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1

On the use of multi-harmonic least-squares fitting for THD estimation in power quality analysis

Ramos P. M., Janeiro F. M., Radil T.

Metrology and Measurement Systems

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2012

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Vol. 19, nr 2

295-306

EN

The quality of the supplied power by electricity utilities is regulated and of concern to the end user. Power quality disturbances include interruptions, sags, swells, transients and harmonic distortion. The instruments used to measure these disturbances have to satisfy minimum requirements set by international standards. In this paper, an analysis of multi-harmonic least-squares fitting algorithms applied to total harmonic distortion (THD) estimation is presented. The results from the different least-squares algorithms are compared with the results from the discrete Fourier transform (DFT) algorithm. The algorithms are assessed in the different testing states required by the standards.

2

Comparative analysis of three algorithms for two-channel common frequency sinewave parameter estimation: ellipse fit, seven parameter sine fit and spectral sinc fit

Ramos P. M., Janeiro F. M., Radil T.

Metrology and Measurement Systems

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2010

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Vol. 17, nr 2

255-270

EN

In this paper, a comparison analysis of three different algorithms for the estimation of sine signal parameters in two-channel common frequency situations is presented. The relevance of this situation is clearly understood in multiple applications where the algorithms have been applied. They include impedance measurements, eddy currents testing, laser anemometry and radio receiver testing for example. The three algorithms belong to different categories because they are based on different approaches. The ellipse fit algorithm is a parametric fit based on the XY plot of the samples of both signals. The seven parameter sine fit algorithm is a least-squares algorithm based on the time domain fitting of a single tone sinewave model to the acquired samples. The spectral sinc fit performs a fitting in the frequency domain of the exact model of an acquired sinewave on the acquired spectrum. Multiple simulation situations and real measurements are included in the comparison to demonstrate the weaknesses and strong points of each algorithm.

3

Four-Parameter Sine-Fitting Algorithm for Detection and Classification of Transients and Waveform Distortions

Ramos P. M., Radil T., Cruz Serra A.

Metrology and Measurement Systems

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2008

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Vol. 15, nr 4

441-456

EN

This paper describes a new method for detection of some power quality (PQ) disturbances, namely transients and waveform distortions. The proposed algorithm is based on a modified version of the four-parameter sine-fitting algorithm. The sine-fitting algorithm is used to estimate the parameters of the power system's voltage signal's fundamental and to extract the transient component of the voltage. The performance of the proposed method is compared with previously developed algorithm and with two commercial PQ analyzers.

4

DSP based power quality analyzer for detection and classification of disturbances in a single-phase power system

Radil T., Ramos P. M., Janeiro F. M., Cruz Serra A.

Metrology and Measurement Systems

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2007

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Vol. 14, nr 4

483-494

EN

This paper describes the prototype of a power quality analyzer designed for real-time detection and classification of disturbances that occur in a single-phase power system. The standalone DSP-based analyzer implements previously developed algorithms for detection and classification of power quality disturbances such as transients, waveform distortions, sags, swells and interruptions. Its performance was verified during long term monitoring of the power system.