Mehmet Timur Aydemir

Kadir Has University | KHU · Department of Electrical and Electronics Engineering

High voltage high-frequency (HVHF) transformers have a crucial part in the realization of high voltage direct current (HVDC) isolated power supplies. Nevertheless, they are the bulkiest component in the system besides being one of the major contributors to the power losses. Special care is therefore required to design HVHF transformers. The main ob...

Nowadays, Wireless Power Transfer (WPT) technology is receiving more attention in the automotive sector, introducing a safe, flexible and promising alternative to the standard battery chargers. Considering these advantages, charging electric vehicle (EV) batteries using the WPT method can be an important alternative to plug-in charging systems. Thi...

Capacitive power transfer (CPT) technology is becoming increasingly popular in various application areas. Due to its limitations, such as low frequency, low coupling capacitance, and the high voltage stress on metal plates, the studies on high power CPT applications fell behind previously. Therefore, the wideband gap (WBG) semiconductor devices and...

In the past years, applications of Power Factor Correction (PFC) boost converter have increased significantly. One recent application field that requires an efficient PFC boost converter is the Wireless Power Transfer system (WPT). In this paper, the design of a single-phase PFC boost converter is presented. The proposed converter comprises three p...

Several methods have been proposed in the literature for the calculation of self and mutual inductance. These methods include the use of complex integral analysis, the necessity of having primary and secondary coils with the same dimensions and the limitations of the ratio of the coil dimension to the distance between the coils. To overcome these r...

This paper proposes a simple cascade PI controller for Buck converter to be used in impressed current cathodic protection (ICCP) systems which aim to operate in wide voltage and current ranges for any load condition. The Buck converter with cascade controller structure is a frequently used topology in ICCP systems to prevent buried steel pipelines...

Wireless power transfer (WPT) technology is getting more attention in these days as a clean, safe, and easy alternative to charging batteries in several power levels. Different coil types and system structures have been proposed in the literature. Hexagonal coils, which have a common usage for low power applications, have not been well studied for...

Thanks to the rapid advancement of power electronic components, High voltage dc (HVDC) power supplies are now being used in many different sectors including medical industries, military radar technology, telecommunications, and aerospace. However, the design of a high voltage dc power supply presents many challenges. Especially, selection of proper...

A wide variety of AC/DC power converter topologies have been developed in order to improve the system efficiency, input power factor and system redundancy for stationary battery energy storage systems. Due to the nature of high-power batteries, there is a big voltage difference between battery terminals from the end of discharge to the high charge...

DC-DC power conversion can take three main forms in the sense of level conversion: buck (step-down), boost (step-up) and buck-boost (step-up/down). DC-DC power conversion from lower voltage value to a higher voltage value is called step-up application. A step-up application can be done with and without isolation. Non-isolated and isolated step-up p...

In this paper, an analog circuit design for the precision reading circuit of the tactical grade accelerometer is presented. Quartz accelerometer is modeled mathematically by dividing its structure into subunits. This model has been transferred to MATLAB-SIMULINK environment to observe the effects of some parameter changes on the model. In the light...

This paper proposes the use of a control algorithm that can yield soft switching both at turn-on and turn-off of the inverter of series resonance converter (SRC) gas metal arc welding (GMAW) machines. The technique takes advantage of the band-pass filter characteristics of the SRC and controls the power by using switching frequencies that are subha...

This paper presents a simplified small-signal stability analysis method for low voltage (LV) inverter-based microgrids, in a generalized manner. The simplification is based on a simplified microgrid structure that relies on dominating inverter coupling impedances with respect to interconnecting line impedances of LV distribution networks. The analy...

Kısmi güç işleyen dönüştürücüler son dönemlerde batarya şarj devreleri, güneş enerjisi sistemleri ve uydu güç sistemleri için önerilmektedir. Bu devrelerin üstünlüğü, tam güç yerine kısmi güç kullanarak sistem verimini yükseltmek, daha küçük anma değerli yarıiletkenler kullanmak ve maliyeti düşürmektir. Literatürde bu amaçla önerilmiş çeşitli yapıl...

Elektrikli araçlara olan ilginin son yıllarda artması, elektrikli araçları daha pratik ve güvenilir şekilde kullanabilmek için yeni yöntem arayışlarını da beraberinde getirmiştir. Birçok uygulama alanında kullanımı gittikçe yaygınlaşan Kablosuz Güç Aktarım (KGA) Sistemleri, elektrikli araçların batarya dolum uygulamaları için yakın geleceğin seçene...

