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    DA-DA Yükseltici Çeviricili Melez Birleştirilmiş Güç Kalitesi Düzenleyicisi Tasarımı ve Gerçekleştirilmesi
    (2016) Cuma, Mehmet Uğraş; Köroğlu, Tahsin; Demirdelen, Tuğçe; Tümay, Mehmet; Bayındır, Kamil Çağatay; İnci, Mustafa; Savrun, Murat Mustafa
    Dünyada ve ülkemizde, elektrik enerjisine olan talebin hızla artması ve gelişen teknoloji ile birlikte elektrik güç sistemlerine bağlı yük karakteristiklerindeki değişim elektrik güç kalitesi konusunun önem kazanmasına sebep olmaktadır. Elektrik güç sistemine bağlı ekipmanların ve son kullanıcı yüklerinin zarar görmesine veya yanlış çalışmasına sebep olan gerilimin veya akımın genliğindeki, frekansındaki ve dalga formundaki değişimler elektrik güç kalitesi problemleri olarak tanımlanmaktadır. Güç kalitesi problemlerinin kompanzasyonunda geleneksel kompanzasyon cihazlarının yetersiz kalması sonucunda ileri teknoloji güç elektroniği tabanlı kompanzasyon cihazlarının geliştirilmesine gereksinim duyulmuştur. Elektrik güç sistemlerinde karşılaşılan farklı güç kalitesi problemlerinin artmasıyla Dinamik Gerilim İyileştirici (DGİ)’nin ve paralel Aktif Güç Filtresi (AGF)’nin aynı DA bağına bağlanarak birleştirilmesiyle oluşturulan Birleşik Güç Kalitesi Düzenleyicisi (BGKD) geliştirilmiştir. BGKD; gerilim çukuru, gerilim tepesi, akım ve gerilim harmonikleri, akım ve gerilim dengesizlikleri, gerilim dalgalanması ve fliker gibi birçok güç kalitesi probleminin kompanzasyonunda ve reaktif güç kompanzasyonunda kullanılabilen gelişmiş bir sistemdir. Son yıllarda literatürde BGKD ile ilgili çalışmaların sayısı artmıştır ve çalışmalarda birçok farklı amaç için faklı BGKD topolojileri önerilmiştir. Bu topolojilerin içerisinde, DGİ’nin ve Paralel Melez Aktif Güç Filtresi (PMAGF)’nin aynı DA bağına bağlanarak birleştirilmesiyle oluşturulan Melez Birleşik Güç Kalitesi Düzenleyicisi (MBGKD)’nin, düşük maliyet ve etkin kompanzasyon özellikleri ile öne çıkması beklenmektedir. Bu projede, elektrik dağıtım sistemlerinde elektrik güç kalitesi problemlerine çözüm getirebilmek amacıyla yeni bir MBGKD topolojisi önerilmiştir. Önerilen MBGKD’ de DGİ’nin ve PMAGF’nin DA bağ bağlantısı çift yönlü izoleli DA-DA dönüştürücü ile gerçekleştirilmiştir. Önerilen MBGKD’ de, DGİ dengeli ve dengesiz gerilim çukuru ve gerilim tepesi kompanzasyonunu işlevlerini, PMAGF harmonik ve reaktif güç kompanzasyonu işlevlerini, çift yönlü izoleli DA-DA dönüştürücü ise gerilim çukuru/tepesi durumlarında çift yönlü güç transferini ve DGİ’nin DA bağ gerilimi sabit tutma işlevini gerçekleştirmektedir. Önerilen melez BGKD, sahip olduğu güç sistemi topolojisi ile literatürde ilk olmakla beraber bu topolojinin sağladığı yapısal ve işlevsel avantajlar ile literatürdeki BGKD topolojilerine göre birçok özgün yöne sahiptir
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    Design and Analysis of a High-Efficiency Resonant Converter for EV Battery Charger
    (2023) Erdoğan, Birand; Tan, Adnan; Savrun, Murat Mustafa; Cuma, Mehmet Uğraş; Tümay, Mehmet
    The interest in electric vehicle (EVs) components such as battery, battery chargers, and battery management systems is increasing in parallel with the spread of electric vehicles. One of the most critical of these components is battery chargers. Battery chargers are equipped with DC-DC converters with high efficiency, low cost, and wide output voltage range. In order to provide reliable operation of the battery charger, it is of great importance that the DC-DC converters are operated with a robust and stable controller as well as designed optimally. In this paper, a design method for a CLLC resonant converter-based bidirectional dc-dc converter (BiDC) is presented for a battery charger. The resonant converter, whose design details are presented, suggests a resonant system to be used in battery chargers with fewer components than the CLLLC converter, and similar voltage gain characteristics for bidirectional power flow operations compared to the LLC converter. The design procedure highlights performing the soft switching operation and determining the resonant tank parameters. In addition, the forward mode and reverse mode gain equations required for the system to operate in the desired output voltage range have been presented. The design procedures have been validated with a CLLC BiDC model with ratings of 1 kW, 400 V input / 300-450 V output in the PSIM environment. The performance results reveal that the zero voltage switching (ZVS) has been performed for primary-side MOSFETs under a wide load range.
