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Parameter Optimization of Shunt FACTS Controllers for Power System Transient Stability Improvement
Get PDFTo enhance power system transient stability, shunt FACTS devices can be controlled in discontinuous mode or in a combination of discontinuous and continuous mode. In continuous mode proportional controller is usually used. This paper investigates the performance of others controllers in continuous mode. Two additional controllers – PI and lead-lag, have been considered. Controller parameter values have been optimized for minimum settling time. This study shows that both PI and lead-lag controllers have good potential for improving critical clearing time. It also shows that properly selected controller parameter values can reduce settling time significantly. The obtained results are verified using non-linear time-domain simulation for both single-machine infinite-bus (SMIB) and multi-machine (10 machine 39 bus) case
Approximation Techniques For Analytical Characterization Of Downlink Traffic Power For Multi-Service CDMA Networks
Get PDFThis paper presents a novel analytical framework for characterizing the downlink power allocations for a multi-rate Code Division Multiple Access (CDMA) network. The characterization takes into account the RF propagation model, the shadowing process and considers both intracell and intercell interference. To arrive at the model, the paper utilizes approximation techniques recently developed in the recent literature to evaluate the sum of lognormal random variables. The overall traffic power is modeled as a random variable that is function of the network parameters and the assigned downlink bit rates. The paper demonstrates the calculation of the forward link power outage probability as one example application for the developed characterization. It also compares between two approximation techniques suggested in this paper: matched first and second order statistics, and the min-max technique. The analytical results are compared to those obtained via Monte-Carlo simulations to assess the accuracy of the adapted approximations. The results indicate the min-max technique produces more accurate results when compared to matched first and second moments approximation scheme
Downlink Traffic Power Characterization for Multi- Rate Wireless CDMA Data Networks
Get PDFThe characterization of downlink traffic power is an important issue for the design of efficient call admission control (CAC) and radio resource management (RRM) procedures. In this paper an analytic model is presented to solve the power-rate assignment problem and to approximate the probability distribution function for the cell site downlink traffic power for a multi-rate CDMA based network. The model accounts for both the radio frequency propagation model and the large signal variations represented by the signal shadowing process. As one application, the model is utilized in calculating the probability of cell site power outage as a function of the system rates and the number of supported bursts. The study compares between model based results and results obtained using conventional Monte- Carlo simulations. Comparisons indicate the model provides an adequate approximation for outage probability figure
Convergence and steady-state analysis of the normalized least mean fourth algorithm
Get PDFThe normalized least mean-fourth (NLMF) algorithm is presented in this work and shown to have potentially faster convergence. Unlike the LMF algorithm, the convergence behavior of the NLMF algorithm is independent of the input data correlation statistics. Sufficient conditions for the NLMF algorithm convergence in the mean are obtained and an analysis of the steady-state performance is carried out with a new approach. The latter uses the concept of feedback and bypasses the need for working directly with the weight error covariance matrix. Simulation results obtained in a system identification scenario confirms the theoretical predictions on performance of the NLMF algorithm
A Novel Nonparaxial Time-Domain Beam-Propagation Method for Modeling Ultrashort Pulses in Optical Structures
No full textIn this paper, a new nonparaxial time-domain beam-propagation method (TD–BPM) based on Padé approximant for modeling ultrashort optical pulses has been proposed and verified. The high efficiency of the technique in modeling long device interaction comes from solving the TD wave equation along one direction and allowing the time window to follow the evolution of the pulse. The accuracy of the method was tested in three different environments of homogenous and nondispersive medium, metallic, and dielectric waveguides and then was applied to model ultrashort pulse propagation in a directional-coupler device. The characterization of the technique shows excellent performance in terms of accuracy, efficiency, and stability, which the conventional paraxial TD–BPM failed to achieve. The new TD–BPM is particularly well suited for the study of unidirectional propagation of compact ultrashort temporal pulses over long distances in waveguide structures
"Harmonic and intermodulation performance of the semiconductor bolometer"
Get PDFA mathematical model for the temperature dependence of the bolometer semiconductor resistance is presented. The model, basically a sine-series function, can easily yield closed-form expressions for the harmonic and intermodulation performance of the acquired interferogram voltage with large-amplitude multisinusoidal variations in the incident radiation. The special case of two-tone equal-amplitude incident radiation is considered in detail. The results show that the intermodulation components are always higher than the harmonic components of the same order. The results also show that the second-order intermodulation is always dominant and is higher than the second-harmonic component by about 6 dB. Moreover, the results show that for relatively small incident amplitudes of the incident radiation the ratio between the second- and third-harmonic components is almost equal to the ratio between the second-harmonic component and the fundamental. The results also show that the ratio between the amplitudes of the second- and third-order intermodulation components is almost equal to the ratio between the amplitudes of the second-order intermodulation component and the fundamental
PARALLEL COMPUTING PLATFORM FOR EVALUATING LDPC CODES PERFORMANCE
Get PDFThis paper presents a novel approach for the design and implementation of a simulation platform for evaluating LDPC codes performance. The existing LDPC code simulation tools consume very long time in evaluating the performance of a specific code design. This is due to the intensive number of required computations. This problem is overcome by developing a parallel protocol to distribute the computations among processing nodes in a TCP/IP network. As indicated by experimental results, the proposed simulation platform is scalable with the number of processing nodes. Another practical advantage of the proposed system is that it does not need dedicated processors to run it; rather, it can utilize idle times of processing nodes in a network and work transparent to a node user. Furthermore, network daemons are used to utilize network nodes even if they are in the log-off state
Large signal performance of micromachined silicon condenser microphones
Get PDFA mathematical model for the open-circuit output voltage of a micromachined silicon condenser microphone with a single deeply corrugated diaphragm as a function of the applied acoustic pressure is presented. The model, basically a sine-series function, can easily yield closed-form expressions for the amplitudes of the output components resulting from a multisinusoidal input acoustic pressure. The special case of an equal-amplitude two-tone acoustic pressure input is considered in detail. The results show that the microphone generates only odd-order harmonic and intermodulation products. The results also show that the amplitudes of these components are strongly dependent on the microphone parameters, the corrugation depth and the ratio between the half-length of the diaphragm and its thickness. Moreover, the results show that the acoustic pressure required to produce a pre-specified output open-circuit voltage is strongly dependent on these parameters
Prediction of Gain Expansion and Intermodulation Performance of Nonlinear Amplifiers
Get PDFA mathematical model for the input-output characteristic of an amplifier exhibiting gain expansion and weak and strong nonlinearities is presented. The model, basically a Fourier-series function, can yield closed-form series expressions for the amplitudes of the output components resulting from multisinusoidal input signals to the amplifier. The special case of an equal-amplitude two-tone input signal is considered in detail. The results show that unless the input signal can drive the amplifier into its nonlinear region, no gain expansion or minimum intermodulation performance can be achieved. For sufficiently large input amplitudes that can drive the amplifier into its nonlinear region, gain expansion and minimum intermodulation performance can be achieved. The input amplitudes at which these phenomena are observed are strongly dependent on the amplifier characteristics