Harmonic propagation analysis in electric energy distribution systems

An important alteration of the equivalent loads profile has been observed in the electrical energy distribution systems, for the last years. Such fact is due to the significant increment of the electronic processors of electric energy that, in general, behave as nonlinear loads, generating harmonic distortions in the currents and voltages along the electric network. The effects of these nonlinear loads, even if they are concentrated in specific sections of the network, are present along the branch circuits, affecting the behavior of the entire electric network. For the evaluation of this phenomenon it is necessary the analysis of the harmonic currents flow and the understanding of the causes and effects of the consequent voltage harmonic distortions. The usual tools for calculation the harmonic flow consider one-line equivalent networks, balanced and symmetrical systems. Therefore, they are not tools appropriate for analysis of the operation and the influence/interaction of mitigation elements. In this context, this work proposes the development of a computational tool for the analysis of the three-phase harmonic propagation using Norton modified models and considering the real nature of unbalanced electric systems operation. © 2011 IEEE.

Real-time estimation of transmission line impedance based on modal analysis theory

The objective of this paper is to show a methodology to estimate the longitudinal parameters of transmission lines. The method is based on the modal analysis theory and developed from the currents and voltages measured at the sending and receiving ends of the line. Another proposal is to estimate the line impedance in function of the real-time load apparent power and power factor. The procedure is applied for a non-transposed 440 kV three-phase line. © 2011 IEEE.

Introduction of a non-conventional solution for Amazon transmission system: Analysis of the electric aspects

This article shows an analysis of the longitudinal electric parameters of a three-phase transmission line/section using a 280-meter high steel tower. This characteristic, the height of the line conductors and distance between them, are intrinsic related to the longitudinal and transversal parameters of the line. By this means, an accurate study was carried out in order to show the electric variations between a transmission line using the new technology and a three-phase conventional 440 kV line for a wide range of frequencies and a variable soil resistivity. In addition, by using a digital line model, simulations are carried out in time domain to analyze critical overvoltage transients on the studied line. © 2011 IEEE.

Research on photovoltaics: Review, trends and perspectives

This paper presents a briefly review, some trends and perspectives in the field of Photovoltaic energy conversion, which is considered to be the most important renewable energy source in few years, in the coming decades. The power electronics plays a fundamental role in this process, developing systems each times more competitive, efficient, reliable, and also reducing costs and reducing the payback time. Some trends are visible, which are the use of Silicon Carbide devices in PV inverters, the use of integrated inverter structures, the integration of power converters into the PV module or the use of few PV series connection, the development of thinner and more efficient solar cells. Moreover, the discussion about the necessity of MPPT and anti-island schemes are presented, mainly considering the expected growth of grid-tied applications. © 2011 IEEE.

Shunt active compensation based on the Conservative Power Theory current's decomposition

Considering the operation of shunt active compensators, such as active power filters, this paper proposes possible compensation strategies by means of the recent formulation of the Conservative Power Theory (CPT). The CPT current's decomposition results in several current components, which are associated with specific load characteristics (power transfer, energy storage, unbalances and/or non linearities). These current components are used for the definition of different compensation strategies, which can be selective in terms of minimizing particular disturbing effects. In order to validate the applicability of these new compensation strategies, simulation and experimental results for three-phase four-wire systems are presented. © 2011 IEEE.

Fluxo de potência trifásico probabilístico para redes de distribuição usando o método de estimação por pontos

In this paper the point estimation method is applied to solve the probabilistic power flow problem for unbalanced three-phase distribution systems. Through the implementation of this method the probability distribution functions of voltages (magnitude and angle) as well as the active and reactive power flows in the branches of the distribution system are determined. Two different approaches of the point estimation method are presented (2m and 2m+1 point schemes). In order to test the proposed methodology, the IEEE 34 and 123 bus test systems are used. The results obtained with both schemes are compared with the ones obtained by a Monte Carlo Simulation (MCS).

Practical comparisons among electronic energy meters, a precision energy meter and IEEE1459 for reactive energy measurements, under unbalanced and non-sinusoidal conditions

This paper presents a practical experimentation for comparing reactive/non-active energy measures, considering three-phase four-wire non-sinusoidal and unbalanced circuits, involving five different commercial electronic meters. The experimentation set provides separately voltage and current generation, each one with any waveform involving up to fifty-first harmonic components, identically compared with acquisitions obtained from utility. The experimental accuracy is guaranteed by a class A power analyzer, according to IEC61000-4-30 standard. Some current and voltage combination profiles are presented and confronted with two different references of reactive/non-active calculation methodologies; instantaneous power theory and IEEE 1459-2010. The first methodology considers the instantaneous power theory, present into the advanced mathematical internal algorithm from WT3000 power analyzer, and the second methodology, accomplish with IEEE 1459-2010 standard, uses waveform voltage and current acquisition from WT3000 as input data for a virtual meter developed on Mathlab/Simulink software. © 2012 IEEE.

