Elektrik-Elektronik Mühendisliği Bölümü / Department of Electrical and Electronics Engineering
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Browsing Elektrik-Elektronik Mühendisliği Bölümü / Department of Electrical and Electronics Engineering by Issue Date
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Publication Analysis of Single Flying Capacitor Converter by the State-Space Averaging Technique(IEEE, 1988) Bilgiç, Mehmet Oruç; Ehsani, M.; 1616The single flying capacitor converter (SFCC) is a two-quadrant power supply for energy storage and transfer system. It has applications in nuclear research and pulsed power systems in which superconductive coils are used in superconductive magnets. The authors derive analytical expressions for the time-averaged behavior of the SFCC by using the state-space averaging technique. Useful expressions are found for the average behavior of the SFCC. The results can be used in the design, control, and optimum operation of the system.Publication Analysis of inductor-converter bridge by means of state-space averaging technique (superconducting magnet energy storage)(1988) Bilgiç, Mehmet Oruç; Ehsani, M.; 1616The time-averaged behavior of an inductor-converter bridge (ICB) circuit has been analyzed using a state-space averaging technique. The application of the state-space averaging technique to the ICB circuit analysis is somewhat different from the well known DC-to-DC converter cases such as buck, boost, and flyback of Cuk converter analysis in that the first-order approximation of the state transition matrix will give trivial results. The results, which were previously obtained in infinite Fourier series form, are in closed form. A comparison is also made with the Fourier result. The ICB is a two-quadrant power supply for superconductive energy storage magnets. Closed-form expressions are found for the average current, voltage, and power behavior of the ICB. This application is somewhat different from the analysis of other DC choppers such as buck, boost, flyback, and Cuk converters in that the first-order terms are identically zero and the second-order terms have to be used.Publication Inverse Dual Converter (IDC) for High Power DC-DC Applications(IEEE, 1990) Ehsani, Mehrdad; Husain, Iqbal; Bilgiç, Mehmet Oruç; 1616The inverse dual converter (IDC), suitable for high-power DC-DC conversion applications, is presented. The IDC is a voltage source converter with an AC link and has been derived from an inductor converter bridge. This capacitor commutated converter is capable of continuous voltage step-up or step-down control over a wide range without the need of a transformer. In addition to high-frequency switching the converter is characterized by soft switching techniques, reducing constraints on the ratings of the switches. The average model developed with the help of gyrator theory provides sufficient information for control strategies and design considerations. The results of gyrator modeling and computer simulation are compared with experimental results obtained from a prototype IDC.Publication Topological Variations of the Inverse Dual Converter for High Power DC-DC Applications(IEEE, 1990-10-07) Ehsani, M.; Laskai, L.; Bilgiç, Mehmet Oruç; 1616DC to DC power converter topologies that are suitable for high-density, high-power supplies are presented. Topological variations on the basic inverse dual converter (IDC) circuit, such as the coupled transformer and the multiphase and multipulse derivation of the single-phase IDC, are analyzed, and simulation results are discussed. The topologies have most of the IDC features, such as buck-boost operation, bidirectional power processing, capacitive commutation for switches, and unlimited high-power capability. The multiphase, the coupled transformer, and the power distribution IDC topologies offer additional properties, such as significant power-density improvement isolation. AC tapping, and input-current reduction. A quantitative comparison between the single- and the multiphase IDC is presented.Publication Capacitively Coupled Converter (C3) for HighPower DC-DC Conversion(1991-07) Ehsani, Mehrdad; Bilgiç, Mehmet Oruç; Khan, S.; 1616The capacitive coupled converter for high-power voltage source DC-DC applications is described. Its steady-state and dynamic behavior are analyzed theoretically and by computer simulation. Factors affecting its operation and control are discussed and some design rules are presented. A proof-of-principle model of the capacitive coupled converter was constructed, and its waveforms were recordedPublication Inverse dual converter (IDC) for high power DC-DC applications(IEEE, 1993) Ehsani, M.; Husain, I.; Bilgiç, Mehmet Oruç; 1616A family of DC-DC converters