Showing papers by "Mohammed Abo-Zahhad published in 2007"

A hybrid ECG compression algorithm based on singular value decomposition and discrete wavelet transform.

Abstract: Increasing use of computerized ECG processing systems requires effective electrocardiogram (ECG) data compression techniques which aim to enlarge storage capacity and improve data transmission over phone and internet lines. This paper presents a compression technique for ECG signals using the singular value decomposition (SVD) combined with discrete wavelet transform (DWT). The central idea is to transform the ECG signal to a rectangular matrix, compute the SVD, and then discard small singular values of the matrix. The resulting compressed matrix is wavelet transformed, thresholded and coded to increase the compression ratio. The number of singular values and the threshold level adopted are based on the percentage root mean square difference (PRD) and the compression ratio required. The technique has been tested on ECG signals obtained from MIT-BIH arrhythmia database. The results showed that data reduction with high signal fidelity can thus be achieved with average data compression ratio of 25.2:1 and av...

C0mprehensive newton-raphson model for incorporating unified power flow controller in load flow studies

Abstract: Flexible AC Transmission Systems FACTS include unified power flow controllers (UPFC). Incorporation of a UPFC by a comprehensive Newton-Raphson power flow model into an existing MATLAB NewtonRaphson power flow algorithm is the subject of this paper. Unlike existing UPFC models available in open literature, this UPFC power flow model is modified to set control of active and reactive powers and voltage magnitude in any combination or to not control all of them. A set of analytical equations has been derived to provide better UPFC initial conditions. Their solution algorithm exhibits quadratic or near quadratic convergence characteristics. Based on this model, it is possible to estimate the UPFC control variables and the UPFC converters ratings. Also the effects of the UPFC coupling transformers impedances on the UPFC control variables and converters ratings are clarified and highlighted.

Injection power upfc model for incorporation of unified power flow controller in load flow studies

Abstract: This paper is devoted to the incorporation of the s teady-state model of the unified power flow controller (UPFC) in power flow programs using a UPFC injection model. The adopted UPFC injection mo del is based on the representation of UPFC in steady-state conditio ns by two voltage sources in series with certain reactances. Using th is UPFC power flow model, the effects of UPFC control variables on sys tem voltage magnitude, line active and reactive power flow, tot al system losses, slack bus generated active and reactive power and the inj ected reactive power from voltage controlled buses are illustrated. Also , the effects of the UPFC location and the UPFC series converter couplin g transformer reactance on power flows and on total system real p ower loss are studied. It is found that using this UPFC power flow model i t is possible to show the power flow characteristics inside the UPFC conv erters, themselves.