Multilevel Hybrid Cascade-Stack Inverter With Substantial Reduction In Switches Number And Power Losses,
2015
TÜBİTAK
Multilevel Hybrid Cascade-Stack Inverter With Substantial Reduction In Switches Number And Power Losses, Mahdi Toopchi Khosroshahi, Ali Ajami, Ata Ollah Mokhberdoran, Mohammadreza Jannati Oskuee
Turkish Journal of Electrical Engineering and Computer Sciences
This paper proposes a multilevel hybrid cascade-stack (HCS) converter. Recently, different new topologies for cascade-type converters have been suggested with the goal of reducing switch number, loss, switch PIV, etc. Meanwhile, output voltage steps increase, and the number of switches is predominately reduced in the suggested inverter in comparison to conventional cascade converters. Additionally, a reduction in the number of on-state switches in the introduced topology causes power loss and voltage drop to decrease. Firstly, the fundamental parts of inverter configuration are described. Afterwards, symmetric and asymmetric converter types are discussed. Simulation and experimental results for 11- and 23-level symmetric …
A Fourth-Order Accurate Compact 2-D Fdfd Method For Waveguide Problems,
2015
TÜBİTAK
A Fourth-Order Accurate Compact 2-D Fdfd Method For Waveguide Problems, Lokman Kuzu
Turkish Journal of Electrical Engineering and Computer Sciences
In this work, a fourth-order accurate 2-D finite difference frequency domain method is proposed for the analysis of general waveguide structures. Finite difference techniques have been extensively used to solve electromagnetic problems over the decades. These methods discretize the computational domain using the Yee cell, but the standard Yee scheme used in these methods is only second-order accurate. In order to demonstrate the advantages of the proposed scheme compared to the multiresolution frequency domain method and the traditional 2-D finite difference frequency domain scheme, the dispersion characteristics of various waveguide structures are analyzed.
Calculation Of Surface Leakage Currents On High Voltage Insulators By Ant Colony Algorithm-Supported Fem,
2015
TÜBİTAK
Calculation Of Surface Leakage Currents On High Voltage Insulators By Ant Colony Algorithm-Supported Fem, Dursun Öztürk, Mehmet Cebeci̇
Turkish Journal of Electrical Engineering and Computer Sciences
The weakness of the outer insulation at high voltages is the reduction of the surface resistance as a result of the environmental pollution yielding formation of flashover due to the surface leakage currents. In this study, it was shown how to calculate the surface leakage currents resulting in flashover in polluted insulators and therefore power cuts by means of the ant colony algorithm (ACA). For this purpose, first, field distribution on the sample insulator surface in question was defined by the Laplace equation ($\nabla^{2}$V = 0). With the help of the finite element method (FEM), the Laplace equation was obtained …
Superior Decoupled Control Of Active And Reactive Power For Three-Phase Voltage Source Converters,
2015
TÜBİTAK
Superior Decoupled Control Of Active And Reactive Power For Three-Phase Voltage Source Converters, Hesam Rahbarimagham, Erfan Maali Amiri, Behrooz Vahidi, Gevorg Babamalek Gharehpetian, Mehrdad Abedi
Turkish Journal of Electrical Engineering and Computer Sciences
This paper presents an active-reactive power control strategy for voltage source converters (VSCs) based on derivation of the direct and quadrature components of the VSC output current. The proposed method utilizes a multivariable proportional-integral controller and provides almost completely decoupled control capability of the active and reactive power with almost full disturbance rejection due to step changes in the power exchanged between the VSC and the grid. It also imposes fast transient response and zero steady-state error as compared to the conventional power control approaches. The applicability of the proposed power control strategy for providing the robust stability of the …
A Real-Time Life-Care Monitoring Framework: Warnred Hardware And Software Design,
2015
TÜBİTAK
A Real-Time Life-Care Monitoring Framework: Warnred Hardware And Software Design, Gamze Doğali Çeti̇n, Özdemi̇r Çeti̇n, Cüneyt Bayilmiş
Turkish Journal of Electrical Engineering and Computer Sciences