Phasor Measurement Units (PMU) are essential parts of smart grids. There are several algorithms to determine the placement of these units for optimal observability of the system. In this paper two different hybrid methods and Integer Linear Programming method have been used for the placement of PMUs in the power system of Afghanistan. One of the hy...

Electric vehicles are seen as a solution to depletion of energy and air pollution. As a result of this vision the idea of contactless battery charging has been widespread. Contactless energy transfer idea was first proposed by Nikola Tesla. The concept is based on the transfer of energy between two coils which are not on a common core through a ver...

On a power network, events are desired to be monitored to discover their reasons and to take preventive actions. Today, phase measurement units are used to obtain transient data of network, however these devices are expensive and it is not considered as a practical option to place one on each node of the network. Therefore, methods of estimating vo...

Flywheel energy storage systems have become an important research subject in recent years. They are also considered for space applications instead of hazardous and bulky electrochemical batteries. In this paper, a flywheel energy storage system has been designed for satellite attitude control systems. Power requirements of a small commercial satell...

In this paper, phase-shifted pulse width modulation full bridge topologies which are capable of switching at zero voltage are evaluated. Eight examples of these topologies have been studied in detail and compared in different aspects. After a detailed investigation, it has been decided to use zero voltage switching with current doubler and synchron...

Permanent magnet synchronous motors are preferred for high-performance applications because of their high power density and efficiency. Particularly, interior permanent magnet (IPM) synchronous motors are typically used in electric or hybrid vehicles due to their high efficiency and field weakening capability. One of the most important design consi...

Teknolojideki gelişmeler daha hassas cihazların üretimine olanak tanımıştır. Bu hassas cihazların zarar görmeden, verimli bir şekilde kullanılabilmesi için uygulanan gücün kalitesinin korunması gereklidir. Üretim santralleri ile iletim ve dağıtım hatlarındaki arızalar ve doğrusal olmayan yüklerin artması güç kalitesinde önemli bozulmalara sebep olm...

In this study, the hydrodynamic performance of a twin-blade hydrofoil has been numerically and experimentally investigated in three dimensions for tip speed ratios ranging between 1.5 and 5.5. The optimum geometric and flow parameters leading to the maximum value of the CL/CD ratio, which is the major design parameter of the wind and hydrokinetic t...

Standard airfoils historically used for wind and hydrokinetic turbines had maximum lift coefficients of around 1.3 at stall angles of attack, which is about 12°. At these conditions, the minimum flow velocities to generate electric power were about 7 m/s and 2 m/s for the wind turbine and the hydrokinetic turbine cases, respectively. In this study,...

Rocket Launcher Systems are mechanisms that carry rockets and orient them to targets. A Rocket Launcher System (RLS) has two degrees of freedom; it rotates about -z and -y axes to provide azimuth (yaw) and elevation (pitch) angles respectively. Azimuth and elevation axes are actuated by servo motors and a set of gears. The aim of the control for th...

Conventional three phase shunt reactive power compensation systems eliminate only the reactive power but do not contribute to the elimination of neutral current or voltage and current unbalance in three phase four wire systems. A hybrid wye and delta shunt compensation can be a solution for eliminating neutral current and unbalance besides compensa...

Fuel cell stacks and PV panels generate rather low DC voltages and these voltages need to be boosted before converted to AC voltage. Therefore high step-up ratio dc-dc converters are preferred in renewable energy systems. A new Z-source based topology that can boost the input voltage to desired levels with low duty ratios is proposed in this paper....

A synchronous buck DC–DC converter that can be used to produce hydrogen through electrolysis by using the energy generated from renewable energy sources has been designed and implemented. The reason for selecting this topology is that the voltage level at the output of renewable sources, such as solar cells and storage batteries, is about 12 V DC,...

Three phase pulse width modulated voltage source rectifiers are widely used in uninterruptible power supplyand motor drive applications due to their low input current THD, adjustable input power factor,and bi-directional power transfer characteristics.In this paper utilization of this type of rectifier at the front end unit of an industrial type un...

Three phase pulse width modulated voltage source rectifiers are widely used in uninterruptible power supplyand motor drive applications due to their low input current THD, adjustable input power factor,and bi-directional power transfer characteristics.In this paper utilization of this type of rectifier at the front end unit of an industrial type un...

