Yazar "Aksoy, Murat" seçeneğine göre listele

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    A Novel MPPT Method Based on Inflection Voltages
    (Elsevier Sci Ltd, 2020) Kesilmis, Zehan; Karabacak, Mustafa Alpaslan; Aksoy, Murat
    This study presents a novel maximum power point tracking method named inflection voltage method for photovoltaic systems. Inflection voltage method aims to find the global maximum power point using inflection voltages. It is known that multiple peaks occur in the power/voltage curves of photovoltaic arrays under partial shading conditions. Traditional methods such as perturb and observe and fractional open circuit voltage methods cannot perform MPPT with high performance in case of partial shading conditions. The inflection voltage method provides solutions to the problems of algorithms like fractional open circuit voltage and perturb and observe, such as failure to work under partial shading conditions and oscillation of output power. The success of inflection voltage method was tested first in the PSIM environment and then in the experimental setup developed. Computer simulations and experimental results showed that the proposed algorithm outperforms both fractional open circuit voltage, perturb and observe, particle swarm optimization under different partial shading conditions. (C) 2020 Elsevier Ltd. All rights reserved.
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    A novel two-stage MPPT method based on inflection voltages
    (Taylor & Francis Inc, 2022) Karabacak, Mustafa Alpaslan; Kesilmis, Zehan; Aksoy, Murat
    The electrical characteristic of a photovoltaic system is directly dependent on atmospheric conditions such as temperature, solar insolation, and even shading conditions. Hence, utilizing a maximum power point tracking hardware with a fast and accurate algorithm is crucial to obtaining the highest possible photovoltaic power. Several algorithms have been proposed in the literature to obtain maximum photovoltaic power, such as particle swarm optimization and perturb & observe variants. However, these algorithms provide less performance than optimal under partial shading. This study proposes a novel two-stage maximum power point tracking algorithm that equipped inflection voltages method and conventional perturb & observe algorithms. The proposed algorithm displays superior properties of both the inflection voltages method and the perturb & observe algorithms, such as predicting the location of maximum power points and high-speed climbing to these power points. A set of computer simulations are conducted in the PSIM environment to compare the performance of the proposed algorithm with particle swarm optimization, perturb & observe, and inflection voltages algorithms. Furthermore, a DC/DC converter-based experimental setup was produced and connected to a BK precision solar array simulator for experimental verification. The analysis results have shown that the proposed algorithm outperforms perturb & observe, inflection voltages, and particle swarm optimization methods in convergence speed and rate. Experimental and simulation results also show that the proposed algorithm successfully tracks the maximum peak in uniform and non-uniform irradiance conditions when others fail occasionally. On top of that, over 99% tracking efficiency is achieved, and the convergence time is also under 1 second.
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    Dönüm Gerilimleri Tabanlı Maksimum Güç Noktası Izleme Algoritmalarının Gelistirilmesi Ve Deneysel Dogrulaması
    (2022) Kesilmiş, Zehan; Aksoy, Murat
    Bilindigi üzere fotovoltaik (FV) sistemlerin elektriksel karakteristigi, sıcaklık, ısıma ve gölgelenme gibi atmosferik sartlara baglıdır. Bu nedenle FV sistemlerde hızlı ve basarılı maksimum güç noktası izleme (MGNI) algoritma ve donanımlarının kullanılması hem iktisadi hem de mühendislik bakıs açısından bir zorunluluktur. Literatürde, MGNI amacıyla parçacık sürü optimizasyonu (PSO) ve degistir ve gözle (P and O) varyantları gibi birçok algoritma önerilmistir. Ancak bu algoritmalar, göreceli olarak yüksek islem gücüne ihtiyaç duymanın yanında kısmi gölgeleme sartlarındaki basarıları da göreceli olarak düsüktür. 2020 tarihinde proje ekibi tarafından dönüm gerilimleri yöntemi (IVM) isimli bir MGNI yöntemi literatüre kazandırılmıstır. IVM global maksimum güç noktasının olustugu tepeyi tespit etmede basarı gösterse de yakınsana basarısı %95 civarında kalmaktadır. IVMnin izleme basarısı P ve O yöntemi yardımıyla iyilestirilebilir mi? arastırma sorusuna cevap bulmak için I2VM ismi verilen yeni ve özgün bir MGNI algoritması gelistirilmistir. Iki asamalı bir yöntem olan I2VMnin birinci asamasında IVMden ikinci asamada ise P ve O algoritmasından faydalanılmıstır. Bu sayede islem yükünü arttırmadan sade ve basarılı bir MGNI algoritması tasarlanmıstır. Proje kapsamında I2VMnin basarısı P ve O, PSO, ve IVM algoritmalarıyla karsılastırılmıstır. Karsılastırma sırasında PSIM benzetim yazılımı ve proje kapsamında temin edin BK precision SAS cihazı destekli deney düzeneginden faydalanılmıstır. PSIM benzetim ve deney sonuçları, önerilen algoritmanın MGNI basarısının P and O, PSO ve IVM yöntemlerinden daha iyi oldugunu göstermektedir. I2VM algoritması %99'un üzerinde izleme verimliligi ve 1 saniyenin altında yakınsama süresine sahiptir.