It is shown by many statistical studies that the senior population, especially in developed countries, is in an increasing trend. For many reasons they tend to have in-home health care providers. The recent studies on biomedical information management focused on remote health monitoring frameworks including heart rate monitoring systems, glucose measurements for diabetics, and remote monitoring EEG and ECG. The main purposes of these studies are timely response to emergency situations and ensuring that the person is in a stable condition. In this study, developed via a system-on-chip circuit, we process the data collected from subjects through a temperature sensor …
Matching Named Entities With The Aid Of Wikipedia,
2015
TÜBİTAK
Matching Named Entities With The Aid Of Wikipedia, Abdullah Bawakid, Mourad Oussalah, Naveed Afzal, Seong Shim
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper we propose a novel framework using features extracted from Wikipedia for the task of matching named entities. We present how the employed features are extracted from Wikipedia and how its structure is utilized. We describe how a term-concepts table constructed from Wikipedia and the redirect links are integrated in the framework. In addition, the internal links within Wikipedia along with the categories structure are also used to compute the relatedness between concepts. We evaluate the built framework and report its performance in the applications of word sense disambiguation and named entities matching. The system performance is compared …
Effect Of Nonuniform Varying Delay On The Rate Of Convergence In Averaging-Based Consensus,
2015
TÜBİTAK
Effect Of Nonuniform Varying Delay On The Rate Of Convergence In Averaging-Based Consensus, Onur Ci̇han, Mehmet Akar
Turkish Journal of Electrical Engineering and Computer Sciences
This paper discusses the effect of nonuniform varying communication delay on distributed consensus algorithms in discrete time. After introducing the delayed mathematical model, we first investigate the ergodicity of the delayed system using the properties of scrambling matrices. Subsequently, the effect of nonuniform varying delay on convergence is examined. It is shown theoretically that nonuniform delay is not detrimental to the convergence rate of the algorithm for directed acyclic graphs. The results are also illustrated with several numerical examples.
Load Management In A Distributed Multimedia Streaming Environment Using A Fault-Tolerant Hierarchical System,
2015
TÜBİTAK
Load Management In A Distributed Multimedia Streaming Environment Using A Fault-Tolerant Hierarchical System, Hadi̇ Işik Aybay, Mohammad Ahmed Shah
Turkish Journal of Electrical Engineering and Computer Sciences
In contrast to text-only forms of communications, multimedia uses a combination of audiovisual means alongside textual modes of communication. Streaming multimedia is such multimedia that is constantly delivered by a provider of the multimedia to a client. In streaming multimedia the streamed content is continually presented to and received by the end user. Distributed multimedia systems (DMSs) deliver multimedia content to end-users by means of distributed multimedia databases and distributed information servers. These DMSs are designed to deliver multimedia content over a network. A fault-tolerant redundant hierarchy (Red-HI)-based load management policy for a distributed multimedia streaming system is proposed in …
Rfid Card Security For Public Transportation Applications Based On A Novel Neural Network Analysis Of Cardholder Behavior Characteristics, Gürsel Düzenli̇
Turkish Journal of Electrical Engineering and Computer Sciences
This paper proposes a novel approach that applies neural network forecasting to security for closed-loop prepaid cards based on low-cost technologies such as RFID and 1-Wire. The security vulnerability of low-cost RFID closed-loop prepaid card systems originates mostly from the card itself. Criminal organizations counterfeit or clone card data. Although high-security prepaid cards exist, they are often too expensive for transport ticketing, and even their security is not guaranteed for a well-defined period of time. Therefore, data encryption systems are used widely against counterfeiting with success. However, it has not been possible to develop countermeasures with comparable success against cloning. …
A Model-Based Edge Estimation Method With Increased Edge Localization Accuracy For Medical Images,
2015
TÜBİTAK
A Model-Based Edge Estimation Method With Increased Edge Localization Accuracy For Medical Images, Mehmet Öztürk, Temel Kayikçioğlu
Turkish Journal of Electrical Engineering and Computer Sciences