suitable for high-power applications is introduced. The inverse dual converter (IDC) is capable of continuous voltage step-up or step-down control over a wide range of and without the need of a transformer. Experimental verification of the analysis is given for the simple single-phase IDC. Some of the more sophisticated members of the IDC family are described, and their characteristics and possible application, are mentioned.Publication Power converters as natural gyrators(IEEE, 1993-12) Ehsani, Mehrdad; Husain, Iqbal; Bilgiç, Mehmet Oruç; 1616The authors investigate the open-loop gyrator behavior of a class of DC-DC converters that are characterized by double bridges. If the switching frequency of the double bridge converter is high enough with respect to its natural frequencies, the converter can be viewed as a gyrator from its terminals. Unlike other gyrator modeling approaches for converters, the double bridge converters naturally behave as gyrators without any extra control circuits.Publication Capacitor coupled converter (C3) for high power DC conversion(IEEE, 1995) Ehsani, Morteza; Bilgiç, Mehmet Oruç; Khan, S.; Laskai, L.; Jeong, Seung-Gi; 1616The bang-bang controlled capacitor coupled converter (C3) is described in this paper. Due to the converter's inherent commutating property, the C3 can accommodate thyristors as well as high-power gate turn-off switches, due to zero-current switching transitions. The zero-current switching is achieved at no current stress increase, therefore, the topology is considered appropriate for high-power processing. DC and small signal AC models are derived for the bang-bang controlled C3, a design procedure is proposed, and simulation results are discussed. Finally, oscillograms from a proof of principle prototype circuit are presentedPublication Magnetically inflatable SPS with energy storage capability(IEEE, 1995) Ehsani, M.; Bilgiç, Mehmet Oruç; Patton, A. D.; Mitra, J.; 1616A new approach to superconductive magnetic energy storage (SMES) for solar power satellite (SPS) with inherent rigidity is introduced in this paper. The rigidity of this SMES originating from the electromagnetic forces within it, can eliminate the need for mechanical building blocks for support structure. This force can also be used for the deployment of the system in space. In addition, the storage capability of the system allows its use in low Earth orbit (LEO) which reduces the launching and transmission costs. The paper also discusses the basic design and the operation of the proposed SPS system.Publication Simulation of a C-Dump Switched Reluctance Motor Drive(1995) Özbulur, Veysel; Bilgiç, Mehmet Oruç; 202694; 1616Publication Torque Ripple Reduction of a Switched Reluctance Motor(1995) Özbulur, Veysel; Bilgiç, Mehmet Oruç; Sabanovic, A.; 202694; 1616Publication Torque Ripple Minimization of a Switched Reluctance Motor(1995) Bilgiç, Mehmet Oruç; Özbulur, Veysel; Sabanovic, A.; 1616; 202694This paper presents a simple technique to minimize torque ripple of a switched reluctance motor. The technique is based on the control of the sum of the square of the phase currents by using only two current sensors and analog multipliers. The simulation results and a proposed circuit are given. The advantages and its limitations of the proposed circuit are explained.Publication New architectures for space power systems(IEEE, 1995-08) Ehsani, M.; Bilgiç, Mehmet Oruç; Patton, Alton D.; Mitra, J.; 1616Electric power generation and conditioning have experienced revolutionary development over the past two decades. Furthermore, new materials such as high energy magnets and high temperature superconductors are either available or on the horizon. Our work is based on the premise that new technologies are an important driver of new power system concepts and architectures. This observation is borne out by the historical evolution of power systems both in terrestrial and aerospace applications. This paper introduces new approaches to designing space power systems by using several new technologies. Two new architectures are introduced: the current source current intensive system and the articulate system. Basic characteristics of these systems have been investigated. Some aspects of the articulate system architecture, as discussed in this paper can be implemented in the short term. Flexible AC transmission systems which are now undergoing rapid development and implementation, can be regarded as a subset of the family of control methodologies which constitute the realm of articulate systems.Publication Fuzzy logic based control of switched reluctance motor to reduce torque ripple(IEEE, 1997) Derdiyok, A.; İnanç, N.; Özbulur, Veysel; Pastacı, Halit; Bilgiç, Mehmet Oruç; 202694; 