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    Fotovoltaik Paneller için Parametre Kestirim Sistemi
    (2020) Özcan, Kübra Akyol; Kesilmiş, Zehan; Aksoy, Murat; Karabacak, M. Alpaslan; Büyükgüzel, Bülent
    Fotovoltaik (FV) sistemlerin modellenmesinde panel parametrelerin doğruluğu büyük önem teşkiletmektedir. Bu çalışmada, FV panellerin parametrelerinin deneysel yolla belirlenmesini hedefleyen birsistem geliştirilmiştir. FV panellerin karakteristik eğrileri önerilen sistem ile örneklenmiş ve geliştirilenMATLAB yazılımına aktarılmıştır. MATLAB yazılımda, parametre tespiti için Newton Raphson, Secant,Bisection ve Regula Falsi yöntemleri uygulanmıştır. Kullanılan tüm kök bulma yöntemlerinin yüksekbaşarıyla parametre tespiti yapmasının yanında Secant yönteminin en hızlı yöntem olduğugözlemlenmiştir
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    Investigation of MPPT Algorithms under Partial Shading and Changing Atmospheric Conditions in PSIM Environment
    (Institute of Electrical and Electronics Engineers Inc., 2019) Kesilmis, Zehan; Karabacak, M. Alpaslan; Aksoy, Murat
    In this study, computer simulations were performed in PSIM environment in order to compare the success of Stochastic Beam Search, Perturb Observe, Fractional Open Circuit and Random Perturb Observe algorithms in partial shading and monitoring maximum power point under changing atmospheric conditions. The computer simulation model consists of 4 series connected solar panels, Buck type DC/ DC converter and C block which serves as micro controller. The simulation model provides a realistic and controlled environment for testing algorithms. The results of the study showed that the Stochastic Beam Search algorithm successfully performed the MPPT function under different shading conditions and changing atmospheric conditions. © 2019 IEEE.
