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Öğe A Comprehensive Evaluation of Magnetic Coupler Configurations for Unmanned Aerial VehicleWireless Power Transfer Systems(Mdpi, 2026) Yilmaz, Mert; Cetkin, Erdal; Akca, HakanUnmanned aerial vehicles, which are widely used today, require human assistance to meet their energy needs. This dependency disrupts autonomous operation. At this point, wireless power transfer technology offers a promising solution for full autonomy. These vehicles can be easily charged by contactless power transfer between magnetic couplers in seemingly impossible locations. Coupler configurations are critical due to the size constraints of these vehicles. In current studies, analyses of transfer efficiency are conducted using one or two parameters. In this study, in addition to the coupler configuration, the effects of air gap, duty cycle, and magnetic core on efficiency were analyzed together. The performance of couplers with rectangular, circular, and double-D configurations was investigated through comprehensive simulations and experiments. The AC and DC efficiencies of the wireless power transfer system were analyzed by performing 46 experiments, while the operating frequency of the system was between 95 and 105 kHz, the input power was around 250 W. Simulations of the system and couplers were performed in MATLAB and Ansys. In the experiments, the highest AC efficiency was 98.9%, and the DC efficiency was 86.7%. The error margins in MATLAB and Ansys models are less than 1% and 4%, respectively.Öğe A Dynamic Energy Management Algorithm for Battery-Ultracapacitor-Based UPS Systems(Mdpi, 2025) Kircicek, Yagmur; Akca, HakanThis study presents a dynamic energy management algorithm (DEMA) designed for hybrid battery-ultracapacitor systems in uninterruptible power supply (UPS) applications. The proposed algorithm aims to enhance power reliability and extend battery life by dynamically coordinating energy flow between the battery and ultracapacitor under various operating modes. A single-phase UPS system was modeled and simulated in MATLAB/Simulink (Matlab R2025a version), and subsequently validated through experimental tests using an energy analyzer and an oscilloscope. The DEMA identifies and manages five operating modes, ensuring smooth transitions between grid-connected and backup states. During sudden load variations, particularly at a 1500 W step change, the ultracapacitor effectively supports the battery by supplying transient power, thereby reducing current stress and preventing deep discharge. Both simulation and experimental results confirm that the proposed algorithm maintains stable DC bus voltage, improves dynamic response, and achieves optimal energy utilization across all modes. The developed hybrid UPS control approach demonstrates high reliability and can be effectively implemented in critical load systems requiring uninterrupted power and enhanced battery longevity.Öğe A two-stage dc-dc converter with high voltage gain and reduced current ripple for efficient PV energy harvesting(Nature Portfolio, 2025) Akca, HakanPV systems require a dc-dc converter to operate at the maximum power point (MPP). However, switching based operation of these converters causes ripple current. This ripple current causes a voltage ripple due to the I-V characteristics of the PV panel. Both current and voltage ripple lead to power ripple and reduce the average energy extracted from the PV system. In this study, a two-stage boost converter (PTS-BC) topology is designed. The first stage, configured as an interleaved TP-BC fixed at \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$D=0.5$$\end{document}, drastically suppresses the input current ripple, while the second stage, operating as a conventional SP-BC, regulates the output voltage. The key novelty of this architecture stems from the use of dedicated stages for ripple cancellation and voltage regulation, thereby ensuring ripple-free PV input current across the entire duty range without requiring bulky input capacitors. The design has been validated through simulations and experimental studies performed on a 450 W PV prototype system. Within the examined operating range, duty cycle (D) changes from 10% to 80%, the PTS-BC provides a 12% and a 17% ripple reduction in input current ripple and power ripple, respectively, compared to conventional converters such as single phase boost converter (SP-BC), two phase boost converter (TP-BC), etc. In addition, PTS-BC requires significantly lower D than SP-BC and TP-BC for the same output voltage, thereby reducing conduction losses and voltage stress on switching devices in a two-stage configuration. The PTS-BC reaches a peak efficiency of approximately 98%, representing improvements of about 0.7% and 1.6% over the TP-BC and SP-BC, respectively. These results confirm that the proposed topology offers superior energy conversion performance and makes it a strong candidate for high-performance PV systems that require low input ripple and high efficiency.