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    Feeding Electricity Ring Grids with Minimum Interruption Using Fuzzy Logic Based Relay Coordination Scenarios Under Interruption Conditions
    (2020) Cuma, Mehmet Uğraş; Demiray, İrfan; Savrun, Murat Mustafa
    In order to secure continuous and high quality supply of electricity, it is essential to protect end users’devices and network equipments against malfunction from production to consumption. Therefore, theprotection of electrical equipment is essential and one of the devices performing the protection task iscalled the protection relay.Industrial plants and large consumers that possess a high variation in loads and variable generationresulting from the widespread implementation of distributed generation requires the adaptive operation ofrelays in protection systems to prevent undesired malfunctions.In this study, a novel fuzzy logic based adaptive relay coordination strategy with the advantages ofreduced computational load and fast computing for distribution networks is proposed. In order to evaluatethe performance of the developed relay coordination strategy, a real-world sample line for a ring-typedistribution network has been simulated in PSCAD/EMTDC environment. The performance of theproposed system is validated with simulation results for different case studies.
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    Performance Benchmarking of Active-Front-End Rectifier Topologies Used in High-Power, High-Voltage Onboard EV Chargers
    (2021) Cuma, Mehmet Uğraş; Savrun, Murat Mustafa
    High power onboard battery chargers employed in electric vehicles (EVs) and plug-in hybrid EVs\r(PHEVs) fed from three-phase mains typically consist of a two-stage structure as AC-DC and DC-DC\rstages. The AC-DC stage is also known as the active front end (AFE). While the AFE rectifies the mains\rvoltage, maintains the power factor, and provides a constant DC-link voltage to the DC-DC converter, the\rDC-DC converter stage regulates the charging current considering the charging algorithms in order to\rextend the battery service life. This study focuses on the selection of cost/performance effective AFE\rtopology that can be used in high power onboard chargers. Four different suitable AC-DC topologies are\rinvestigated: (i) 3-phase 2-level rectifier, (ii) 3-phase, 3-level neutral-point-clamped (NPC) rectifier, (iii)\r3-phase, 3-level T-type rectifier, and (iv) Vienna rectifier. In this study, the aforementioned AFE\rtopologies have been simulated on the PLECS/SpeedFit environment and compared in terms of\refficiency, losses, temperature, the number of switching elements, cost and cost/efficiency metrics. The\rperformance results of the aforementioned topologies have been evaluated under different operating\rfrequencies. The results reveal that the most suitable topology alternatives for the front-end AC-DC\rconverter are 3-phase 2-level PWM rectifier and Vienna rectifier. Although the 3-phase 2-level PWM\rrectifier is superior with its 12% cost advantage, fewer components, and ease of control advantages, it\rlags a little behind the Vienna rectifier in terms of total harmonic distortion.
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    Prediction of Ultimate Tensile Strength of Prestressed Concrete Strand Using Artificial Neural Network Model
    (2018) Cuma, Mehmet Uğraş; Özel, Hayrullah; Köroğlu, Tahsin
    The iron and steel industry is one of the essential sector for the industrial and economic development of a country. The most common problem in iron and steel industry is to determine the ultimate tensile strength of the product. The raw materials that are used in the Prestressed Concrete (PC) strand product are deformed under force and their shape and size are changed since the characteristics of them are not constant. To understand the material properties of the product such as the yield and the ultimate tensile strength, some mechanical tests are carried out. The product, the time and the labor loss occured in these mechanical tests reveal the need to develop a prediction method based on non-destructive measurement. In this study, the mechanical properties of PC strand product is predicted by using artificial neural networks (ANN). 'Feed-Forward Backpropagation (FFBP)' has been preferred since it is the most accurate network type for the current process. To determine the ultimate tensile strength, the data such as the load applied to the material (loadcell output), the DC voltage and the DC current of the induction furnace, the speed of the PC strand line, the temperature of the induction furnace, the temperature of the quench tank and the diamater of the PC strand product are collected from a real production line and are utilized as the input parameters of the ANN in the simulation environment. The study illustrates that the ANN model give a very good prediction of the ultimate tensile strength of PC strand.