic area has stronger correlation with dynamic range than with number of dendritic branches. In the second study we investigate the dynamic range of a square array of ganglion cells with passive or active dendritic trees coupled with each other via dendrodendritic gap junctions. Our results suggest that electrical coupling between active dendritic trees enhances the dynamic range of the ganglion cell array in comparison with both the uncoupled case and the coupled case with cells with passive dendrites. The results from our detailed computational modeling studies suggest that the key properties of the ganglion cells that endow them with a large dynamic range are large and active dendritic trees and electrical coupling via gap junctions.