Showing papers by "Moises V. Ribeiro published in 2011"

Improved Disturbance Detection Technique for Power-Quality Analysis

Abstract: This paper presents an improved technique for detecting disturbances in voltage signals for power quality analysis. The main advantage of the proposed technique lies in its capability to detect disturbances when power frequency is time-varying. In addition, the technique is capable of detecting disturbances in frames corresponding to 1/64 of the fundamental component. Simulation results indicate that the proposed technique can offer improved performance in comparison with previous one.

Enhanced demodulation-based technique for estimating the parameters of fundamental component in power systems

Abstract: The recent introduction of smart grid concepts in power systems demands metering and monitoring equipments with great deal of flexibility. To achieve this, one heavily depends upon new generation of signal processing tools. Regarding low-cost and effective signal processing-based techniques for parameters estimation in smart grids, the estimation of power components when frequency deviates from its nominal value is a timely and important issue to be addressed. The authors outline a demodulation-based technique for estimating the amplitude, phase and frequency of the fundamental component of a power line signal. This technique makes use of a finite impulse response filter design method that efficiently allocates zeros over the unit circle of the z-plane so that the performance losses yielded by power frequency deviations can be minimised if the signal is corrupted by harmonics. Numerical results indicate that the proposed technique outperforms previous ones and can be a good candidate for measurement and monitoring in flexible power systems.

A low cost STBC-OFDM system with improved reliability for power line communications

Abstract: This paper outlines the use of symbol repetition technique together with space time block code orthogonally frequency division multiplexing (STBC-OFDM) scheme for power line communication (PLC) when the receiver has complete knowledge about the channel state information. Due to redundancy in the proposed technique, a low-complex FFT can be implemented. Also, the way as the symbol diversity is explored, which can offer similar improvement found in space diversity, can improve the performance of STBC-OFDM scheme if the PLC channel is frequency-selective and corrupted by impulsive like noise, such as the additive impulsive Gaussian noise (AIGN). Simulation results reveal that the STBC-OFDM with a simple symbol repetition technique offers an enhanced reliability, compared to a regular STBC-OFDM when Alamouti code is considered.

A low cost OFDM based modulation schemes for data communication in the passband frequency

Abstract: This contribution presents low computational complexity versions of orthogonal frequency division multiplexing (OFDM) modulation scheme for the implementation of clustered-OFDM systems for data transmission in the passband frequency. Among the proposed schemes, which are named Hermitian symmetric OFDM (HS-OFDM) I and HS-OFDM II, the HS-OFDM II can offer computational complexity reduction in comparison with the single side-band OFDM (SSB-OFDM), OFDM, and HS-OFDM systems when the length of the OFDM symbol increases. Results show that all simulated schemes can provide the same BER performance in PLC channel. Additionally, HS-OFDM I has a lower complexity than traditional HS-OFDM, and HS-OFDM II further reduces the complexity and achieves the lowest complexity implementation among the five schemes.

Sistema automático de classificação de distúrbios elétricos múltiplos e isolados

Abstract: Neste trabalho, um sistema de classificacao de disturbios eletricos multiplos e isolados e proposto. A inovacao deste sistema esta na utilizacao de um conjunto de filtros no pre-processamento, o que possibilita a separacao de algumas classes de disturbios e, consequentemente, a classificacao de disturbios multiplos a partir de classificadores mais simples. O sistema proposto foi projetado com dados simulados e testado tanto com dados simulados quanto com dados reais. Bons resultados foram alcancados, uma vez que um desempenho global superior a 99% foi obtido, para o conjunto de dados considerado.