مهندسی برق مجلسی
سال:1387 | دوره:2 | شماره:1 |تعداد مقالات:20

In this paper, a grid connected PV system acting as shunt active power filter for power quality enhancement is presented. Further, a DC-DC boost converter is used to interface the photovoltaic generator with the grid, which provides a continuous power flow from the PV generator into the grid through a Voltage Source Inverter (VSI). Hence, a nonlinear backstepping control method with predictive direct power control for the shunt active power filter side is presented, and a suitable backstepping DC-DC boost converter is also developed, with a view to reduce harmonic currents and insuring reactive power compensation under nonlinear loads variations on the utility grid, and also extracts the maximum amount of power from the photovoltaic generator. Processor in the Loop (PIL) co-simulation results prove the performances efficiency of the implemented control algorithms under a nonlinear load operating condition.

Biological components including cells, proteins, and nucleic acids have been studied by using biological sensors. All compounds in the organisms have sensors with identical mechanical sensors. Most of these sensors are specific cells which are sensitive to physical characteristics of outside environment including light, motion, temperature, magneticfield, gravity, moisture, vibration, pressure, electrical fields, and sound. Since biosensors could be fabricated by using photonic crystals, these structures are used in designing the sensor due to the unique characteristics of photonic crystals. Refractive index around the sensing hole was changed and output transmission spectrum was studied. By changing refractive index, transmission spectrum undergoes measurable change and biomolecule could be measured by sensor in mentioned conditions. Results have shown that this sensor has good sensitivity for measuring small dimensions. In addition, high speed, high quality, simple structure, as well as higher sensitivity are other characteristics of photonic crystal sensors compared to other sensors.

In this paper, the structure of a 16-by-16 unsigned hybrid (serial-parallel) multiplier has been proposed. Parallel multipliers, in comparison with serial multipliers, have higher speed and higher power consumption. In hybrid structures, to reduce power and increase speed, both serial and parallel techniques are used. The proposed structure improves propagation delay and reduces power consumption using pipeline and retime techniques. Simulation results show that it has 5. 7 ns propagation delay and 2. 65 mW power consumption. The figure of merit for energy consumption is 15. 2 PJ. The proposed multiplier has been designed using 0. 18 μ m TSMC process at 1. 8 V supply and simulated using Cadence tools. The layout of the multiplier occupies 52414 μ m 2.

This paper proposes a H∞ Fuzzy robust controller for Doubly Fed Induction Generator (DFIG) based wind turbines. The power exchange between the machine stator and the grid is carried out by acting on the rotor via a bidirectional converter. The control objective is to regulate the stator active and reactive power generated from the DFIG by means of two kinds of controllers named H∞ PI and H∞ Fuzzy. Comparison study between the proposed controllers considering reference tracking and robustness to parameter variations is discussed. Simulation results illustrate the effectiveness of the H∞ Fuzzy controller compared with the other one for time-varying reference tracking and parameters variations, which improves quality and quantity of generated power.

In this paper, dual-hops and multi-hops cognitive radio Ad Hoc networks has been considered. It is vital mentioning that the primary user interference effect on the secondary user has also been considered. The design of the problem is to achieve an optimal solution for channel allocation and power in dual and multi hop in Cognitive Radio Ad Hoc Networks (CRNs). The main goal is to minimize the outage probability and increasing the length of your network life time, while simultaneously observing the transmission power constraints and the threshold of interference with the primary user. This problem was solved using the standard technique of solving convex optimization problem and weighted bipartite matching. All of the analysis is for both DF, and amplifying and transmission AF protocols. Comparison and measurement of the systems performance is outage probability. Simulation results have shown that the proposed scheme not only minimizes the outage probability compared to existing ones, but also reduces PU interference and saves overall transmission efficiency by Secondary Users.

