Ramón I. Diego

Analysis of Harmonics in Power Systems Using the Wavelet Packet Transform

The paper proposes an algorithm based on the wavelet-packet transform for the analysis of harmonics in power systems. The algorithm proposed decomposes the voltage/current waveforms into uniform frequency bands corresponding to the odd harmonic components of the signal. First, the selection of the mother wavelet, the sampling frequency and the frequency characteristics of the selected wavelet filter bank are studied. Finally the performance of the method proposed is compared with the results obtained using DFT analysis and the harmonic group concept introduced by the International Electrotechnical Commission using different test waveforms proposed in standard IEC-61000-4-7

Application of the wavelet-packet transform to the estimation of harmonic groups in current and voltage waveforms

This paper presents a method to estimate the harmonic groups in voltage and current waveforms using the wavelet-packet transform. The wavelet-packet decomposition algorithm is selected to obtain output bands compatible with the harmonic groups defined in the harmonics measurement standards for power-supply systems. The method proposed is analyzed in the measurement of harmonic components, either synchronized or nonsynchronized, with the fundamental power frequency, comparing the results with the method proposed in the international standards.

Applications of Wavelet Transform for Analysis of Harmonic Distortion in Power Systems: A Review

Wavelet transform (WT) is one of the most useful digital signal processing tools for time-frequency analysis of power quality disturbances in power systems. This paper presents an extensive bibliographic review of applications of WTs in the measurement and analysis of harmonic distortion in power systems, discussing the performance of the different methods proposed in the technical literature.

On the use of the Hanning window for harmonic analysis in the standard framework

This paper studies the effect of the Hanning window (HW) on the processing of harmonics and interharmonics in the framework of the standard defined by the IEC. The performance of the HW is studied both in the processing of a large harmonic current fluctuation and when an interharmonic voltage component appears between two contiguous harmonic components. The results obtained are compared with the results obtained when applying the method defined in the standard and the root mean square value of each signal.

Measurement of Subharmonics in Power Voltages

This paper presents the results of the monitoring of subharmonic voltages in a low-voltage distribution network using an IEC harmonic measurement instrument. The time evolution and the statistical analysis of the r.m.s. voltage magnitude of the subharmonic group and subgroup, defined as grouping of the output bins of an IEC harmonic measurement instrument below 50 Hz, are investigated in a low-voltage distribution system. The results obtained show higher magnitude of these components than was expected, showing similar time evolution to the magnitudes of the 1st and 2nd order interharmonic groups and the flicker severity indices simultaneously measured in the same power supply system.

Voltage notch detection and analysis using wavelets

This paper presents a low-cost virtual instrument for detection and analysis of voltage notches in voltage supply using wavelets. A simple wavelet decomposition tree has been used for detection and analysis of the two main features of voltage notching: the transients associated with the beginning and the end of the commutation notches and the stationary high-frequency components of the spectrum of the signal. The results obtained show the performance of the method proposed in the detection and analysis of the time-frequency characteristics of voltage notching.

Power System Basics for Bussiness Professionals

This letter shows the effects of harmonics in the voltage supply on the voltage tolerance of equipment. Several laboratory tests have been made to obtain the voltage tolerance curves of a personal computer using a pure sinusoidal voltage supply and under different nonsinuoidal conditions. The analysis shows that the voltage tolerance of the equipment used in the test depends on both the voltage harmonic distortion magnitude and the phase difference between harmonics, with the equipment being more sensitive to low order harmonics.

Rapid Voltage Changes in Power System Networks and Their Effect on Flicker

A rapid voltage change (RVC) is a type of power-quality (PQ) disturbance that has not received sufficient attention in the international PQ standards. Presently, EC 61000-4-30, Ed. 3, defines a precise method for RVC detection and analysis. RVCs can cause or contribute to flicker. However, the existing studies on the subject have not found a correlation between the short-term flicker severity index Pst and the parameters of an RVC event. This paper provides an interpretation of this lack of correlation and shows that instead there is a correlation of RVC events with the instantaneous flicker sensation Pinst. This work is based on the analysis of both simulated waveforms containing RVCs and waveforms recorded in low-voltage and medium-voltage locations.

A Discussion of New Requirements for Measurement of Harmonic Distortion in Modern Power Supply Systems

This paper discusses some of the new requirements in the measurement of harmonic distortion in modern power supply systems: the measurement of the distortion over the harmonic range (>2 kHz) and the time-frequency analysis of harmonic distortion, and presents the basic performance of a new advanced digital measurement instrument that, in addition to classical harmonic distortion, provides an extended analysis of the distortion in the time-frequency domain.

Review of signal processing techniques for detection of transient disturbances in voltage supply systems

This paper presents a review of some of the most commonly used signal processing techniques for detection and extraction of transient disturbances in voltage supply systems. The performances of different time-domain and frequency-domain methods are compared using different test signals. The advantages and disadvantages of each method are discussed highlighting the potential of each method according to the application.