This study proposes an improved method based on a nonlinear parametric model for intensity profile to increase the edge localization accuracy in medical images gathered from different imaging modalities. The edge model consists of three parameters associated with an edge point. It also takes into account local background intensity, noise, and blurring. The Marquardt-Levenberg algorithm is used to estimate the parameters because of its accuracy and good convergence rate. Performance of the proposed method is tested quantitatively by comparing the results with those of the well-known active contour method on synthetic vessel images. Qualitative comparisons on real MRI, coronary angiography, …
A Test And Simulation Device For Doppler-Based Fetal Heart Rate Monitoring,
2015
TÜBİTAK
A Test And Simulation Device For Doppler-Based Fetal Heart Rate Monitoring, Ahmet Mert, Mana Sezdi̇, Aydin Akan
Turkish Journal of Electrical Engineering and Computer Sciences
The Doppler effect is the preferred technique in fetal heart rate (FHR) monitoring devices. The main objective of the recent studies on the Doppler FHR has been to improve the accuracy. On the other hand, a reliable fetal heart simulator becomes essential for testing Doppler FHR monitoring devices. The motivation of this study is to design a reliable system that will be used to test Doppler FHR monitors. This device generates a similar Doppler frequency shift of fetal cardiac activity including the heart's wall and valve motions. The components of this system are basically a signal generator using a microcontroller …
Robust Speed Controller Design For Induction Motors Based On Ifoc And Kharitonov Theorem,
2015
TÜBİTAK
Robust Speed Controller Design For Induction Motors Based On Ifoc And Kharitonov Theorem, Bijan Moaveni, Mojtaba Khorshidi
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, robust PI controllers are designed to control the speed of induction motors based on a vector control strategy. The design methodology defines the robust stability and robust performance regions in the $k_{p}-k_{i}$ (PI controller coefficients) plane using the Kharitonov theorem. In the control system design procedure, a nonlinear induction motor is modeled as an uncertain linear model. The procedure of modeling the uncertainties is presented. The required scientific foundations for designing a robust PI controller are also introduced in the general case while the necessary equations are derived. In the final step, the design procedure for a …
New Metrics For Clustering Of Identical Products Over Imperfect Data,
2015
TÜBİTAK
New Metrics For Clustering Of Identical Products Over Imperfect Data, Zeki̇ Yetgi̇n, Furkan Gözükara
Turkish Journal of Electrical Engineering and Computer Sciences
This paper introduces the concept of product identity-clustering based on new similarity metrics and new performance metrics for web-crawled products. Product identity-clustering is defined here as the clustering of identical products, e.g., for price comparison purposes. Products blindly crawled over web sources, e.g., online marketplaces, have different description formats, where the features describing the same products differ in both number and representation formats. This problem causes imperfect feature vectors, where the vectors are considered to be not uniform in length and structure, with the features of various data types (numeric, categorical), and unknown vector structures. Furthermore, the product information usually …
Regulation Of Methane Gas Output From An Anaerobic Reactor System Using Moving Horizon $H_{\Infty }$ Control,
2015
TÜBİTAK
Regulation Of Methane Gas Output From An Anaerobic Reactor System Using Moving Horizon $H_{\Infty }$ Control, Fatma Yildiz Taşcikaraoğlu, Şeref Naci̇ Engi̇n
Turkish Journal of Electrical Engineering and Computer Sciences
In this study, the moving horizon $\mathcal{H}_{\infty }$\textbf{ }control used for tracking a desired methane gas output from an anaerobic wastewater treatment reactor is compared with classical $\mathcal{H}_{\infty }$ control and a proportional-integral-derivative controller. The nonlinear system is first linearized around the set of equilibrium and operating points selected, and then the linear matrix inequalities required to comply with the constraints and guarantee the stability are constructed. Finally, the experimental results are obtained by implementing the control method in a MATLAB environment. It is concluded that moving horizon $\mathcal{H}_{\infty }$ control yields satisfactory results.
