Yazarlar
- Can, Erol(25)
- Uzun, Sinem(20)
- Yilmaz, Harun(18)
- Ting, Naim Suleyman(16)
- Kalkan, Orhan(15)
- Yesilbag, Yasar Ozkan(15)
- Sahin, Yakup(13)
- Yilmaz, Ilker(13)
- Cam, Omer(12)
- Celen, Ali(11)
- Ertugrul, Mehmet(11)
- Genç, Yasin(11)
- Huseyin, Ahmad(11)
- Salih, Ahmed Jalal Salih(10)
- Ganjehsarabi, Hadi(9)
- Tuzluca Yesilbag, Fatma Nur(8)
- Bakirci, Kadir(7)
- Ozgenel, Mehmet Cihat(6)
- Çırak, Çağrı(6)
- Acir, Adem(5)
- Acır, Adem(5)
- Amsil, Hamid(5)
- Astam, Aykut(5)
- Caglar, Bulent(5)
- Chakir, El Mahjoub(5)
- Demirci, Oğuz Kürşat(5)
- Kabach, Ouadie(5)
- Yesilbag, Fatma Nur Tuzluca(5)
- Akın, Fatih(4)
- Asgin, Mansur(4)
- Balli, Esra(4)
- Demir, Fatih(4)
- Demir, Zeynep(4)
- Dogan, Ahmet(4)
- Ekici, Selcuk(4)
- Karakoc, T. Hikmet(4)
- Katipoğlu, Okan Mert(4)
- Kilic, Bayram(4)
- Kılınç, Tuba(4)
- Manga, Müge(4)
Yayınlar
- ArticleYalnız künye2024DC–DC converter with multiple inputs and full isolated multi ports charging battery in photovoltaic energy systems
Can, Erol
The need for functional photovoltaic systems with multiple inputs used in energy storage devices is increasing day by day. In addition to having sufficient performance, these units are a good alternative to integrated converters with their low costs. In terms of these advantages, a multi-port DC–DC converter is recommended for solar energy systems in this study. In this multi-pot system, each port has a specific purpose. Two of them are renewable sources, one is the battery set and the other is the load port. Although this topology is developed for standalone systems, it can be easily adapted to other different applications. The system can provide energy from each input source independently or by combining them, and any renewable source can be charged to extend the life of the battery set, whether discharged or charged. While the system can provide energy in some periods of time without the need for input sources or by combining all elements in the system, a different renewable source can also be used to extend the life of the discharged or charged battery set. A few extra features make the system superior to other existing systems; First of all, the PV source and battery are directed to the same point. Sometimes, only the solar cell charges the battery, providing safe grounding for both, and secondly, the output is isolated from other connection points. These advantages are given by comparing them with existing systems. The advantage that is different from other topologies is that the proposed method can continue battery charging in 3 ways with the switches reserved for PVs. The first is discontinuous mode, the second is semi-continuous mode and the third is continuous mode. This mode of operation is preferred according to the amount of energy received from the sun. In this way, it offers a functional charging capability. After the proposed system design and numerical studies, it is also applied experimentally.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2024Thermal performance improvement of an air-cooled 18650 NMC battery module: A novel busbar design that acts as a turbulator
Kalkan, Orhan
Today, Lithium-ion batteries are preferred as popular energy storage tools in many fields such as electronic devices, especially electric vehicles. During the discharge of modules and packs formed by combining many battery cells, undesirable temperature increases are experienced due to excessive heat generation. Thus, thermal management of the battery packs is crucial. In this work, thermal and hydraulic performance analysis of the two air-cooled 18650 NMC battery modules, one with a novel designed twisted busbar and the other with a conventional busbar, are performed numerically. Temperature and pressure drop predictions are achieved at different values of air inlet velocity, discharge rate, depth of discharge, and twist diameter of busbar using CFD method. Besides, the Multi-Scale Multi-Domain battery model is validated experimentally. According to the numerical results, the novel designed twisted busbar provides 1.84 %, 2.93 %, and 3.81 % reduction in maximum battery module temperature for 5 m/s air inlet velocity under discharge rates of 2C, 3C and 4C, respectively. The average battery module temperature drops by 6.6 °C thanks to the use of a twisted busbar. Using a twisted busbar results in a maximum pressure drop increase of 119 Pa compared to the conventional busbar. As the twist diameter of the busbar increases, the battery temperature decreases significantly, and the pressure drop increases, especially at high air velocity conditions. In addition, when the twist diameter increases from 5 mm to 15 mm, the weight/volume ratio increases by approximately 0.9 %.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2024H2S gas sensing behavior of 2-D V2O5 nanowire network structure
Yıldırım, M. Ali; Tuna Yıldırım, Sümeyra; Karademir, Mert; Çağırtekin, Ali Orkun; Ateş, Aytunç; Acar, Selim
