Search results for "distortion"
showing 10 items of 309 documents
Static meters for the reactive energy in the presence of harmonics: an experimental metrological characterization
2009
Electricity metering plays a crucial role for all the commercial transactions on the energy market. Thus, an accurate evaluation of the performance of the electricity metering equipment is required not only in the reference operating conditions but also in the presence of disturbances affecting the power systems. As regards this matter, this paper analyzes the main aspects related to the metrological characterization of the static meters for the reactive energy in the presence of harmonic distortion. Attention is focused not only to the meters covered by the current standards but also to the meters of better accuracy and to the reference standard meters. The analysis is supported by several…
A New Measurement Method for the Detection of Harmonic Sources in Power Systems Based on the Approach of the IEEE Std. 1459–2000
2010
In this paper, a novel single-point strategy is proposed for the detection of the harmonic sources in power systems. The method is an improvement of a strategy previously proposed by the authors; it is developed from the IEEE Std 1459-2000 approach and it can be entirely implemented in the time domain, thus simplifying the measurement system. The effectiveness of the proposed method is evaluated by introducing simple decision-making rules and by taking the presence of the measurement transducers into account. Several simulations and experimental tests are presented, showing that the enhanced strategy is able to give an useful information on the detection of the dominant harmonic source upst…
A PC-based wattmeter for accurate measurements in sinusoidal and distorted conditions: Setup and experimental characterization
2012
This paper presents the development of a high-accuracy sampling wattmeter, which can be employed with both sinusoidal and distorted input signals. The proposed personal computer (PC)-based system is a simple, portable, and low-cost solution because it is based on two commercial data acquisition boards connected to a common PC. Owing to this solution, the voltage is sensed directly, avoiding expensive voltage dividers, while the current is sensed by means of a noninductive current shunt. Commercial software is also used for data processing and implementation of the virtual instrument. The setup of the PC-based wattmeter is described, with a detailed description of the correction strategy of …
Phase Margin Degradation of a Peak Current Controlled Converter at Reduced Duty Cycle
2010
An inner current loop is frequently used in many switching power supplies to achieve higher stability and a good current sharing. Nevertheless, some problems derived from its practical implementation can be encountered. One problem is related to the need of filtering of the sensed current and was discovered by the authors in the implementation of a 500 W converter, when peak current control was applied by sensing the switch current. This paper will demonstrate mathematically that an RC filter not only filters out the noise but also can cause a degradation of the phase margin, especially, if the needed duty cycle is close to zero. The main reason for it is the severe distortion of the curren…
Medición del efecto látigo en redes de suministro
2016
La variabilidad de la demanda que se origina de un agente a otro en la cadena de suministro, aumenta o amplifica a medida que la señal se aleja del punto de origen; estas distorsiones se denominan Efecto Látigo. En este artículo se aborda una red de suministros multieslabón, que estima los intervalos de medición de la distorsión de la demanda de la red, de acuerdo a comportamientos extremos en el sistema que permiten diagnosticar su desempeño en términos de la amplificación de demanda. Para la investigación se aplican mediciones estáticas locales y globales del efecto látigo, en cada nivel de la red de suministros del juego de la cerveza de cuatro eta-pas; cada etapa o eslabón tiene múltipl…
Impact of integrating photovoltaic based DG on distribution network harmonics
2017
The process of integrating various distributed generation (DG) technologies in power system networks is increasing rapidly in the recent years. One major concern about the integration of DGs is their impact on network harmonics. The aim of this paper is to investigate the effects caused by the integration of photovoltaic DG in distribution networks on system harmonics. The penetration level, number of DG units, and their location are used as parameters in order to verify the effects of DG on system harmonics. Moreover, a study of single and double tuned filters is conducted as harmonics mitigation techniques. Detailed simulations using Matlab/Simulink are inserted in order to explain and ve…
Improvement of Hall Effect Current Transducer Metrological Performances in the Presence of Harmonic Distortion
2010
The performance of Hall effect current transducers (HECTs), under distorted waveform conditions, is usually characterized by means of a frequency response test. In this paper, it was investigated if frequency response is able to correctly evaluate the ratio and the phase errors under distorted conditions. Two HECTs, with the accuracy class level of 1% and 0.5%, respectively, were experimentally characterized under two conditions: 1) sinusoidal excitation with frequencies ranging from 50 to 750 Hz, which is the well-known frequency response test, and 2) nonsinusoidal excitation using fundamental frequency and one harmonic with adjusted amplitude and phase shift. It was found that ratio and p…
Frequency response of Measurement Current Transformers
2008
In this paper the frequency response of two CTs is experimentally evaluated in the range of 30-600 Hz. A theoretical analysis of CTs behavior has been developed by means of the equivalent circuit. It was shown, by an experimental test, that, for the frequency range analyzed, the transformer equivalent circuit is a valid tool for the evaluation of CT performances.
Subjective image fidelity metric based on bit allocation of the human visual system in the DCT domain
1997
Until now, subjective image distortion measures have partially used diverse empirical facts concerning human perception: non-linear perception of luminance, masking of the impairments by a highly textured surround, linear filtering by the threshold contrast frequency response of the visual system, and non-linear post-filtering amplitude corrections in the frequency domain. In this work, we develop a frequency and contrast dependent metric in the DCT domain using a fully non-linear and suprathreshold contrast perception model: the Information Allocation Function (IAF) of the visual system. It is derived from experimental data about frequency and contrast incremental thresholds and it is cons…
Analysis of Fresnel Zone Plates Focusing Dependence on Operating Frequency
2017
[EN] The focusing properties of Fresnel Zone Plates (FZPs) against frequency are analyzed in this work. It is shown that the FZP focal length depends almost linearly on the operating frequency. Focal depth and focal distortion are also considered, establishing a limit on the frequency span at which the operating frequency can be shifted. An underwater FZP ultrasound focusing system is demonstrated, and experimental results agree with the theoretical analysis and simulations.