he considerable development of the electricity market subjects in recent years has provided a complex and more competitive environment for the participants. Each participant in this environment adopts a special strategy to maximize its profit or minimize its energy costs considering the significant constraints. In this paper, a short term optimal scheduling of thermal units, hydropower units, wind turbines, and pumped storage units has been proposed based on the energy market guidelines. The main objective of this research is to minimize the thermal energy production costs considering the uncertainty parameters along with the maximum utilization of clean energy production in the system. In order to evaluate the research goals, IEEE 5-bus standard test system is selected as the case study, which is equipped with both conventional and clean energy resources. In addition, probabilistic behaviors related to energy demand and wind production have been considered. Results proved the effectiveness of this model in minimizing the energy cost of thermal units.

In this work, Ultra Wide-Band (UWB) microwave filters are designed and fabricated using a rectangular ring resonator. The UWB microwave filters work in the 3. 1GHz to 10. 6GHz frequency band, which is designed to coverage the FCC frequency spectrum for UWB systems. These filters, in addition to being ultra-wideband, are designed to prevent interference in some frequency bands, such as WiMAX band (3. 5GHz), WLAN band (5. 2-5. 8GHz) and satellite communication systems (8GHz) band. For this reason, in designing these filters intelligently, it is necessary to take precautions to ensure producing narrow and precise notches in the frequency response to prevent interference. This broad bandwidth and narrow notches with adjusted even or odd mode resonator frequencies, can be controlled by varying the characteristic impedance of the rectangular ring resonator. The proposed structures are simulated and optimized using HFSS software, so that the results of fabrication and measurement of these filters have an excellent agreement with the simulation results.

This article describes a workflow executed with MATLAB simulation and practical measurements for single phase power transformer. In addition, no-load, short-circuit test and load test are achieved in this work. The test procedures are implemented on a real transformer (terco– type) which has specifications of (1KVA, 220/110V, 50Hz). Finally, the simulation results are appeared proximately similar from the practical results.

This paper is concerned with a controller design method for Networked Control Systems (NCSs) with time-varying random delays. The proposed controller is an event-based controller and is able to effectively save the network bandwidth and energy resources of the system in comparison with common control schemes while guaranteeing the stability of the system. The proposed controller switches between two main triggering schemes: event-triggered control scheme and self-triggered control scheme. The stability issue in this combinatorial method is also considered. The validity of the proposed algorithm is confirmed via simulation results and the results are well compared with results from exerting event-triggered and self-triggered control individually.

Distributed Generation (DG) is a common technology in today’ s distribution networks due to its exclusive benefits. However, DG units introduce a series of new issues to distribution network beside their benefits. Adding a DG unit to the network can change the direction and magnitude of the power flow and fault currents through branches. It may cause the failure of the original protection system or false tripping of some existing relays. In this paper, a new adaptive approach is introduced for classification of different DG topologies in distribution network using the existing setting groups in over current relays. This method determines those settings such that maximum number of the possible scenarios for different operations in distribution system are covered including grid-connected mode, autonomous mode, and DGs capacity changes. In order to verify the performance of the new method, two simulation studies are performed on 14-node and IEEE 33-node distribution network test systems. DIgSILENT software has been employed to simulate the network in various operational modes.

Identification systems based on biometrics have been conventional more than traditional identification systems in the last two decades. Many biometrics have been provided such as fingerprint, palm, iris, the vein of palm and veins of fingerprint and such. One of the challenges discussed in biometrics is physical damages. The biometric of fingers knuckles is one of the biometrics less exposed to the physical damages. Several methods have been suggested for identification with various weak points such as high mathematical complications and a very low rate of identification. The present study suggests a new method for identification which is based on Zernike Moment. Zernike moment extracts the features of the picture several times. What distinguishes this algorithm from its counterparts is that it has got high accuracy in demarcating similar pictures of different classifications. In addition to its logical calculating complications, this method was able to record a very appropriate rate of identification facing some challenges such as noise, rotation, and transition.