In this study, a nanowire network-based V2O5 nanostructure, designed as the active surface in H2S gas sensors, was produced using an environmentally friendly method known as hydrothermal synthesis. The morphological, structural, and electrical properties of the produced nanostructure were characterized using various measurement techniques. XRD, SEM, and EDX analyses confirmed that the nanostructure was in a pure monoclinic phase, had a two-dimensional (2-D) nanowire network morphology, and was deposited stoichiometrically. From UV–Vis analysis, the energy band gap value of the nanostructure was calculated to be 2.65 eV. In gas sensing measurements conducted between 27 °C and 102 °C, the optimal operating temperature of the fabricated sensor was determined to be 42 °C. At this temperature, which is close to room temperature, the sensor exhibited a high sensitivity of 21.16 % for 50 ppm H2S gas, along with good selectivity, stable repeatability, and baseline stability. Moreover, for 2 ppm H2S gas, the response and recovery times were 39 s and 58 s, respectively. A comprehensive electrical analysis of the sensor was carried out through impedance spectroscopy measurements over a wide temperature range. Our findings indicate that the 2-D V2O5 nanowire network structure (NNS) results in several notable effects, including low operating temperature, high selectivity, and stability for H2S gas, demonstrating considerable potential for industrial applications.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024Immersion cooling of a cylindrical battery module: An optimum configuration using CFD, NSGA-II and desirability function approach
Kalkan, Orhan
Immersion cooling offers promising advantages for cylindrical battery modules, particularly in applications where compact design, efficient thermal management, and enhanced safety are critical factors. In this study, the geometric, thermal, and dynamic parameters of an immersion-cooled battery module with 14 NCM cylindrical cells are analyzed using CFD methods. The developed battery model is experimentally validated, establishing the constraints through numerical analysis of the impact of design parameters on response values. The design parameters are optimized using a multi-objective optimization technique. The study models the battery module with mineral oil cooling and examines the impact of each parameter on variables such as maximum battery module temperature (Tmax), pressure drop (ΔP), maximum temperature variance (ΔTmax), and battery module mass index (Im). A Design of Experiment set, created with Central Composite Design (CCD), is solved using CFD methods, and quadratic correlation equations are derived using backward regression. The regression models for Tmax, ΔTmax, ΔP, and Im show high accuracy with R2 values close to 1.0. Optimization is performed using the entropy weight-based composite desirability function approach, yielding optimum values for cell center spacing (t), coolant mass flow rate (ṁc), and coolant inlet temperature (Ti) at 20.606 mm, 1.5 kg/s, and 23 °C, respectively. The optimized design sets are validated through CFD analysis, showing a maximum deviation of 4.27 %. Reducing t boosts thermal performance but lowers hydraulic performance, while the reverse occurs for ṁc. As Ti decreases, effective cooling improves, but temperature uniformity suffers.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024Analysis of hybrid AC/DC transmission system: A Turkey case study
Karaca, Eda; Nuroğlu, Fatih Mehmet
The need to transmit energy in the most effective way arises in parallel with the demand for energy in developing countries. As the amount of transmitted power increases, transmission lines can become overloaded, causing a blackout. This study aims to increase the transmission capacity without experiencing right-of-way problems by converting Turkey's existing high voltage AC systems to hybrid AC/DC systems. With such a design, it is aimed at providing more efficient and continuous transmission by using the high-voltage DC system's low-loss feature at long distances. Using the 400 kV double circuit line structure, the existing electricity transmission system is modelled using real data in the DigSILENT PowerFactory. The electromagnetic fields that will occur due to the use of AC and DC circuits on the same tower in such a transformation situation are analysed with FEMM 4.2, based on the finite element method. The compliance of the electromagnetic fields that will occur with the use of hybrid 400 kV AC and 500 kV DC was determined in the study. In addition, according to the simulation results, it is predicted that in the case of hybrid AC/DC transmission, the current transmission capacity would increase and the losses would decrease.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024Exploring thermal flow dynamics in pressurized water reactors using hybrid graphene nanoplatelet coolants
Uzun, Sinem; Genç, Yasin; Acır, Adem
This study investigates the impact of hybrid nanoparticles on the temperature of nuclear reactor coolant, with a focus on graphene nanoplatelet (GNP)-based hybrid nanoparticles. Sixteen different hybrid nanofluids were analyzed, and their performance was compared with a standard water-based coolant. The criticality values were obtained through MCNP modeling, revealing that higher nanoparticle ratios led to increased criticality, with the highest value of 1.3239 observed in GNP-Fe3O4 + Al2O3 nanofluids (0.05 wt%) and the lowest value of 1.2935 in GNP–Fe3O4 + SiO2 nanofluids (0.001 wt%). Temperature variations showed that increasing nanoparticle concentrations resulted in slightly higher temperatures, with a maximum of 611.97 K for 0.05 vol.% GNP nanoparticles. Additionally, the departure from nucleate boiling ratio values were consistently above the safety threshold of 2.08, with the lowest value of 3.657 for GNP–Fe3O4 + SiO2 nanofluids (0.05 vol.%). These findings suggest that hybrid nanofluids, particularly those with higher nanoparticle ratios, can enhance the thermal performance and safety margins of nuclear reactor coolants, offering a promising avenue for future research and application.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2024Optimizing neural network models for predicting nuclear reactor channel temperature: A study on hyperparameter tuning and performance analysis
