JOURNAL OF FACULTY OF ENGINEERING (UNIVERSITY OF TABRIZ)
Year:2004 | Volume:30 | Issue:1 (34) Electronics|Papers Count:8

This paper presents the results of design, simulation and implementation of static V AR compensator (STATCOM). The power circuit of this STATCOM consists of a three-phase voltage source inverter with IGBT switches. The control circuit is based on using instantaneous reactive power theory (pq theory) and the programming language is C. The simulation and experimental results show acceptable operation of STATCOM in compensation for instantaneous reactive power and achieving unity power factor in utility side.

Variety of methods for traffic policing such as windowing algorithm and leaky bucket for computer networks have been proposed in the literatures. The windowing algorithm works well for packet networks but it is not appropriate for High speed networks such as ATM. In this paper, a new group of traffic policers for ATM network has been proposed. These proposed traffic policers are obtained by improving the leaky bucket method. Learning automata is used to adapt the parameters of the leaky bucket according to the behavior of the traffic sources. To study the effectiveness of the proposed methods, computer simulations have been conducted. The results of simulation have shown that the proposed methods reduce the percentage of the cell loss. The proposed traffic policer works well for the situations where the traffic characteristics. Of the source are unknown.

Switched reluctance motor (SRM) has been the subject of many investigations in recent years. The SR technology is a feasible and economically advantageous option for future electromotor production in Iran. However, computational intensive analysis methods (e.g. finite element (FE) analysis) and iterative search for optimal values of design parameters (e.g. genetic algorithms) can not be jointly carried out online. In this paper, we outline a three-stages design process for determination of the optimal electromotor specifications. In the first stage, FE analysis is used for computation of performance characteristics associated with various design parameters. Next, an interpolator is trained to establish a mapping from design parameters to performance characteristics. Finally, the latter values are optimized via multicriteria genetic algorithm.

In the new industrial era where digital control systems have widely employed in most equipments, the car industry is of no exception and everyday advancement in different engine control is proposed by digital control systems. The quantity of "Air Fuel Ratio-A/F" is one of particular parameters to be handled digitally for exact optimization of engine control to provide maximum power and throttle, together with fuel consumption and reducing pollution, etc. as well as a result of burning petroleum. Classical controllers in response to inherent delays to transient engine conditions behave unreliable, thus in this research, to aim for exact quantity of A/F a modern algorithm with control structure is utilized. The gas aperture angular position and engines speed are A/F system control input and universal exhaust oxygen sensor (UEGO) response as system output. The gas aperture in this control is of drive-by-wire throttle kind to provide electronic control. With the employment of this aperture. a proportionally exact control over air flow dynamics is achieved. The bulk that calculates the fuel value in every cycle of the engine operation is called injection fuel and is dependent upon the operated pulse width that the injection fuel mass can be regulated. The engine speed is also measured by a turning plate together with the crank shall turning. Moreover. by design and construction of a hardware electronic board employing an 80C 196KB powerful microcontroller. the size of electronic system and thus the tolerance to system's noise is considerably reduced. The hardware results adequately matched those obtained by software.

In this paper, finite element method is used for simulation of a railgun and calculation of rails and armature forces. A magnetic field produced by applying a semi- pulse current to a railgun causes Lorenz forces in rails and armature. This latest force accelerates the armature and projectile. In this study, after determining this force, acceleration, velocity and positions of armature versus time are calculated. The maximum value of rails' force versus time in every rail points were calculated too. This value is very important in railgun and their material design and fabrication.

This paper presents a new optimal adaptive neuro - fuzyy power system stabilizer to damp out power system oscillations. In this design, five layers of neuro-fuzzy network are used. Fuzzy rules and inferences, input out put membership functions can be adjusted by learning with back propagation and hybrid algorithms. Finally, a comparison between proposed controller and others is carried out in one-machine and multi-machine power system.

The application of a newly developed algorithm is presented which allows the on-line Identification and tracking of the time-varying harmonic content of distorted voltage and current waveforms arising at the point of connection between HVAC and HVDC power systems. A novel discrete Kalman filtering technique is used which is able to acquire rapidly and track accurately the values of harmonic amplitudes and phases. The effectiveness of the presented method is demonstrated by a simple test case. Amplitude and phase acquisition is compared with that of an on-line FFT-based frequency scanner. The proposed algorithm has been applied in the identification and tracking of the harmonic content of waveforms obtained at the point of HVAC/HVDC common coupling.

Since the most faults on overhead high voltage transmission lines are transient single phase to ground faults, the successful operation of re-closing relays significantly influences stability and continuity of power systems. In order to set the dead time of usual re-closing relays or design adaptive re-closing relays, it is required to know the final extinction time of the secondary arc and variation manner of this time by different factors. Therefore, in this paper, a comprehensive investigation of various factors impact on the secondary arc extinction time is presented via simulation of various fault conditions on a test power system and analysis of the fault voltage components. For this purpose, the power system model and the non linear dynamic model of the secondary arc have been implemented in the used software. Using the studies results, the approximate sensitivity of the final extinction time of the secondary arc to related factors are presented in terms of number of power cycles.