6012; 1616This paper presents torque ripple reduction of a switched reluctance motor (SRM) by using a fuzzy speed controller. For this purpose, current control is applied with a fuzzy speed controller. The fuzzy controller adjusts the value of reference current to keep speed constant. In this study, the nonlinear model of a SRM is used and the motor used in simulation is an 8/6 SRM with a C-Dump converter.Publication Improving performance of switched reluctance motor by fuzzy logic controller(1999-04) Derdiyok, A.; Inanc, N.; Özbulur, Veysel; Bilgiç, Mehmet Oruç; 202694; 1616This paper presents torque ripple minimization of a switched reluctance motor (SRM) by using a fuzzy controller, The nonlinear model of the SRM and the mathematical model of the converter circuit are driven. The motor used in both simulation and experiment is an 8/6 four phase SRM with a C-Dump converter. The applied fuzzy controller adjusts the value of the reference current to keep the speed of the motor constant. The results show that the fuzzy logic is effective in reducing the torque ripple of the motor, and compensating for the nonlinear torque characteristics. The experimental result is given for a current control algorithm, and it shows that the quite nonlinear model of the SRM is well defined.Publication 3-Phase Induction Motor Drive with PWM Modulator Using a 8-Bit Low Cost Micrcontroller(2004) Küçükgüzel, E.; Bilgiç, Mehmet Oruç; 1616This paper describes a study on a well studied subject, driving 3-phase induction motor. But the hardware used for the study is different than the conventional 16-bit microcontrollers or DSPs. The aim of the project is to lower the price of control hardware and achieve a satisfying performance with less expensive 8-bit microcontrollers.Publication Doku Analiz Yaklaşımına Dayanan Yeni Bir İris Tanıma Yöntemi(IEEE, 2005) Akan, Aydın; GÜRKAN, GÜRAY; 113297; 2918Bu çalışmada, iris yardımı ile kişi tanıma konusunda doku analizine dayalı yeni bir yöntem sunulmaktadır. İris görüntüleri bir ön işlemeden geçirildikten sonra doku analizine dayanan öznitelik vektörleri çıkarılmaktadır. Normalize edilen iris görüntüsü dikey logaritmik olarak örneklenir ve dairesel simetrik Gabor süzgeçlerinden geçirilir. Süzgeç çıkışları üzerinde kayan bir pencere altındaki piksellerin ortalama mutlak sapma değerleri öznitelik olarak elde edilir. Önerilen yöntem, iris ile kişi tanıma sisteminde aranan önemli niteliklerden ölçek ve dönüş ile değişmezlik özelliklerine sahiptir. Sistemin yazılım kısmı, Delphi derleyicisi ile Windows ortamında gerçeklenmiştir.Publication Texture Analysis Based Iris Recognition(2006-01) Akan, Aydın; GÜRKAN, GÜRAY; 113297; 2918In this paper, we present a new method for personal identification, based on iris patterns. The method composed of iris image acquisition, image preprocessing, feature extraction and finally decision stages. Normalized iris images are vertically log-sampled and filtered by circular symmetric Gabor filters. The output of filters are windowed and mean absolute deviation of pixels in the window are calculated as the feature vectors. The proposed method has the desired properties of an iris recognition system such as scale and rotation invariance. The system is realized in Windows platform using Delphi compiler.Publication An FPGA implementation of 2-D CNN Gabor-type filter(IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA, 2007) Saatçı, Ertuğrul; Cesur, Evren; Tavşanoğlu, Vedat; Kale, İzzet; TR10488; TR36339A field programmable gate array (FPGA) implementation of the Gabor-type filter is presented. The implementation uses the forward Euler approximation with optimal step size to solve the CNN cell-state equation. The FPGA is implemented on Xilinx Spartan XC3S400 device using 219 slices. An image of dimension 60 x 60 can be processed without using any external RAM only with the block RAM.Publication Lung Sound Noise Reduction Using Gabor Time-Frequency Masking(SPRINGER-VERLAG BERLIN, HEIDELBERGER PLATZ 3, D-14197 BERLIN, GERMANY, 2007) Akan, Aydın; SAATÇI, ESRA; TR112197; TR2918The Gabor expansion is a mathematical tool, which provides a joint time-frequency representation of a given signal by decomposing it into time-frequency elementary signals called Gabor atoms. It has been used in a variety of signal processing applications, including biomedical signal processing. In this paper we present a time-frequency masking technique based on Gabor expansion for both heart sound localization and reduction problem. Gabor coefficients of lung sound segments recorded from trachea are calculated and masked to remove the distinctive heart sound effects. Reconstruction of lung sound is achieved from modified Gabor coefficients without heart sound noise.