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Articles 31 - 60 of 100
Full-Text Articles in Physical Sciences and Mathematics
A Procedure To Specify The Weighting Matrices For An Optimal Load-Frequency Controller, Silvio José Pinto Simões Mariano, Jose Álvaro Nunes Pombo, Maria Do Rosário Alves Calado, Luis António Fialho Marcelino Ferreira
A Procedure To Specify The Weighting Matrices For An Optimal Load-Frequency Controller, Silvio José Pinto Simões Mariano, Jose Álvaro Nunes Pombo, Maria Do Rosário Alves Calado, Luis António Fialho Marcelino Ferreira
Turkish Journal of Electrical Engineering and Computer Sciences
The linear quadratic optimal regulator is one of the most powerful techniques for designing multivariable control systems. The performance of the system is specified in terms of a cost, which is the integral of a weighted quadratic function of the system state and control inputs, that is to be minimized by the optimal controller. The components of the state cost weighting matrix, Q, and the control cost weighting matrix, R, are ours to choose in mathematically specifying the way we wish the system to perform. Changing these matrices, we can modify the transient behavior of the closed-loop system. This paper …
Design, Implementation, And Performance Analysis Of The Worldfip/Atm Local Bridge, Tuncay Aydoğan, İbrahi̇m Özçeli̇k, Aki̇f Kutlu, Hüseyi̇n Eki̇z
Design, Implementation, And Performance Analysis Of The Worldfip/Atm Local Bridge, Tuncay Aydoğan, İbrahi̇m Özçeli̇k, Aki̇f Kutlu, Hüseyi̇n Eki̇z
Turkish Journal of Electrical Engineering and Computer Sciences
World factory instrumentation protocol (WorldFIP) is a fieldbus network protocol that provides a link between level zero (sensors/actuators) and level one (field controllers such as programmable logic controllers, etc.) in industrial automation systems. Accessing and connecting the WorldFIP remotely is important for monitoring, maintaining, and controlling devices in a factory in which asynchronous transfer mode (ATM) is used as a backbone network. In this study, a transparent WorldFIP/ATM bridge was designed and implemented in order to access devices on WorldFIP via an ATM network. This designed bridge may also provide control of the devices over wide area networks. The bridge's …
A Novel Three-Phase Transformer Hysteresis Model In Matlab^{Tm} Simulink, Okan Özgönenel, Kami̇l Ri̇fat İrfan Güney, Ömer Usta, Hasan Di̇ri̇k
A Novel Three-Phase Transformer Hysteresis Model In Matlab^{Tm} Simulink, Okan Özgönenel, Kami̇l Ri̇fat İrfan Güney, Ömer Usta, Hasan Di̇ri̇k
Turkish Journal of Electrical Engineering and Computer Sciences
This paper presents a new transformer model displaying hysteresis using the MATLAB{\texttrademark} Simulink environment. The proposed model displays a complete scheme for the simulation of 3-phase transformers. The new model is mainly based on the transmission line model and the Jiles-Atherton model of a power system using lumped parameters. Jiles-Atherton model parameters were determined by curve fitting and numerical optimization iteration. The developed model is particularly suitable for fault analysis and protective relaying studies under harmonic conditions where the transformer is driven into the nonlinear regime. The performance of the method was evaluated by both theorical and experimental data.
Voltage- And Current-Controlled High Cmrr Instrumentation Amplifier Using Cmos Current Conveyors, Hamdi̇ Ercan, Sezai̇ Alper Teki̇n, Mustafa Alçi
Voltage- And Current-Controlled High Cmrr Instrumentation Amplifier Using Cmos Current Conveyors, Hamdi̇ Ercan, Sezai̇ Alper Teki̇n, Mustafa Alçi
Turkish Journal of Electrical Engineering and Computer Sciences
A new approach to the design of an instrumentation amplifier using only 2 CMOS current-controlled conveyors and an active resistor is introduced. The new approach, which has no passive components, offers a wide bandwidth and a high common-mode rejection ratio (CMRR). Electronically controllable gain by voltage and current is also obtained by this new circuit. The circuit is simulated using the parameters of a 0.35-\mu m TSMC CMOS technology. Theoretical analysis of the circuits was carried out, and the performance of the block circuit was confirmed through PSpice simulation results.
