فصلنامه روشهای هوشمند در صنعت برق
پیاپی 20 (زمستان 1393)

A fault tree illustrates the ways through which a system fails. It states different ways in which combination of faulty components result in an undesired event in the system. Being used in phases such as designing and exploiting industrial systems، and the designers able to evaluate the dependability attributes such as reliability، MTTF and sensitivity. In addition، in the mentioned ability، the fault tree is a systematic method for finding systems bottlenecks and weakness point. In spite of its extensive use in evaluating the reliability of systems، fault tree is rarely used in calculating sensitivity. In the last decade، few researches has been conducted in this field، however these methods are not applicable to large scale systems and are not systematic. This paper provides a systematic method for evaluating system sensitivity through fault tree. Then، it introduces sensitivity of NMR architecture as one of the common structures of fault tolerance which is used for enhancing systems’ reliability، safety and availability in industry. This article presents a comprehensive and parameterized formula for NMR structure''s sensitivity. The presented method can be a great help for designing and exploiting reliable systems engineers in systematic and instant calculation of sensitivity by means of fault tree.

This paper analyses the Partial Discharge (PD) on the stator terminals of synchronous generator. This is necessary to collect experimental data for the analysis. First، exploiting the measurement devices، special signals that describe the partial discharges are repeatedly collected. Then، based on the current standards، the collected empirical data are subjected to interpretation. To ease the interpretation process، an Artificial Neural Network is trained and validated. We have used a double layers forward perceptron neural network which is trained by Levenberg–Marquardt algorithm that utilizes least square method as the performance index. As the case study، three gas turbine-generators located in Shahre-Rey power plant (Rey Power Generation Management Company) have been subjected to repeatedly data collection. The mentioned generators are manufactured by Mitsubishi with 85 MW of nominal power. Generally، partial discharge analysis has the following practical implication about the probable defects: lamination of the internal terminal، mobility within the main insulation and discharge into the groove in stator of synchronous generator.

In this paper، we implement real irregular terrain model in computer program by using image processing. We show how this approach can be used in simulation of E. M. wave propagation on irregular earth’s surface in a realistic manner. Some simulations are performed for implementation of longitudinal height differences over the propagation path as PEC surface. We also describe that how this approach can be used for any boundary condition in computational space. The results observed in Snapshots of the field profiles taken at different simulation times، validates capability of this method.

Economic and environmental conditions often make large stations and transmission lines، restrictions are placed. Small and medium-sized production units connected to existing systems as a strategy is in progress. These units are usually near the center of the load placed and distributed generators (DG) famous are the DG are allowed types vary، such as induction generators rack squirrel-connected wind turbines، generators fed induction double mounted wind turbines، fuel cells connected to the system by power electronic converters or synchronous generator connected to the turbine combustion [10]. This way sensitivity analysis in systems of distributed generation (DG) is assessed. It is shown that the method can detect the effect of control parameters listed wind turbine connected to a double-fed induction generator (DFIG) Badoou the impedance of the changing the speed of on the stability of the transmission line useful system invested. The control parameters of the importance of influencing the behavior of DFIG are divided.

Fractional-order PID (FOPID) controller is a generalization of standard PID controller using fractional calculus. Compared with the Standard PID controller، two adjustable variables “differential order” and “integral order” are added to the PID controller. Three tank system is a nonlinear multivariable process that is a good prototype of chemical industrial processes. Cuckoo Optimization Algorithm (COA)، that was recently introduced has shown its good performance in optimization problems. In this study، Improved Cuckoo Optimization Algorithm (ICOA) has been presented. The aim of the paper is to compare different controllers tuned with a Improved Cuckoo Optimization Algorithm (ICOA) for Three Tank System. In order to compare the performance of the optimized FOPID controller with other controllers، Genetic Algorithm (GA)، Particle swarm optimization (PSO)، Cuckoo Optimization Algorithm (COA) and Imperialist Competitive Algorithm (ICA).

In this paper، wavelet packet entropy is proposed for speaker-independent emotion detection from speech. After pre-processing، wavelet packet decomposition using wavelet type db3 at level 4 is calculated and Shannon entropy in its nodes is calculated to be used as feature. In addition، prosodic features such as first four formants، jitter or pitch deviation amplitude، and shimmer or energy variation amplitude besides MFCC features are applied to complete the feature vector. Then، Support Vector Machine (SVM) is used to classify the vectors in multi-class (all emotions) or two-class (each emotion versus normal state) format. 46 different utterances of a single sentence from Berlin Emotional Speech Dataset are selected. These are uttered by 10 speakers in sadness، happiness، fear، boredom، anger، and normal emotional state. Experimental results show that proposed features can improve emotional state detection accuracy in multi-class situation. Furthermore، adding to other features wavelet entropy coefficients increase the accuracy of two-class detection for anger، fear، and happiness.

Electromagnetic compatibility in switching power converters which are noise sources themselves، has a special importance. Electromagnetic interference (EMI) in the form of conducted or radiated reaches to sensitive sections and interferes with their operation. On the other، electromagnetic compatibility (EMC) standards causes another forces to reduce noise in switching converters. Major part of noise is due to the common-mode (CM) current passes through parasitic elements to the circuit ground (Earth). One of the important parasitic elements from the CM noise viewpoint is the switch heat-sink capacitor (common-mode capacitor). In this paper، a cancellation method of the heat-sink capacitor via a passive circuit is proposed in a 50W isolated flyback converter and is also modeled in OrCAD software. Also، experimental measurement results of the CM electromagnetic interference in regular and proposed flyback converter prototypes are presented to examine the modeling accuracy. Based on the experimental results، significant reduction of CM-EMI is verified after applying the cancellation method of the heat-sink capacitor.