Julio Barros

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.

Automatic Detection and Analysis of Voltage Events in Power Systems

This paper presents an automatic system for real-time detection and analysis of voltage events in power systems. The voltage events considered are those that cause a temporary increase or decrease in the rms voltage magnitude over the limits recommended in the international standards. The system proposed uses three Kalman filters to detect when a voltage event begins and to estimate the three-phase voltage supply during the event. The results obtained from real measurements in a low-voltage distribution network show that the system accurately detects and analyzes in real time different types of voltage events in power systems

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.

An adaptive method for determining the reference compensating current in single-phase shunt active power filters

This letter proposes an adaptive method, based on a Kalman filter, to obtain the reference compensating current in single-phase shunt active power filters. The results obtained using a digital signal processor-based laboratory setup improve the dynamic performance of the active filter because it is able to compensate in real-time, the harmonic components in the load current. The method proposed can also compensate the phase error in the harmonic components produced by the discrete sampling and the execution time delay associated with digital systems.

A Proposal for On-Line Detection and Classification of Voltage Events in Power Systems

This paper presents a new method for online real-time detection and classification of voltage events in power systems. The method proposed simultaneously uses the results obtained in the application of the discrete wavelet transform and an extended Kalman filtering to the voltage waveform. Wavelet analysis is used for detection and estimation of the time-related parameters of an event and the extended Kalman filtering is used for confirmation of the event and for computation of the voltage magnitude during the event. The paper presents different experimental results showing the improved performance of this combined approach.

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.

Voltage Event Detection and Characterization Methods: A Comparative Study

The paper presents a comparative study of the most commonly used methods of detection and analysis of voltage events in power systems. The performance of the rms method, the fundamental component estimation using discrete Fourier transform and Kalman filtering and the use of wavelet analysis for detection and estimation of magnitude and duration of voltage events, are studied under simulation using voltage dips of different magnitude, duration and point-on-wave of beginning in a pure sinusoidal voltage supply and also for a voltage supply with different harmonic distortion levels. The methods employed are also tested using real voltage events measured in a low voltage distribution system discussing the results obtained

A combined wavelet - Kalman filtering scheme for automatic detection and analysis of voltage dips in power systems

A combined wavelet analysis - Kalman filtering approach is presented in this paper for the automatic detection and analysis of voltage dips in power systems. Wavelet analysis is used to process the voltage waveform for detection and better estimation of the time-related parameters of a voltage dip in voltage supply, while Kalman filtering is used for the estimation of voltage magnitude and phase angle during the event. The method proposed, which can be processed in real-time, has been tested both by computer simulations and experimentally using measurements from a low voltage distribution system, showing the potential of this combined scheme for complete and accurate characterization of voltage dips in power systems.

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.