Trellis-Based Optimization Of Layer Extraction For Rate Adaptation In Real-Time Scalable Stereo Video Coding, Nükhet Özbek
Trellis-Based Optimization Of Layer Extraction For Rate Adaptation In Real-Time Scalable Stereo Video Coding, Nükhet Özbek
Turkish Journal of Electrical Engineering and Computer Sciences
The concept of quality layers (QLs) has been adopted in the scalable video coding standard to enable optimal rate adaptation of precoded video in the rate-distortion sense. QLs were previously extended to stereo and multiple-view scalable video for efficient transport of 3DTV over the Internet. However, it is not possible to use the QL method in applications that require real-time encoding since the priority determination process assumes the availability of the whole video sequence. In this work, a trellis-based online rate adaptation is proposed for real-time scalable stereo video coding, with a delay of 1 group of pictures (GoP). The …
Improved Square Properties Of Idea, Mete Akgün, Hüseyi̇n Demi̇rci̇, Mahmut Şami̇l Sağiroğlu, Pinar Kavak
Improved Square Properties Of Idea, Mete Akgün, Hüseyi̇n Demi̇rci̇, Mahmut Şami̇l Sağiroğlu, Pinar Kavak
Turkish Journal of Electrical Engineering and Computer Sciences
Block cipher encryption algorithms generally process on word structures of fixed length such as 8 or 16-bits. IDEA is one of the most widely used block ciphers and operates on 16-bit words. Square analysis is a method that exploits the word structure of block ciphers. Some square distinguishers of IDEA are given in previous studies. The best attacks against IDEA use square-like techniques. In this paper, we focus on the square properties of the IDEA block cipher. We consider all fixed word combinations of the plaintext to investigate the structural behavior of the algorithm. We observe that the cipher can …
Research On Cutoff Wavelength Of Dominant Mode And Field Patterns In Trapezoidal Microshield Lines, Hai Sun, Yujiang Wu
Research On Cutoff Wavelength Of Dominant Mode And Field Patterns In Trapezoidal Microshield Lines, Hai Sun, Yujiang Wu
Turkish Journal of Electrical Engineering and Computer Sciences
The influence of the position of the metallic signal strip on the cutoff characteristic of the dominant mode and the field patterns in 3 types of trapezoidal microshield lines are calculated by the edge-based finite element method. These trapezoidal microshield lines include trapezoidal microshield lines with a single signal line, dual signal lines, and 3 signal lines. The cutoff wavelength of the dominant mode can be adjusted by changing the dimensions of metallic signal strips as well as by adjusting their positions. Field patterns of the dominant mode and the first-higher-order mode for different dimensions and the dielectric constant of …
Fast Software Multiplication In F_2[X] For Embedded Processors, Serdar Süer Erdem
Fast Software Multiplication In F_2[X] For Embedded Processors, Serdar Süer Erdem
Turkish Journal of Electrical Engineering and Computer Sciences
We present a novel method for fast multiplication of polynomials over F_2 which can be implemented efficiently in embedded software. Fast polynomial multiplication methods are needed for the efficient implementation of some cryptographic and coding applications. The proposed method follows a strategy to reduce the memory accesses for input data and intermediate values during computation. This strategy speeds up the binary polynomial multiplication significantly on typical embedded processors with limited memory bandwidth. These multiplications are usually performed by the comb method or the Karatsuba-based methods in embedded software. The proposed method has speed and memory advantages over these methods on …
Study And Control Of 5-Level Pwm Rectifier-5-Level Npc Active Power Filter Cascade Using Feedback Control And Redundant Vectors, Thameur Abdelkrim, El Madjid Berkouk, Karima Benamrane, Tarak Benslimane
Study And Control Of 5-Level Pwm Rectifier-5-Level Npc Active Power Filter Cascade Using Feedback Control And Redundant Vectors, Thameur Abdelkrim, El Madjid Berkouk, Karima Benamrane, Tarak Benslimane
Turkish Journal of Electrical Engineering and Computer Sciences
The purpose of this paper is to develop a control and regulation method for the input DC voltages of a 5-level neutral point clamping (NPC) active power filter (APF). This APF is applied for the enhancement of medium-voltage network power quality by compensation of harmonic currents produced by an induction motor speed variator. In the first part, the authors present a topology of a 5-level NPC voltage source inverter and its simplified space vector pulse width modulation (SVPWM) control strategy. In the second part, the control strategy of the 5-level pulse width modulation current rectifier is presented. In the third …
