JOURNAL OF FACULTY OF ENGINEERING (UNIVERSITY OF TABRIZ)
Year:2008 | Volume:35 | Issue:1 (49) ELECTRICAL ENGINEERING|Papers Count:7

This paper considers the details of design and implementation of a three-phase to three-phase matrix converter rated at an input voltage of 380V line and an output current of 7A. The designed converter is a generalized converter and can be safely operates with maximum three inputs and three outputs regardless of the form of the input and output waveforms. In this paper, first the voltage and current ratings of power semiconductor devices are calculated for the prototype converter. Then, the gate drive circuit of the bi-directional switches is designed. Also, a voltage clamp circuit is used to protect the devices against severe over-voltages. A simple R-C snubber circuit has been used to limit the device voltage to an appropriate level. Also, the snubber circuit will be analyzed completely. Finally, the simulation results by PSC AD software and also the practical implementation results will be given.

In this paper a new and completely linear algorithm is proposed for robust control of flexible joint robots. Moreover, the robust stability of the closed loop system in the presence of structured and unstructured uncertainties is analyzed. In order to develop the controller, flexible joint robot with structured and unstructured uncertainties is modeled and converted into a singular perturbation form. A robust linear control algorithm is proposed for the slow dynamics and its robust stability conditions are derived using Thikhonov's theorem. Then, the robust stability of the total system considering the proposed composite controller is analyzed, and the sufficient conditions for robust stability of the overall system are determined. Finally the effectiveness of the proposed controller is verified through simulations. It is shown that not only the tracking performance of the proposed controller is very suitable, but also the actuator effort is much smaller than that in the previous result.

With the increasing importance of fused images that are acquired from various medical imaging systems, fast and automatic registration of images from disparate sources has become critical to the success of these endeavors. Resources show that the more; accurate algorithm, the more run time is needed. This study is experimented for some famous algorithms of registration for 2D MRI and PET brain images that obtained from the same cross section. The goal of this paper is to present a new integrated algorithm which reduces registration process complexity while maintaining high accuracy. This algorithm is based on combining the intensity and geometric features and using both features together. Comparison of results shows high accuracy and low run time in comparison with the other methods.

Using a detailed model of wind power station, including wind turbine, wind turbine governor, wind resources and the DFIG, the performance of wind power station is investigated. It consists of wound rotor induction machine, grid side converter, rotor side converter and associated controllers. The control scheme uses stator flux oriented control for the rotor side converter and grid voltage vector control for the grid side converter. PSCAD/EMTDC is used for simulation. The main power electronic circuits and controllers are also developed in details and in the same simulation tool. The simulation model is also used to investigate the performance of controllers under different network conditions. The responses of rotor speed, active power output and blade pitch angle are obtained for various conditions of power grid. While this study shows the performance of a wind power station in variable wind and power grid conditions, it is an essential and preliminary part of investigating the integrating issues of renewable distributed generation with power grid.

Increase of inductance gradient is one of the most common methods to increase applied force to projectile. Increase of inductance gradient is reachable by using augmented rails. In the first section of this paper, after definition of problem and electromagnetic equations, effect of variation of rails dimension and distance between rails on inductance gradient, self inductance and mutual inductance for circular and rectangular rails are explored. In the second part, a new method for increase of inductance gradient in simple railgun and augmented railgun is suggested. This method uses technique that decreases reluctance of flux path and makes a noticeable increase in the gradient inductance.[1]

IGBT's are widely used in switching power conversion applications due to their distinctive advantages such as easiness in drive and high frequency switching capability. Since IGBT's can handle higher voltage and power with higher power density and lower cost compared to MOSFET's, they are replacing MOSFET's in high power applications. Because of tailing current characteristic of IGBT its operating frequency is limited. To operate IGBT at higher switching frequency, it is required to reduce the turn-off switching loss. For this purpose, ZVZCS techniques are introduced. In these techniques which uses phase-shift control for driving the switches, ZVS condition is provided for leading-leg switches by adding external capacitor and ZCS is achieved for lagging-leg switches by resetting the primary current during the freewheeling period. In high power applications, paralleled dc-dc converters is often preferable to a single-converter considering modularity, performance, reliability, availability, redundancy, size reduction and thermal management. When operating converter modules are in parallel, the major concern is equal load sharing among the paralleled modules. In this paper a 3 kw, 350 v, 30 khz FB-PWM-ZVZCS power supply is implemented. By adding an auxiliary inductance and change in control strategy the ZVS range of leading leg switches is extended. Then load sharing methods are introduced briefly. Finally three module of implemented power supply is paralleled using automatic Master slave load sharing method and a 9 kw power supply is realized.

Conventional high-frequency half-bridge inverters are used widely in industrial and domestic utilizations due to their simplicity and controllability. The output power of these inverters, especially in PWM control technique, will be limited to a narrow range if soft-switching attributes such as zero voltage and zero current switching (ZVZCS) are used. In order to solve this problem this paper proposes a new soft-switching high-frequency half bridge inverter, which employs an active quasi-resonant snubber. This inverter, which is controlled by fixed frequency PWM control technique can regulate output power continuously and is designed according to the principals of conventional high-frequency half-bridge inverters. The soft-switching operation condition of the proposed inverter is expanded to wider range than conventional one. Fixed-frequency, 20 kHz, high thermal efficiency induction-heating cookers are some of the potential applications of this new topology which can be used in domestic and industrial applications. Experimental results illustrate the proof of both the verification of simulation results and the feasibility features of the proposed inverter.