A new design methodology for multipulse rectifiers with Delta auto-connected transformers and a retrofit application in Adjustable Speed Drives (ASDs)

Multipulse rectifiers can replace a conventional six pulse three-phase rectifier (diode bridge) providing a DC voltage with low ripple, low Total Harmonic Distortion of current (THDi) and a high Power Factor (PF). In this context is presented a multipulse rectifier with generalized Delta-differential autotransformer topology, which can provide any level of DC output voltage for any level of three-phase AC input voltage. This paper presents all the possible configurations for Delta topology in order to choose, through graphics, one configuration that presents reduced weight and volume. The average voltage on the DC bus must be compatible with the DC voltage in the six pulse rectifier used in commercial ASDs. Therefore, it is possible to apply the retrofit technique to replace the conventional bridge rectifier by the proposed multipulse rectifier. Based on mathematic models and simulation results, an 18-pulse rectifier with Delta topology, 220 V of line voltage, 315 V of DC output, and rating 2.5 kW of power was designed, implemented and applied for three different commercial ASDs. Experimental results as voltage and current waveforms and results about PF and THDi will be presented. © 2012 IEEE.

Speed estimation for induction motor using neural networks method

This work presents an alternative approach based on neural network method in order to estimate speed of induction motors, using the measurement of primary variables such as voltage and current. Induction motors are very common in many sectors of the industry and assume an important role in the national energy policy. The nowadays methodologies, which are used in diagnosis, condition monitoring and dimensioning of these motors, are based on measure of the speed variable. However, the direct measure of this variable compromises the system control and starting circuit of an electric machinery, reducing its robustness and increasing the implementation costs. Simulation results and experimental data are presented to validate the proposed approach. © 2003-2012 IEEE.

Decoupled reference generator for shunt active filters using the conservative power theory

Based on the framework of the Conservative Power Theory (CPT), this paper proposes some compensation strategies for shunt current compensators. CPT current decompositions result in several current-related terms associated with specific load characteristics, such as power consumption, energy storage, unbalances and load nonlinearities. These current components are decoupled (orthogonal) from each other and are used here to define different compensation strategies, which can be selective in minimizing particular effects of disturbing loads. Compensation strategies for single- and three-phase four-wire circuits are also considered. Simulated and experimental results are described to validate the possibilities and performance of the proposed strategies. © 2013 Brazilian Society for Automatics - SBA.

Desempeño de tanques decantadores de sólidos en un sistema de recirculación para producción de tilapia

To compare the removal efficiency of solids, turbidity and apparent color between a conventional and a column settling tanks in a recirculating aquaculture system (RAS) for tilapia farming. Materials and methods. Tilapia with a stocking density between 30 and 33 kg/m3 were cultured in a RAS consisting of a water level control box, PVC piping system, three plastic tanks for culture, conventional horizontal flow settling tank (Con.ST), column vertical flow settling tank (Col.ST), three phase fluidized bed reactor, oxygen transfer reactor, air compressor, air blower, centrifugal pump. The Con.ST operated at a volume of 1.4 m3 and hydraulic retention time (HRT) of 2.94 h; and was drained weekly for washing and sludge collection, representing a 55%discharge of system water volume. The Col.ST operated with a volume of 0.30 m3 and HRT of 0.553 h. Three daily partial draining operations were executed, representing a discharge of 50% of the system volume. Results. The mean solids removal efficiencies were: 34.01 and 44.44%for total solids; 64.45 and 71.71% for suspended solids; 21.10 and 45.65% volatile solids; 65.51% and 62.79% for turbidity; and 56.37 and 50.91% for apparent color, respectively for Con.ST and Col.ST. Conclusions. The two settling devices are useful on removal of the studied parameters and presented similar performance on turbidity and apparent color removal; however, the Col.ST was more efficient than Con.ST for solids removal, requires less space, less volume and requires less discharge water volume, displaying feasibility for its use on RAS.

Implementação de um controle digital para o compensador regenerativo de potência ativa

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Uma proposta de desenvolvimento de laboratório remoto de automação e acionamento de máquinas elétricas para uso didático, utilizando software open source

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Detecção e classificação de faltas de alta impedância em sistemas elétricos de potência usando lógica Fuzzy

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Proposta de diagnóstico para uso, instalação e descarte de transformadores de distribuição recuperados

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)