Circuit Model And Parasitic Parameter Extraction Of The Spark Plug In The Ignition System, Quandi Wang, Yali Zheng, Jihui Yu, Jin Jia
Circuit Model And Parasitic Parameter Extraction Of The Spark Plug In The Ignition System, Quandi Wang, Yali Zheng, Jihui Yu, Jin Jia
Turkish Journal of Electrical Engineering and Computer Sciences
This paper presents a circuit model of the spark plug in the ignition system for conducted electromagnetic interference (EMI). Based on the spark plug's current discharge channel, the circuit model of the spark plug is established with the parasitic parameters and the air-gap model. The parasitic parameters of the spark plug are extracted with the finite element method, and the air-gap model of the spark plug is analyzed using the electric circuit principles and the air-discharge theory. The simulation and measurement results validate this model. Furthermore, this model confirms that the spark plug discharge is the main conducted EMI source …
Noncausal Forward/Backward Two-Pass Iir Digital Filters In Real Time, Adnane Mouffak, Belbachir Mohamed Faouzi
Noncausal Forward/Backward Two-Pass Iir Digital Filters In Real Time, Adnane Mouffak, Belbachir Mohamed Faouzi
Turkish Journal of Electrical Engineering and Computer Sciences
A novel method for implementing noncausal forward/backward 2-pass recursive digital filters in real time is presented. It is based on a segment-wise block processing scheme without overlapping. Factors that degrade the linearity of the overall system's transfer function are discussed. An analytical condition that corrects the system's linearity is elaborated upon using the state variable approach. A recursive algorithm is developed to compute an implementable condition for real-time filtering. A single first in, first out queue memory is introduced to ensure an organized and continuous data stream into the proposed system. This technique allows real-time, sample-by-sample filtering, and it yields …
Packet Traffic Features Of Ipv6 And Ipv4 Protocol Traffic, Cebrai̇l Çi̇fli̇kli̇, Ali̇ Gezer, Abdullah Tuncay Özşahi̇n
Packet Traffic Features Of Ipv6 And Ipv4 Protocol Traffic, Cebrai̇l Çi̇fli̇kli̇, Ali̇ Gezer, Abdullah Tuncay Özşahi̇n
Turkish Journal of Electrical Engineering and Computer Sciences
Nowadays, the IPv6 protocol is in a transition phase in operational networks. The ratio of its traffic volume is increasing day by day. The many provided facilities for IPv6 connection increasethe total IPv6 traffic load. IPv6-over-IPv4 tunnels, pilot programsto provide IPv6 connections, IPv6/IPv4 dual stack operating systems,and free IPv6 tunnel brokers cause the IPv6 protocol to expand quickly. For efficient resource utilization, the characteristics of network traffic should be determined accurately. Many traffic characterization studies regarding IPv4 have demonstrated that most of the network traffic is self-similar. Self-similarity causes significant impacts on network performance. With the increasing volume of IPv6 …
Adaptive Qos Scheduling In A Service-Oriented Grid Environment, Tan Fong Ang, Teck Chaw Ling, Keat Keong Phang
Adaptive Qos Scheduling In A Service-Oriented Grid Environment, Tan Fong Ang, Teck Chaw Ling, Keat Keong Phang
Turkish Journal of Electrical Engineering and Computer Sciences
The use of grid technology and web services for resource sharing has received tremendous attention in recent years. The merging of these 2 technologies is able to provide additional multiple types of services and functionalities. However, the problem of scheduling services to meet quality of service (QoS) requirements remains challenging. This paper proposes an adaptive QoS (AQoS) scheduling algorithm for service-oriented grid environments. AQoS uses benchmarking and curve-fitting based on historical records to estimate job length. Job length and users' QoS requirements are then used to make scheduling decisions. AQoS is able to maximize service availability, reliability, and resource utilization …
Reduction Of Torque Ripple In Dtc For Induction Motor Using Input-Output Feedback Linearization, Sebti Belkacem, Farid Naceri, Rachid Abdessemed
Reduction Of Torque Ripple In Dtc For Induction Motor Using Input-Output Feedback Linearization, Sebti Belkacem, Farid Naceri, Rachid Abdessemed