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    Investigation of the Relationship between Vibration Signals Due to Oil Impurity and Cavitation Bubbles in Hydraulic Pumps
    (Mdpi, 2022) Yilmaz, Ozgur; Aksoy, Murat; Kesilmis, Zehan
    Although hydraulic pumps are frequently used in daily life, improper use due to oil analysis or oil contamination is ignored. There is no instantaneous inspection; instead, the oil is changed periodically at certain times, whether it is contaminated or not. Hydraulic systems operate based on Pascal's law, which states that the fluid will distribute the pressure equally to every point in a closed area. The fluid oil taken from an oil reservoir is moved into the pump by engine power. During this movement, as it passes through different pressure areas and different sections, undesirable events such as viscosity change and gas formation occur in the hydraulic oil. These formations collide with the outer walls and cause cavitation with respect to unwanted oil impurities. This cavitation causes unwanted vibration signals to occur in the normal working order of the system. As a result of cavitation, the particles that affect the lubricity and fluidity of the oil in the oil are mixed into the liquid and circulate freely. At the connection points, the blockage caused by the liquid in the pump cylinder block or the valve plate and the collisions of particles is effective. As a result, it creates vibrations of different frequencies. The frequency and amplitudes of these vibrations differ according to the degree of oil contamination. A method has been developed to find the degree of contamination of the oil circulating in the pump by looking at the amplitude and frequency of these vibrations measured from the motor body. There exist standards about the pollution of hydraulic fluid. With these standards, the maximum number of particles allowed for a given pollution level is defined. This topic is discussed in the conclusion to this study. This method has also been proven experimentally. Error and vibration analysis studies on pumps using a different approach are available in the literature. In these studies, pressure variation, total energy transmission, or artificial intelligence models were used to detect anomalies in the pump. In this study, the impurity rate of the oil was set at five different levels and the operating regime of the pump at each level was investigated experimentally. Rayleigh-Plesset and Zwart-Gerber-Belamri models, which are the most common cavitation models, were used to explain the bubble formation in the moving oil and the relationship of these bubbles with vibration. Frequency components were examined by the Discrete Fast Fourier Analysis method, where the operation of the pump was affected by the increase in oil impurity.
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    MEMS İvme Ölçerler için Analog Yapay Sinir Ağı Temelli Kontrolcü Tasarımı
    (2022) Kesilmiş, Zehan; Aksoy, Murat
    Bu çalışmada tek eksenli kapasitif MEMS ivme ölçer için yeni bir analog yapay sinir ağı temelli bir kontrolcü önerilmektedir. Bu kontrolcü giriş katmanında bir, gizli katmanda altı ve çıkış katmanında iki nöron olacak şekilde tasarlanmıştır. Bu kontrolcü, AMI C5N 0,6 ?m CMOS üretim teknolojisi kullanılarak Electric serim editörü ile tasarlanmıştır. Tasarlanan kontrolcünün başarısı çeşitli bilgisayar benzetimleriyle PID kontrolcüyle karşılaştırılmıştır. Benzetim sonuçları önerilen kontrolcünün tepki süresi, aşım ve ölçüm aralığı açısından PID kontrolcüden daha başarılı olduğunu göstermiştir.
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    Misalignment fault detection by wavelet analysis of vibration signals
    (2019) Yılmaz, Özgür; Aksoy, Murat; Kesilmiş, Zehan
    Asynchronous motors are frequently used in many industrial applications, especially pumps andfans. Placement, bearing and coupling faults are common faults in these types of engines.Misalignment error is a common type of error that is seen very often among these errors. This errormay cause efficiency decrease in a short run and vibration may cause short circuit and wear inmoving parts in the stator windings in a long run. Early diagnosis of such faults is important interms of machine health and productivity. In this study, loose connection and angular imbalanceof the asynchronous machine were investigated. In the experimental works, a 1 Phase 0.75 KWpower asynchronous motor, Y-0036-024A Electromagnetic Brake and SKF Microlog vibrationmeter were used during the measurements. The Frequency components of motor caused by thesettlement errors were investigated under the different loads. A loose assembly error and angularimbalance were investigated from the misalignment errors. The engine was run idle and withoutany positioning errors and measurements were taken from different points with the accelerometerand the frequency spectrum examined. Measurements are repeated when the misalignment errorsare occurred on purpose and the FFT frequency components were compared under the load of12.50Nm using magnetic brake. The results show that the FFT frequency components areexamined and the placement error can be determined with high success and accuracy. It has beenfound that harmonic components are formed in the frequency spectrum at 25Hz Coefficients. Afterthe settlement error is generated it is seen that, undesired frequency components that are unloadedare lowered under load when the frequency spectra is examined. In this study, theoretical andexperimental comparisons of settlement errors are made. Although many errors in this subject areexamined in the same publication in general, only the results of the settlement errors are examinedspecifically as a contribution to the literature. The results and graphs are presented comparativelyto the reader's knowledge.