Elektrik Elektronik Mühendisliği Bölümü Yayın Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/411

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Now showing 1 - 6 of 6
  • Article
    Design of a Novel Converter Between Li-Ion Battery and Supercapacitor To Feed Synthetic Aperture Radar Loads for Satellite Applications
    (int Journal Renewable Energy Research, 2020) Tulay, Gencer; İskender, İres; Iskender, Ires; Elektrik-Elektronik Mühendisliği
    For satellite applications the active duty life of a satellite depends mainly on the battery lifespan. The charging or discharging current has an important role in useful life of batteries. For this purpose, the converters used in power supplies including batteries should be accurately designed such that the large current of batteries can be prevented. The power converter proposed in this paper is used to transfer energy from battery to supercapacitor when SAR (Synthetic Aperture Radar) load is active. Accordingly, the lifespan of battery and hence the lifespan of satellite will be extended. Parallel to preventing the large discharging current of batteries the proposed converter has another important property such that it is able to vary the input voltage without having any stability problems. The operating performance of the converter that is composed of Weinberg and Buck converters is analyzed using PSpice software and the results of simulations are verified through experiments. The results show that how well the converter operates satisfying the conditions required for satellite applications.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 6
    Grid Connected Three-Phase Boost-Inverter for Solar Pv Systems
    (int Journal Renewable Energy Research, 2021) Demirkutlu, Eyyup; İskender, İres; Iskender, Ires; Elektrik-Elektronik Mühendisliği
    This paper presents a transformerless grid-connected three-phase boost-type inverter derived from the Swiss Rectifier (SR) and can be used in solar systems. The proposed boost-inverter retains the great advantages of the Swiss rectifier. Since the number of switches that are instantly switched with high frequency is only two, the switching losses are very low, therefore the proposed boost-inverter is very advantageous in terms of efficiency. Without having large transformer and electrolytic bus capacitors, the boost-inverter has an advantage in terms of size and weight. The switching states of the topology are given in detail. The operation principle of the boost-inverter is described with the help of equivalent circuits. A cascaded control method including current and voltage loops is designed. Simulation results are presented to validate the operation of the boost-inverter and show quality performance of the designed control approach.
  • Conference Object
    Citation - WoS: 6
    Citation - Scopus: 7
    Coreloss Estimation Via Long Short-Term Memory Model (Lstm) of Dry-Type Transformer Based on Fea
    (Ieee, 2021) Yildiz, Berat; Tamyurek, Bunyamin; Iskender, Ires; Kul, Seda
    Accurate estimation of losses is very important in transformer designs for energy systems. Therefore, in this study, a long short-term memory model (LSTM) was performed to predict the core loss of three-phase dry-type transformers based on Finite Element Analysis (FEA) analysis. Since, in ordinary multilayer networks, learning problems occur when the gradient value gets too small during backpropagation. LSTM, on the other hand, can store information better thanks to its extra layers that communicate. Thus, the learning process takes place more efficiently. The analysis and estimation processes were performed using a primary number of turns, excitation voltage, and three different cross-section area parameters. 486 data randomly selected from 506 data obtained by ANSYS/MAXWELL in the training of the LSTM model were used. The remaining 20 data were used in the testing process to measure system performance. The error obtained by the validation test is 0.15. It is very close to the simulated value, thus LSTM can be used as a reliable estimation method during the design stage.