Turkish Journal of Electrical Engineering and Computer Sciences
Direct torque control (DTC) is known to produce fast responses and robust control in AC adjustable-speed drives. However, in the steady-state operation, notable torque, flux, and current pulsations occur. In this paper, nonlinear DTC of induction motor drives is presented based on a space vector pulse-width modulation scheme combined with the input-output feedback linearization technique. The variation of stator and rotor resistance due to changes in temperature or frequency deteriorates the performance of the DTC controller by introducing errors in the estimated flux linkage and the electromagnetic torque. This approach will not be suitable for high power drives such as …
Hybrid Feature Selection For Text Classification, Serkan Günal
Hybrid Feature Selection For Text Classification, Serkan Günal
Turkish Journal of Electrical Engineering and Computer Sciences
Feature selection is vital in the field of pattern classification due to accuracy and processing time considerations. The selection of proper features is of greater importance when the initial feature set is considerably large. Text classification is a typical example of this situation, where the size of the initial feature set may reach to hundreds or even thousands. There are numerous research studies in the literature offering different feature selection strategies for text classification, mostly focused on filters. In spite of the extensive number of these studies, there is no significant work investigating the efficacy of a combination of features, …
Optimization Of Pilot Tones Using Differential Evolution Algorithm In Mimo-Ofdm Systems, Muhammet Nuri̇ Seyman, Necmi̇ Taşpinar
Optimization Of Pilot Tones Using Differential Evolution Algorithm In Mimo-Ofdm Systems, Muhammet Nuri̇ Seyman, Necmi̇ Taşpinar
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, we propose a differential evolution (DE) algorithm for optimizing the placement and power of the pilot tones that are utilized by a least square (LS) algorithm for channel estimation in multiple-input and multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems. Computer simulations demonstrated that the performance of the LS algorithm was increased by optimizing the pilot tones with the DE algorithm instead of locating them orthogonally. We used the upper bound of the mean square error (MSE) as a fitness function of the DE algorithm for optimization tasks. With the use of an upper bound, it is not necessary …
Action-Reaction Based Parameters Identification And States Estimation Of Flexible Systems, Islam Shoukry, Emrah Deni̇z Kunt, Asif Sabanovic
Action-Reaction Based Parameters Identification And States Estimation Of Flexible Systems, Islam Shoukry, Emrah Deni̇z Kunt, Asif Sabanovic
Turkish Journal of Electrical Engineering and Computer Sciences
This work attempts to identify and estimate flexible system's parameters and states by a simple utilization of the Action-Reaction law of dynamical systems. Attached actuator to a dynamical system or environmental interaction imposes an action that is instantaneously followed by a dynamical system reaction. The dynamical system's reaction carries full information about the dynamical system including system parameters, dynamics and externally applied forces that arise due to system interaction with the environment. This in turn implies that the dynamical system's reaction can be considered as a natural feedback as it carries full coupled information about the dynamical system. The idea …
Tunable Srr-Based Substrate For A Microstrip Patch Antenna, Adnan Sondaş, Mustafa Hi̇kmet Bi̇lgehan Uçar, Yunus Emre Erdemli̇
Tunable Srr-Based Substrate For A Microstrip Patch Antenna, Adnan Sondaş, Mustafa Hi̇kmet Bi̇lgehan Uçar, Yunus Emre Erdemli̇
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, a microstrip patch antenna over an artificial substrate composed of split-ring resonator (SRR) elements is introduced. As the SRR-based substrate provides miniaturization for the patch, metallic loadings placed between the rings of the SRR elements offer frequency-tuning capability. Practical switch models are employed in lieu of those loadings to demonstrate dynamic control of the operational frequency. The full-wave analysis and design of the proposed tunable patch were carried out using CST Microwave Studio, and the cross-comparisons were provided via Ansoft HFSS. Preliminary measurements are also presented, demonstrating the prospective performance of the proposed design.