A hybrid microgrid is proposed with the purpose of standardization having dedicated local controller algorithms for generalized indefinite instantaneous power Distributed Generators (DGs: Wind, PV) and definite instantaneous power DGs (sources that do not have intermittent characteristics). The first controller is based on DC link voltage control w...

Continuous input currents and high step-up ratios are desired from the dc-dc converters that work with renewable energy sources such as photovoltaic panels and fuel cells. Most dc-dc converters use transformers to have high step-up ratios. There is another type of converters that use coupled inductors, but they need to operate at high duty cycles t...

Flywheels have been under consideration to be used for energy storage purposes in space applications to replace electrochemical batteries. An electrical machine is used as a motor to store kinetic energy when the solar energy is available, and then the stored energy is converted back to electrical energy by running the machine as a generator when t...

A new dc-dc converter topology suitable for renewable energy sources such as photovoltaic panels or fuel cells is proposed in this paper. The converter which is a derived from Z-source converters uses coupled inductors to provide isolation and high conversion ratios. A big advantage of this converter is low switch voltage rating. A detailed analysi...

This paper is concerned with phase locked loop (PLL) structures for use in the control of line connected power electronic converters in three phase systems. Such converters have to operate under conditions in which the power system phase voltages are often unbalanced. The unbalanced and distorted line voltage vector as observed in the stationary re...

Control Moment Gyroscopes (CMG) and Reaction Wheels (RW) are systems used for satellite attitude control. These systems basically consist of an electric motor and a flywheel. Their control is very critical for the attitude control and health of satellite power system. Accuracy and control stability of the flywheel speed directly affect the stabilit...

Satellite attitude control systems have too many dynamic variables for all cases of operation. Therefore, their tests for all these conditions may not be possible or may require highly specialised test environments. As an alternative to these time consuming and expensive methods, real time digital simulation and hardware in the loop methods that ar...

Mechanical batteries have been drawing interest due to their longer life time and bigger depth-of-discharge ratings. Also, they do not have the adverse effects on the environment as the electro-chemical batteries. In mechanical batteries, an electric machinery is run in motor mode at a constant speed, storing kinetic energy in its inertia. When the...

This paper presents a new approach for the real-time digital simulation and hardware in the loop support for brushless dc motors. Sampling theory is used to model the interaction between the digital simulator infrastructure and the motor controller. A 6-step Voltage Source Inverter (VSI) is used as an illustrative example for the hardware in the lo...

Droop method is widely used to operate dc-dc converters in parallel. Although it is very simple and easy to use, poor regulation and uneven load sharing are the major limitations of the method. This paper presents a modified droop method to overcome these limitations. Proposed method is an adaptive technique that re-defines the droop coefficients a...

Parallel operation of several small rated converters may be preferred for various reasons instead of using a single, high power converter. Sharing of the load among the converters is a serious problem of parallel operation. There are basically two kinds of algorithms for sharing: systems using communication and systems using droop characteristics w...

Finite element analysis of an axial flux, permanent magnet, coreless stator, double rotor machine designed for a low power wind türbine application is presented. A real size model of the machine has been prepared by using Ansoft Maxwell, and electromagnetic analysis has been conducted. Induced stator voltages depending on the magnetic flux distribu...

Real time digital simulation and hardware in the loop testing have been finding widespread use in different applications. This paper presents a literature survey of the recent research done in the fýeld of real time digital simulation and hardware in the loop testing. Literature survey is supported by the experience gained during the application of...

A distributed power system consisting of two uninterrupted power supplies (UPS) is investigated in this paper. Parallel operation of the two sources increases the established power rating of the system. One of the sources can supply the system even when the other system is disconnected due to some faults, and this is an important feature. The contr...

This paper suggests the use of synchronous frame harmonic elimination technique in distributed power systems consisting of inverters with nonlinear loads. Inverters of the distributed system are controlled to share the active power. Power sharing is achieved without any communication between the units. To eliminate the harmonics caused by nonlinear...

An auxiliary circuit to accomplish soft switching in half-bridge converters is presented. The complete circuit is analysed, the design process, simulation and experimental results are given. Results show that the topology can be used even at high power levels. There is no control complexity involved. Efficiency is better than the classical topology...

A control method for parallel connected, hot- swappable boost converters suitable to use with fuel cells is described. Simulation results for the system are included. The simulation study has been carried out in MATLAB-SIMULINK. The dynamic model of the fuel cell is also included in the simulations. The control algorithm used in the design adjusts...