  • Conference Object
    Citation - WoS: 1
    Citation - Scopus: 2
    Analysis of Lightning Impulse Effects on Three Winding Transformer Used in Solar System Based Ansys Maxwell
    (Ieee, 2022) Iskender, Ires; Yukselen, Emir
    Transformers are in more critical applications in the renewable energy world and having a transformer fail in such a cyclical power station can be disastrous. Over voltage or voltage strike is the most important phenomena for the transformers. Thus, the evaluating and estimating the effects and stresses of these sudden high voltages is important during the transformers life time operation and design stage. Accordingly in this paper the electromagnetic field analyses of the lightning impulse on Photovoltaic (PV) transformer are investigated using ANSYS Maxwell software. The 3D and 2D model simulation of the PV transformer is carried out to determine the electric field and voltage distribution on critical regions which can cause breakdown on insulation material and damage transformer windings and affects transformer working. Afterwards according to the simulation result, the subjected transformer was designed considering the relative critical regions and performs the full wave lightning impulse test in factory area to verify the dielectric strength of the transformer. This study provides better understanding of the lightning impulse voltage effects with localization of the critical regions on the PV transformer and helps to improve the withstand capability of the transformer against the lightning impulse voltages during the design and production stage.
  • Conference Object
    Citation - WoS: 3
    Citation - Scopus: 6
    A Novel Transformerless Single-Phase Three-Level Buck-Boost Inverter
    (Ieee, 2023) Demirkutlu, Eyyup; Iskender, Ires
    This paper proposes a novel transformerless, single-phase, three-level, buck-boost inverter. The proposed inverter can suppress the leakage current drawn from the input power source and provide a long-lasting solution for applications with a wide range and unregulated input voltage. Unlike similar topologies, in the proposed inverter there is no need to have a mid-point of DC sources or DC bus capacitors at the input side of the inverter. A single-phase, three-level, buck-boost inverter for realizing the power stage with 110-Vrms output AC voltage and a range of 100V-200V input DC voltage is investigated in this study. The proposed topology has been proven through theory, computer simulations, and experimental studies with SiC MOSFETs-based prototype of a 300-VA power supply. Theory, computer simulation, and experimental results are all correlated.
  • Book Part
    Citation - WoS: 10
    Citation - Scopus: 12
    Power Electronic Converters in Dc Microgrid
    (Springer international Publishing Ag, 2020) Genc, Naci; Iskender, Ires
    There are not many sustainable sources of energy other than renewable energy sources (RES), which are called solar, wind, water and various forms of biomass. Themost effectiveway to increase the use of renewable energy sources is to make use of renewable energy systems in villages, townships or small island-shaped districts where there are significant amounts of energy consumers. For this reason, the microgrid (MG) idea of small power system which is controllable, autonomous and balanced has been developed. Microgrids (MGs) playing a role of carrier for distributed generation resources (DGR), includes different distributed generation (DG) units, storage devices, energy converters, protection devices and load control devices. A MG generally includes renewable small power sources consisting of interconnected distributed energy sources with capacity of providing sufficient and sustained energy for a significant portion of the load. Different architecture types of MGs are presented in the literature. In recent years, the use of MGs being able to operate in two different modes depending on the island and grid-connected, has been expanded for DGR integration. Direct current (DC) microgrid has become an important subject of study in recent years as they have a more reliable and lower losses. A DC MG task distributes the DC power required by loads on a campus. Power generation in DC MG systems can be AC or DC; however, in most cases AC power supplies is converted to DC for distribution. The major advantage of DC microgridswhen compared toACsystems is its property of unidirectional power flow. This allows power control to be easily controlled by the power flow direction. In DC MG, the loads must be controllable to keep all loads at the DC range of the voltage in the default range and to regulate the voltage regulation. Besides voltage level and voltage regulation, the voltage ripple ratio should be kept as low as possible in DC microgrids. Therefore, power electronic converters are themost important part of the DC MG systems. There are although many studies published on MGs that control strategy and power electronic circuits make their important portions. It is obvious that the development of power electronic circuits and control methods has further enhanced the applicability of microgrids. In this study, the types, circuit structures and functions of power electronic converters used in DC microgrid are discussed. Power electronics converters used in DC MGs are grouped and evaluated according to their targets. These power electronic converters have been detailed in terms of AC-DC rectifiers, inverters (for AC loads) and DC-DC converter circuit types. The simulation results of some topologies have been evaluated.