Short-Term Nodal Congestion Price Forecasting In A Large-Scale Power Market Using Ann With Genetic Optimization Training, Majid Moazzami, Rahmat Allah Hooshmand
Short-Term Nodal Congestion Price Forecasting In A Large-Scale Power Market Using Ann With Genetic Optimization Training, Majid Moazzami, Rahmat Allah Hooshmand
Turkish Journal of Electrical Engineering and Computer Sciences
In a daily power market, price and load forecasting are the most important signals for the market participants. In this paper, an accurate feed-forward neural network model with a genetic optimization Levenberg-Marquardt back propagation training algorithm is employed for short-term nodal congestion price forecasting in different zones of a large-scale power market. The use of genetic algorithms for neural network training optimization has a remarkable effect on the accuracy of price forecasting in a large-scale power market. The necessary data for neural network training are obtained by solving optimal power flow equations that take into account all effective constraints at …
Skewed Alpha-Stable Distributions For Modeling And Classification Of Musical Instruments, Mehmet Erdal Özbek, Mehmet Emre Çek, Feri̇t Acar Savaci
Skewed Alpha-Stable Distributions For Modeling And Classification Of Musical Instruments, Mehmet Erdal Özbek, Mehmet Emre Çek, Feri̇t Acar Savaci
Turkish Journal of Electrical Engineering and Computer Sciences
Music information retrieval and particularly musical instrument classification has become a very popular research area for the last few decades. Although in the literature many feature sets have been proposed to represent the musical instrument sounds, there is still need to find a superior feature set to achieve better classification performance. In this paper, we propose to use the parameters of skewed alpha-stable distribution of sub-band wavelet coefficients of musical sounds as features and show the effectiveness of this new feature set for musical instrument classification. We compare the classification performance with the features constructed from the parameters of generalized …
Analysis Of Orthogonal Matching Pursuit Based Subsurface Imaging For Compressive Ground Penetrating Radars, Mehmet Ali̇ Çağri Tuncer, Ali̇ Cafer Gürbüz
Analysis Of Orthogonal Matching Pursuit Based Subsurface Imaging For Compressive Ground Penetrating Radars, Mehmet Ali̇ Çağri Tuncer, Ali̇ Cafer Gürbüz
Turkish Journal of Electrical Engineering and Computer Sciences
It is shown that compressive sensing (CS) theory can be used for subsurface imaging in stepped frequency ground penetrating radars (GPR), resulting in robust sparse images, using fewer measurements. Although the data acquisition time is decreased by CS, the computational complexity of the minimization based imaging algorithm is too costly, which makes the algorithm useless, especially for extensive discretization or 3D imaging. In this paper, a greedy alternative, orthogonal matching pursuit (OMP) is used for imaging subsurface and its performance under various conditions is compared to CS imaging method. Results show that OMP could reconstruct sparse signals robustly as well …
A Novel Structure To Enhance Magnetic Force And Velocity In Tubular Linear Reluctance Motor, Ali Mosallanejad, Abbas Shoulaie
A Novel Structure To Enhance Magnetic Force And Velocity In Tubular Linear Reluctance Motor, Ali Mosallanejad, Abbas Shoulaie
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, a novel design for a tubular linear reluctance motor (TLRM) has been developed. This paper presents a novel structure to enhance magnetic force and velocity in a TLRM. The new structure is accomplished through some changes in a TLRM, which results in a step winding structure. Comparing the proposed motor and the typical motor performances, it is proven that the proposed motor has better performance. For dynamic modeling of the proposed TLRM and to obtain the motor output characteristics, the method used for inductance profile calculation is described. The performance improvements in the proposed motor are evaluated …
Fractional Pid Controllers Tuned By Evolutionary Algorithms For Robot Trajectory Control, Zafer Bi̇ngül, Oğuzhan Karahan