Active and reactive power sharing of parallel operating inverters has been investigated in this paper. The power sharing is achieved by adjusting the frequency and voltage amplitude of each unit. Each unit has its own controller and these controllers make sure that the total active and reactive power is shared by each unit in proportion with their...

High-temperature superconducting (HTS) material in bulk form is used to design a linear synchronous motor for an electromagnetic aircraft launch system. The motor is designed without an iron core. Stator coils are placed in the air while the permanent magnets used in conventional design of linear permanent magnet synchronous motors are replaced by...

Two basic linear motor designs suitable for an electromagnetic aircraft launch system (EMALS) have been presented in the paper. The motors have been designed with an emphasis on easy assembly and replacement even at the cost of slightly reduced performances. Both, linear permanent magnet synchronous motor (LPMSM) and linear induction motor (LIM) ar...

In this study, a 700 VA UPS has been designed and implemented. The system contains an input power stage, an internal battery charger, a driver unit, an inverter unit, an output power stage, a sampling unit, a control unit and 2×12 V dry cells. The input power stage provides ±15 V DC bias voltage to the battery charger. Battery charger continuously...

Realization of high power isolated DC-DC converters is largely dependent on managing converter parasitics and losses. In this paper, four different DC/DC converter topologies are compared in terms of their losses. The topologies include hard switched half bridge, switched snubber half bridge, zero voltage switching phase shifted full bridge and los...

This paper presents a new high frequency series resonant DC link topology derived by Y. Morai and T.A. Lipo (1988), wherein the resonant tank does not bring about peaky currents in any portion of the system. The characteristic overall-clamping mechanism permits lower-current-rating for the semiconductor devices, resonant capacitor and filter capaci...

Three phase simultaneous current pulse control for a high frequency series resonant DC link converter was achieved by utilizing a previously developed pulse trimming method and current peak limiting with a saturable core. Each resonant pulse is split to flow in three phases almost at the same time so that a very smooth sinusoidal output current wav...

A high-frequency series resonant DC link converter is utilized as a DC motor drive. This system generates a resonant current in a series link, and switching is done at zero current instants, reducing switching losses to a minimum value. A pulse density modulation (PDM) strategy, utilizing a current rectangular loop and an external motor speed feedb...

A pulse-width-modulated (PWM) extension of the series resonant converter is presented which reduces the dead time and improves the modulation strategy of this type of converter. With the addition of one thyristor and one diode to the 12 thyristors of a series resonant converter, pulses of link current of arbitrary width can be created. Simulations...

The use of a high-frequency series-resonant DC link power converter as a DC motor drive is described. This system generates a resonant current in a series link, and switching is performed at zero current instants, reducing switching losses to a minimum value. A pulse-density modulation (PDM) strategy, utilizing a current regulator loop and an exter...

zetçe Bu çalışmada uydulara yüksek hareket kabiliyeti kazandıran moment kontrol jiroskobu (MKJ) ve tepki tekeri/moment tekerinin (TT/MT) çalışma ilkeleri üzerinde durulmuştur. Dönen bir kütlenin aynı zamanda bir mekanik batarya olarak kullanılması fikrinden doğan volan sistemi kullanılarak doğru akım (DA) bara gerilim regülasyonunun yapılması kısac...

Magnetic permeability (µ) and resistivity (ρ) of the materials experience large variations during heating in induction steel heating furnaces (ISHF). Power unit operating at mid frequencies is expected to observe these variations and keep the output power constant and in the active region. It is not easy to obtain heat, pressure and position contro...

Induction heating is a widely preferred method for heating metals. However, its initial investment can be costly for simple processes. In this work, an affordable heating system has been developed for use in induction heating. Steel molds used in aluminum extrusion presses can be heated up to the extrusion temperatures by using this system.

ZET Bu çalışmada paralel bağlı buck türü dc/dc dönüştürücülerin çıkış akım ve gerilimlerindeki dalgalanmaların paralel bağlı dönüştürücü sayısına ve anahtarların doluluk oranına (duty cycle) bağlı olarak nasıl değiştiği incelenmiştir. Elde edilen sonuçlar sayısal benzetim ve deneysel çalışma sonuçlarıyla da karşılaştırılmıştır. 1. GİRİŞ Buck (düşür...