Elektrik Elektronik Mühendisliği Bölümü Yayın Koleksiyonu

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

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Start date: 2020Publisher: search.filters.publisher.Ieee

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  • 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.
  • Conference Object
    Management of Open-Access Renewable Resources With Depensation Dynamics: Control Systems Perspective
    (Ieee, 2021) Cifdaloz, Oguzhan
    Renewable resources are being over exploited at an increasing rate. Institutions/governments are compelled to devise effective policies and strategies to sustainably manage renewable resources under social, ecological and environmental pressures that stem from increasing demand, model uncertainties, disturbances, and measurement errors. Open-access policies to harvest renewable resources are still widely used around the world. They are mildly regulated by implementing landing quotas, defining harvesting seasons, and/or constraining the technology used for harvesting. In many parts of the world, including the regions that are highly developed, open-access fisheries a refailing. In this paper, management of an open-access renewable resource (fishery) with depensation dynamics is formulated as a control systems problem and a strategy to sustainably manage the renewable resource is proposed. First, dynamics of an unregulated open-access fishery is described and its vulnerabilities are stated. Then, an easy-to-implement regulation strategy based on classical control systems ideas is proposed and its robustness characteristics are provided. The management policy (control law) is implemented via manipulating economic variables, i.e. by adjusting the (opportunity) cost of harvesting. An agent-based model is used to model the resource exploiters (i.e. fishermen). It is shown that a classical control law can be used to effectively manage an open access fishery subject to sampling effects.