Fractional Pid Controllers Tuned By Evolutionary Algorithms For Robot Trajectory Control, Zafer Bi̇ngül, Oğuzhan Karahan
Turkish Journal of Electrical Engineering and Computer Sciences
The aim of this paper is to compare the performances of a fractional order proportional integral derivative (FOPID) controller tuned with evolutionary algorithms for robot trajectory control. In order to make this comparison, a 2-degrees-of-freedom planar robot was controlled by a FOPID controller tuned with particle swarm optimization (PSO) and a real coded genetic algorithm (GA). In order to see the effects of the cost functions on the optimum parameters of the FOPID controller, 3 different cost functions were used: the root mean squared error (MRSE), mean absolute error (MAE), and mean minimum fuel and absolute error (MMFAE). In order …
Improved Computerized Evaluation Of Abdominal Aortic Aneurysm, Semi̇h Utku, Hulusi̇ Baysal, Reyat Yilmaz, Aytaç Gülcü, Recep Alp Kut, Ahmet Yi̇ği̇t Göktay
Improved Computerized Evaluation Of Abdominal Aortic Aneurysm, Semi̇h Utku, Hulusi̇ Baysal, Reyat Yilmaz, Aytaç Gülcü, Recep Alp Kut, Ahmet Yi̇ği̇t Göktay
Turkish Journal of Electrical Engineering and Computer Sciences
Accurate measurements of arterial anatomy are emerging as the most important determinants of endovascular abdominal aneurysm repair. It is quite difficult to define and measure arterial anatomy features quantitatively due to the complex structure of the aneurysm and insufficient visual feedback. During decision making, to assist operators in diagnosing abdominal aortic aneurysms, a specialized preprocessing Abdominal Aortic Aneurysm Measurement and Evaluation Tool (AMET) was developed. AMET provides visual interfaces with broad measurement capabilities to generate a 3D model of the aorta for a better diagnosis and accurate stent selection. The accuracy and usability of the tool was tested with a …
An Implementation Of Modified Scatter Search Algorithm To Transmission Expansion Planning, Majid Zeinaddini Maymand, Masoud Rashidinejad, Hamid Khorasani, Mohsen Rahmani, Amin Mahmoudabadi
An Implementation Of Modified Scatter Search Algorithm To Transmission Expansion Planning, Majid Zeinaddini Maymand, Masoud Rashidinejad, Hamid Khorasani, Mohsen Rahmani, Amin Mahmoudabadi
Turkish Journal of Electrical Engineering and Computer Sciences
Transmission network expansion planning (TNEP) is one of the most important tasks in the field of power systems, especially in deregulated power system environments. TNEP is a nonlinear mixed integer programming problem that can be solved via hybrid heuristic algorithms. This paper presents a modified scatter search algorithm (MSSA) to reinforce the ordinary scatter search algorithm (SSA) to be equipped for handling large scale transmission expansion planning (TEP) problems. The proposed methodology is based on the SSA, incorporating some improved strategies so as to decrease the number of linear programming problems required to be solved iteratively. In this study, it …
Energy Savings In Simultaneous Multi-Threaded Processors Through Dynamic Resizing Of Datapath Resources, Gürhan Küçük, Mi̇ne Mesta
Energy Savings In Simultaneous Multi-Threaded Processors Through Dynamic Resizing Of Datapath Resources, Gürhan Küçük, Mi̇ne Mesta
Turkish Journal of Electrical Engineering and Computer Sciences
Nowadays, all the designers of systems from high-performance servers to battery-operated handheld devices aim for reliability, high-performance and longevity. Central within these aims the issue of processor power consumption is becoming increasingly important. In this study, we aim to adapt our already-proven method for single-threaded superscalar processors to simultaneous multi-threaded (SMT) processors for energy savings. The original method focused on resizing datapath resources according to the demands of running applications. To achieve this, the targeted resources are physically divided into multiple partitions, and turned on and off according to the needs of the applications. Since, the energy consumption of the …
A New Multipath Channel Transformation Technique, Tuğrul Çavdar