Öğe dc/dc Boost Converter Topologies and Experimental Comparison in Electric Vehicle to Grid Applications(Gazi Univ, 2024) Akca, Hakan; Aktas, AhmetIn applications that transfer energy from the electric vehicle (EV) to the grid, the direct current (dc)/dc boost converter circuits on the vehicle must be light, low volume, and high efficiency. To achieve this advantage, the inductor sizes used in non-isolated dc/dc converter circuits must be reduced. Synchronous and interleaved synchronous topology structures are used in dc/dc boost converter circuits. This study conducted experimental performance analyses of these two dc/dc boost circuits in a system with a battery group and a wireless EV charging structure. The study presents that in the interleaved synchronous dc/dc boost topology at the same power values, inductor currents and output voltage/current ripple decrease, and efficiency increases. The performance characteristics of the two circuit topologies under different operating conditions have been experimentally proven. It has been shown that using interleaved synchronous dc/dc boost converter topology is advantageous in EVs' high charge/discharge applications.Öğe Examination and experimental comparison of dc/dc buck converter topologies used in wireless electric vehicle charging applications(Ramazan Yaman, 2024) Akca, Hakan; Aktas, AhmetThe studies on Wireless Power Transfer (WPT) technology and peripherals in Electric Vehicle (EV) applications are intensifying. While the energy received from the WPT system is transferred to the EV battery, the direct current (dc)/dc converter circuits are used. The dc/dc buck converter topologies are one of them. The converter circuits must be highly efficient, lightweight, and compact to have a high range in EV vehicles. There are asynchronous buck, synchronous buck, and interleaved synchronous buck converter circuit topologies from the literature. In this study, the efficiency results of these circuit topologies were analyzed using MATLAB/Simulink and experimental studies. This study contributes to the literature by conducting circuit -level efficiency analysis and component -level power loss analysis. It has been observed that the interleaved synchronous buck converter circuit operates at 99% efficiency at 1066 W. In addition, it has been shared with the oscilloscope results that the current ripples of this circuit topology are lower than other circuit converters. Specifically, there has been a significant reduction of 56% in power losses, particularly in the interleaved synchronous buck converter (ISBC). This study analyzes the dynamic behavior of the dc/dc buck converter topologies, and results about their performance are given.Öğe FOTOVOLTAİK SİSTEM ENTEGRELİ ELEKTRİKLİ ARAÇ ŞARJ SİSTEMLERİNDE OPTİMUM KAPASİTENİN BELİRLENMESİ(2024) Akca, Hakan; Ayaz, RamazanBu çalışmada, fotovoltaik (FV) sistem entegreli ve şebekeye bağlı bir elektrikli araç şarj istasyonunda optimum FV kapasitesinin belirlenmesi için yeni bir yaklaşım ortaya konulmuştur. Gerçek ortamda FV panelin ürettiği güç değerleri, MATLAB FV modeli ve FV simülatör yardımıyla elde edilen sonuçlar ile karşılaştırılmıştır ve sonuçların birbiri ile uyumlu olduğu görülmüştür. Çalışmada 16,8 kWh kapasiteli bir elektrik araç bataryasının şarj edilmesi için gereken FV sistem kapasitesinin optimizasyonu amaçlanmıştır. Bunun için FV sistem optimum eğim ve azimut açıları belirlendikten sonra FV boyutlandırması yapılmıştır. Elektrikli araç bataryasının bir yıllık toplam enerjisinin FV sistemin bir yıllık toplam ürettiği enerji ile karşılanması amaç fonksiyonu olarak belirlenmiştir. Bu şartlar altında MATLAB modeli yardımıyla elde edilen sonuçlar 3,35 kWp’lik FV kapasitesinin bir aracın yıl boyunca ihtiyaç duyduğu enerjiyi karşılayabileceğini ortaya koymuştur. Bu çalışma, FV sistemlerin elektrikli araç şarj sistemleri için optimum kapasitenin belirlenmesinde etkili bir yöntem sunmaktadır.Öğe Investigation of the effects of various parameters on wireless power transfer efficiency(Elsevier Gmbh, 2025) Yilmaz, Mert; Cetkin, Erdal; Akca, HakanElectric vehicles have dominated the automotive market, especially in recent years. However, the charging problem that stresses drivers continues. Although conductive charging is an established technology, it still needs to meet user expectations fully. On the other hand, wireless charging technology attracts users' attention with dynamic charging features. Although this technology improves daily, efficiency is not at the desired level. In this study, a wireless power transfer system was designed for electric vehicles, and the factors affecting the charging efficiency were investigated. This system consists of an inverter, a compensation system, and a load. The efficiency of the system according to cable type, air gap, cooling, and pulse-width modulation parameters was observed through 40 experiments, each lasting 20 min. In addition to efficiency, the frequency behavior was also investigated. Experimental results were compared with models designed in MATLAB and ANSYS software. The average errors between the experimental and simulation results are 1.75, 2.03, 1.85, 1.58, and 2.00% for air gaps of 19-20, 55-56, 91-92, 127-128, and 145-146 mm, respectively. Power was transferred wirelessly with a minimum efficiency of 59.25% at a 145 mm air gap and a maximum efficiency of 85.74% at a 56 mm air gap in 300 W tests.