Sharif Digital Repository

This paper presents the results of a power quality survey in a distribution system. More than fifty nodes are selected and monitored. Power quality indices are extracted based on IEEE and IEC Standards. The evaluation includes field data collection, extraction of statistical power quality indices and comparing the results against standard limits. Experimental data as well as clarifying tables and graphs are presented. The results are then discussed to evaluate the strength and weaknesses of applying standard limits when real observations are to be performed. Some proposals are also made in order to make standard procedures and limits more effective based on practical observations. © 2007,... 

This paper presents the results of a thorough power quality analysis in order to determine the cause of failure in a Compressed Natural Gas (CNG) distribution transformer. The paper presents the field data and determines power quality indices of such loads based on IEEE/IEC standards. It provides steady state time-series parameters as well as transient waveforms. Different signatures of the voltage and current signals are extracted, and consequences of the distortions are described. The analysis is clarified by presenting both time domain captured waveforms and statistical power quality indices. Optimum solution for improving power quality and prevent component failure is also proposed. ©... 

These days the number of nonlinear loads in power systems is increasing dramatically. These nonlinear loads inject harmonic currents and the voltages. Accordingly, the modeling of these loads and analysis of their effects on power quality has gained much attention. This paper presents harmonic models for residential appliances. The model is based on Norton equivalent technique. The parameters of appliances models are determined using measurements. These models are then verified by comparison with the measurements results for each load. Based on the developed individual loads, an estimate for a household/an office customer is found and the harmonic content for such customers is estimated. An... 

This paper presents an effective hybrid optimal modulation technique for a cascaded H-bridge (CHB) multilevel inverter. The introduced method is generalized optimal pulsewidth modulation, which can be extended to any m-level CHB multilevel inverter operating at any switching frequency. The presented hybrid optimal modulation strategy includes the pattern exchange and optimal modulation techniques. In the optimal modulation technique, the hybrid interior-point algorithm, which is more flexible and efficient than conventional optimization techniques, is applied. The proposed hybrid optimal modulation strategy yields balanced units' output fundamental voltages, and low total harmonic distortion... 

In this paper, an analysis of the harmonic contents of the optical output power for an in-plane single mode laser diode is performed, and the results are described in detail. In the first step, the absolute value of power for each harmonic is obtained in terms of various laser diode parameters, and the variations of external parameters, such as modulation current, bias current and frequency, are discussed. The analysis is done by direct solution of the rate equations of an arbitrary laser diode for carrier and photon densities. It is known that the optical power has a nonlinear dependence on frequency, and the maximum optical power of each harmonic is attained in its resonance frequency. The...