3d Imaging For Ground-Penetrating Radars Via Dictionarydimension Reduction,
2015
TÜBİTAK
3d Imaging For Ground-Penetrating Radars Via Dictionarydimension Reduction, Muhammed Duman, Ali̇ Cafer Gürbüz
Turkish Journal of Electrical Engineering and Computer Sciences
Ground-penetrating radar (GPR) has been widely used in detecting or imaging subsurface targets. In many applications such as archaeology, utility imaging, or landmine detection, three-dimensional (3D) images of the subsurface region is required for better understanding of the sensed medium. However, a high-resolution 3D image requires wideband data collection both in spatial and time/frequency domains. Match filtering is the main tool for generating subsurface images. Applying match filtering with the data acquisition impulse response for each possible voxel in the 3D region with the collected data requires both a tremendous amount of computer memory and computational complexity. Hence, it is …
Detection Of Stator Winding Fault In Induction Motor Using Instantaneous Power Signature Analysis,
2015
TÜBİTAK
Detection Of Stator Winding Fault In Induction Motor Using Instantaneous Power Signature Analysis, Ahmet Küçüker, Mehmet Bayrak
Turkish Journal of Electrical Engineering and Computer Sciences
Stator interturn faults are one of the most common faults occurring in induction motors. Early detection of interturn short circuit is important to reduce repair costs. Axial leakage monitoring, zero-sequence components, negative sequence current, and motor current signature analysis have been used for fault detection in early states. In the paper, the instantaneous power signature analysis technique is used to detect these faults, and experimental results for healthy and faulty motors are shown and discussed.
A New Approach To The Development Of A Nonlinear Model For Micro-Pelton Turbines,
2015
TÜBİTAK
A New Approach To The Development Of A Nonlinear Model For Micro-Pelton Turbines, Mahmut Temel Özdemi̇r, Ahmet Orhan
Turkish Journal of Electrical Engineering and Computer Sciences
In this study, a new approach that is closer to the real turbine without abandoning the advantages of nonlinear modeling simplicity compromising the simplicity of the nonlinear model is proposed. The purpose of the study is to contribute to making theoretical studies of microhydroelectric power plants (MHPPs) more realistic. Studies on their control, especially frequency control, have increased with the expansion of grid-connected power plants. However, some problems have occurred when converting simulation studies of the frequency control to practical studies. The reasons for these problems are that the systems cannot be modeled completely. In this study, first, the nonlinear …
A Novel Asymmetrical Connection Balance Transformer For Traction Power Supply,
2015
TÜBİTAK
A Novel Asymmetrical Connection Balance Transformer For Traction Power Supply, Zhiwei Xu, Longfu Luo, Zhiwen Zhang, Yong Li
Turkish Journal of Electrical Engineering and Computer Sciences
Balance transformers can usually eliminate the zero sequence current and suppress the negative sequence current. This paper develops a novel approach for balance transformers, which is different from the traditional one with two-phase or three-phase symmetrical windings. First, the basic principle and the connected scheme of the transformer are clarified. Second, this paper derives the relationship between the primary and the second windings from a mathematical model for the new approach. Third, the balance condition (i.e. the neutral current in the primary side is zero) and the decoupling condition of the two-phase system are also obtained. Finally, the correctness and …
Optimal Backup Parent Pools For Resilient Multicast Trees On Peer-To-Peer Networks,
2015
TÜBİTAK
Optimal Backup Parent Pools For Resilient Multicast Trees On Peer-To-Peer Networks, Emrullah Turhan Tunali, Müge Sayit
Turkish Journal of Electrical Engineering and Computer Sciences
Due to churn as well as node and link failures in peer-to-peer (P2P) networks, providing resilient multicast is a challenging issue, particularly for overlay trees. In this work, we first study analytical properties of the backup parent pool that aims at improving the resilience of overlay multicast trees in P2P video streaming. We then present a novel greedy degree-constrained multicast tree construction algorithm that addresses the tradeoffs between maximizing resiliency, maximizing bandwidth utilization, and minimizing delay. The choice of essential design parameters is studied together with seamlessness of the streaming under a variety of fault scenarios. Simulation results indicate that …
Determination Of Electromagnetic Properties Of Steel For Prediction Of Stray Losses In Power Transformers,
2015
TÜBİTAK
Determination Of Electromagnetic Properties Of Steel For Prediction Of Stray Losses In Power Transformers, Leonardo Strac, Damir Zarko
Turkish Journal of Electrical Engineering and Computer Sciences
This paper introduces a method for determination of equivalent linear electromagnetic parameters (constant complex permeability and electrical conductivity) of nonlinear magnetic steel, which can be used in a time-harmonic finite-element simulation to yield the same losses in the volume of that material as the measured ones. The conductivity and the static hysteresis loop of the steel have been measured, from which complex permeability as a function of flux density has been extracted. The indirect measurement of losses in various samples of nonmagnetic and magnetic steel has been carried out using a physical model of a transformer core with a coil. …