A New Multipath Channel Transformation Technique, Tuğrul Çavdar
Turkish Journal of Electrical Engineering and Computer Sciences
A new channel transformation technique is introduced in this paper The technique is employed on the receiver side and has 2 filters. The first filter is the inverse complex conjugate of the estimated channel. The profile of this filter's output is triangular. The taps of the second filter are calculated according to the output of the first filter to produce an exponentially decreasing profile. This technique transforms most channel profiles to exponentially decreasing channel profiles. Thus equalizers adopting the proposed technique may have better bit error rates and lower computational complexity on frequency-selective channels. This paper evaluates the efficiency of …
Voltage Stability Via Energy Function Analysis On Reduced Order Model Of Power System, Ahmet Çi̇fci̇, Yilmaz Uyaroğlu, Mehmet Ali̇ Yalçin
Voltage Stability Via Energy Function Analysis On Reduced Order Model Of Power System, Ahmet Çi̇fci̇, Yilmaz Uyaroğlu, Mehmet Ali̇ Yalçin
Turkish Journal of Electrical Engineering and Computer Sciences
A power system is a typical nonlinear dynamical system and voltage stability is an important subject of power system stability. This paper describes the use of the variable gradient method in a reduced order model of a single-machine infinite-bus power system. Additionally, the system's Lyapunov (energy) function is created and thus the system's energy level changes' effects on the system's stability are shown using the MACSYMA program. The Lyapunov function allows the determination of stability for nonlinear systems without the need to find exact solutions.
A Novel Approach For Optimal Allocation Of Distributed Generations Based On Static Voltage Stability Margin, Mohsen Rezaie Estabragh, Mohsen Mohammadian, Mehdi Shafiee
A Novel Approach For Optimal Allocation Of Distributed Generations Based On Static Voltage Stability Margin, Mohsen Rezaie Estabragh, Mohsen Mohammadian, Mehdi Shafiee
Turkish Journal of Electrical Engineering and Computer Sciences
This paper presents a newly developed approach to find the optimal location of distributed generations (DGs) to improve power system voltage stability margin and reduce losses incorporating the constraints. The loadability limit index is used to assess the static voltage stability security margin, which is associated with the point of voltage collapse limit. Based on this, a toolbox is developed to recognize the loadability margin in power networks. Finally, the mentioned problem is modeled as a nonlinear and multiobjective optimization problem. The proposed method establishes a tradeoff between the security index and power losses in DG placement using the hybrid …
Reconfigurable Antenna Structure For Rfid System Applications Using Varactor-Loading Technique, Yusuf Sevi̇nç, Adnan Kaya
Reconfigurable Antenna Structure For Rfid System Applications Using Varactor-Loading Technique, Yusuf Sevi̇nç, Adnan Kaya
Turkish Journal of Electrical Engineering and Computer Sciences
A novel method is presented for electrically tuning the frequency of a compact radio-frequency identification (RFID) tag antenna. A tuning circuit, comprising a radio frequency (RF) switch and discrete passive components, was completely integrated into the antenna element, which is thus free of DC wires. The low-profile printed antennas were fabricated together with the layouts of the DC control circuits and other RF/baseband circuit footprints. A surface-mounted varactor was applied as a frequency-tuning element at the proper places of the meandered slots in the compact antenna. Prototype designs showed that the in-band frequency (return loss < 10 dB) was tunable from 2.4 GHz to 2.8 GHz when the bias voltage varied from 4 V to 7 V. The impact of the tuning circuit on the antenna's return loss and radiation pattern were experimentally studied through comparison with the performance of a reference antenna not incorporating the tuning circuit. The proposed frequency tuning concept can be extended to more complex compact structures as well as other types of antennas to give enhanced electrical performance.