Jorge Luis Strack

Three-Phase Harmonic and Sequence Components Measurement Method Based on mSDFT and Variable Sampling Period Technique

This paper presents a three-phase harmonic and sequence components measurement method based on modulated sliding discrete Fourier transform (mSDFT) and a variable sampling period technique. The proposal allows measuring the harmonic components of a three-phase signal and computes the corresponding imbalance by estimating the instantaneous symmetrical components. In addition, an adaptive variable sampling period is used to obtain a sampling frequency multiple of the main frequency. By doing so, DFT typical errors, known as spectral leakage and picket-fence effect, are mitigated in steady state. The proposal is tested with different disturbances by simulation and experimental results. Some results obtained with a power quality monitor implemented with the proposed system are also presented. The high rejection to distortion in the electrical network, frequency adaptability, flexibility, and good performance in power quality monitor application render the proposed method a promising alternative for signal processing from the mains.

Evaluación y comparación de algoritmos de clasificación de eventos de tensión mediante su implementación en un DSP

This paper assesses the experimental implementation of three voltage events classification algorithms. They are known in the literature as symmetrical component algorithm, six-phase algorithm and space vector algorithm. They use the fundamental voltages and sequences components estimated by a sequence detector proposed by the authors previously. This detector is synchronized with the network achieving phase and frequency adaptation and high rejection to the network disturbances. From implementation of classification algorithm and detector on a DSP (Digital Signal Processor), the performance of each algorithm in the classification of real events and their possible application in a PQM (Power Quality Monitor) was evaluated.

Evaluation of voltage events detection methods

This work presents an comparison of some methods for voltage events detection. This evaluation is part of a wider study, which aims to develop a power quality monitor. Performance of evaluated methods is analyzed under demanding conditions, where the input signals present frequency variations, harmonic content and events of different magnitude, duration and initial phase. The conclusions of this analysis are the basis for the choice of the best suited methods for a real application.

Evaluation of three-phase voltage dips classification algorithms based on computational intelligence

In this paper are evaluated three different three-phase voltage dip classification algorithms developed by the authors. All them are based in the information provided by a sequence detector developed in a previuos work. The first algorithm is a logical classifier, the second it is based on fuzzy logic, and the third algorithm is a neural network adequately trained for this purpose. This evaluation is part of a wider work, and it will be used to the potential development of a power quality monitor. The performance of the algorithms under test in the classification of voltage dips, in ideal conditions and with variations in the phase and frequency, and high harmonic content is assessed. The conclusions of this analysis are the basis for the development and implementation of some of the functions of this instrument.

Análisis de la calidad de la energía en un centro de cómputos

Este trabajo analiza el impacto que provoca, sobre los indices de calidad de la energia electrica, un numero importante de cargas no lineales pertenecientes a un centro de computos y conectadas a una red trifasica. Se presenta una metodologia computacional simple que puede ser utilizada para analizar los efectos provocados por cargas con indices importantes de distorsion. Distintos modelos de computadoras personales (PCs), monitores e impresoras fueron ensayados en laboratorio a los efectos de registrar las senales de corriente y sus principales parametros electricos. Con estos resultados y con la asistencia del programa ATP (Alternative Transient Program) se simularon modelos equivalentes de los equipos para evaluar los diferentes fenomenos que provocan los componentes armonicos de corriente. Los efectos de atenuacion y diversidad son analizados considerando distintos escenarios: modelos de PCs identicas pero en distintos regimenes de funcionamiento, PCs combinadas con monitores e impresoras. Se demuestra en las simulaciones que una importante mitigacion natural de armonicos se produce debido a las variaciones en los indices de distorsion armonica de corrientes de los aparatos estudiados y a la propia impedancia de la linea de alimentacion. Se han registrado en determinadas combinaciones de equipos reducciones del THDI del 14% y de un 40% en funcion de la relacion reactancia inductiva-resistencia de la linea de alimentacion. Los resultados simulados fueron contrastados con mediciones en el centro de computos de una empresa de servicios publicos, con 120 PCs distribuidas en una red trifasica. El seguimiento se realizo con un analizador de redes a lo largo de una semana, registrando corrientes de lineas, indices de distorsion de corrientes y tensiones con sus correspondientes componentes armonicos.