Öğe Solar PV potential in Africa for three generational time-scales: present, near future and far future(Pergamon-Elsevier Science Ltd, 2024) Damo, U. M.; Ahmed, T.; Ozoegwu, C. G.; Sambo, As; Aktas, Ahmet; Akca, Hakan; Alam, MajbaulPower outage is a regular occurrence in most African cities due to increasing energy demand from population growth and commercial activities outstripping the grid capacity. This results in disruption to normal life putting stress on businesses and affecting development across the continent. This review paper investigates the potential of solar photovoltaic (PV) in African cities from three perspectives. Firstly, the potential of rooftop PV in the context of the political, economic, social, technical, legal and environmental aspects (PESTLE) is evaluated. Thereafter, sustainable waste management of solar PV panels is reviewed in anticipation for the upcoming wave of end-of life solar panels. Finally, the prospect of dual use building integrated photovoltaic (BIPV) as power generators and building components is investigated from case studies in Africa. Most studies highlight the strong potential of rooftop PV and BIPV due to the availability of high radiance in the continent. However, our review shows that affordability and lack of investment acts as a significant barrier to mass adoption of this technology which could be remedied by implementing appropriate energy policy and financing schemes. Alternative financing of PV products and service solutions such as leasing, pay monthly, pay-as-you-go, and subscriptions are emerging as popular options, and these approaches seem to act as drivers to market expansion. The review also emphasizes on the need for effective and sustainable waste management of solar PV products through implementing appropriately designed recycling schemes. This will need to be adopted now to ensure success and to prevent a waste management crisis in the future for the African continent.Öğe Synthesis, characterization, and investigation of photochemical and in vitro properties of novel Zn(II) phthalocyanine(Tubitak Scientific & Technological Research Council Turkey, 2024) Yildiz, Yasemin Baygu; Kabay, Nilgun; Yildiz, Burak; Omeroglu, Ipek; Durmus, Mahmut; Karagur, E. Riza; Akca, HakanA new nonperipheral zinc(II) phthalocyanine bearing octa carboxylic acid ethyl ester derivative substituted triazole attached propylmercaptothiobenzylmercapto derivative was synthesized via the tetramerization reaction of phthalonitrile. The photochemical in vitro photodynamic activity of zinc(II) phthalocyanine (ZnPc-I), such as human nonsmall cell lung carcinoma cell lines, was investigated in this study. The singlet oxygen generation property of novel zinc(II) phthalocyanine (ZnPc-I) was also examined due to the significantly high singlet oxygen quantum yield of ZnPc-I (FD = 0.66). The antiproliferative effects of ZnPc-I were also investigated on the A549 and H1299 cell lines, and the results demonstrated that ZnPc-I had a strong antiproliferative effect on both cell lines.Öğe YENİLENEBİLİR ENERJİ KAYNAKLARINA SAHİP EVSEL UYGULAMALAR İÇİN HİBRİT ANAHTARLI BİR DA/AA DÖNÜŞTÜRÜCÜNÜN FARKLI GÜÇ KOŞULLARI ALTINDAKİ PERFORMANS ANALİZİ(2025) Akca, Hakan; Selamogullari, Ugur S.Bu çalışmada, yenilenebilir enerji kaynaklarının konutlarda verimli kullanımı için hibrit anahtar yapısına sahip bir da/aa dönüştürücü ve kontrol yöntemi incelenmiştir. Konut uygulamalarında, elektrik güç talebinin büyük oranda 500 W ve altında kalması nedeniyle bu tip sistemlerde kullanılacak da/aa dönüştürücünün düşük güçlerde yüksek verimliliğe sahip olması kritik bir önem taşımaktadır. Da/aa devlerinde yaygın olarak kullanılan IGBT anahtarı yerine paralel IGBT-MOSFET kombinasyonu ile beraber yük akımı geri besleme yöntemi kullanılarak düşük güç seviyelerinde ve farklı güç faktörlerinde verimlilik artırılmıştır. Analizlerde maksimum güç talebinin yanı sıra günlük yük değişkenliği de dikkate alınmıştır. Örneğin, 100 W gibi düşük bir güç seviyesinde hibrit anahtar kullanımı, yalnızca IGBT kullanımına kıyasla güç faktörü 1,00 ve 0,85 için sırasıyla %6,3 ve %8,0 oranında verim artışı sağlamıştır. Bu durum, hibrit anahtar yapısının yalnızca yüksek değil, aynı zamanda düşük güç faktörü koşullarında da avantaj sağladığını ortaya koymaktadır.