Uzun, Sinem; Yildiz, Eyyüp; Arslantaş, Hatice
This study emphasizes how important accurate prediction of channel temperatures in nuclear reactors is for safety and operational efficiency. While traditional methods require long and complex processes such as kernel modeling and mathematical simulations, artificial neural networks (ANN) provide more efficient predictions by accelerating this process. The superior ability of ANNs to process large data sets is intended to demonstrate that this study will provide a valuable alternative compared to conventional methods and increase the accuracy of reactor temperature predictions. In this study, the training performances of Artificial Neural Network (ANN) developed to determine the nuclear reactor channel temperature with different hyperparameter combinations were analysed. It was conducted several experimental studies to assess the influence of hyperparameters on our model for nuclear reactor parameter data prediction. The training and validation results indicates that learning rate, hidden layer sizes and number have critical effects for the more precisive prediction. It was observed that models with a learning rate of 0.05 and 0.5 achieved successful learning with less fluctuation in training and validation errors. When looking at hidden layer sizes, networks with 32 and 64 neurons performed better than networks with 16 neurons. For the test phase our model can successfully predict data with slight error margin. As a result, we demonstrated that neural networks are a powerful tool in nuclear reactor channel temperature prediction through our proposed model.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2023A novel capacitor-voltage reduced bidirectional PWM DC-DC buck-boost converter for renewable energy battery charge system
Sahin, Yakup; Ting, Naim Suleyman; Yesilyurt, Huseyin
A novel capacitor-voltage reduced bidirectional (CVRB) PWM DC-DC buck-boost converter is presented in this study. Compared to the conventional bidirectional buck-boost converter, the proposed converter has a lower voltage rating filter capacitor. Accordingly, the given converter has a lower cost and higher power density than the conventional buck-boost converter. Additionally, the proposed converter is more efficient due to the direct power transfer feature. Besides, the semiconductor switches have no extra voltage/current stress. The theoretical analysis of the converter is made, and its mathematical analysis is presented. The novel converter is experimentally operated in both the buck and boost modes. The experimental waveforms are shown for both operations. The proposed converter is operated in 100 W output power and 20 kHz switching frequency conditions. The efficiency of the proposed converter is 95.6% for the boost mode operation and 95.1% for the buck mode operation at the nominal output power.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2023Performance and entropy production analysis of angle blade turbulators used to increase heat transfer
Firat, Ilker; Karagoz, Sendogan; Yildirim, Orhan; Yilmaz, Mehmet
In this study, the effects on thermal performance and entropy production of new type turbulators with different blade angles and numbers, which are placed in a circular shaped pipe and manufactured in a 3D printer, were investigated experimentally. According to the experiments performed in the Reynolds number (Re) range of 7007–13,982, the Nusselt numbers of the 60°, 70° and 80° fin angle turbulators are, respectively, compared to the supported plain pipe; increased by 82.09%, 98% and 105.83%. Due to the increase in the blade angle, the maximum thermal performance was obtained as 1.542 for the 80° blade angle turbulator for Re = 12,538. The thermal performance factors of the 80° and 70° blade angle turbulators were found to be 1.048 and 1.039 times higher than the 60° blade angle turbulators, respectively. It was determined that the thermal improvement factor of the 80° blade angle turbulator is 1.008 times higher than the 70° blade angle turbulator. In terms of the second law, the maximum entropy production increase of the finned turbulators compared to the supported plain pipe was 153.96% at Re = 8387, in 3 turbulators with 80° fin angles. It has been determined that 1 turbulator model with 60° blade angles is more advantageous compared to the turbulators with 70° and 80° blade angles, since it produces the lowest entropy. In addition, it has been concluded that the most suitable turbulator model in terms of thermal performance is 3 turbulators with 80° blade angles. Graphic abstract: [Figure not available: see fulltext.]
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2023Towards A Political Economy of Renewable Energy: Does Democracy and Globalization Matter for Central and Eastern European Countries (CEECs); [W kierunku ekonomii politycznej energii odnawialnej: czy demokracja i globalizacja mają znaczenie dla krajów Europy Środkowej i Wschodniej (CEEC)]
Cengiz, Orhan; Manga, Müge
Renewable energy policy is one of the remarkable parts of the sustainable development path. However, the polit-ical-economic dimension of renewable energy policies is not so much widely discussed. Besides, democracy and globalization are essential factors affecting renewable energy. Hence, this paper examines the relationship between renewable energy consumption, democracy, and globalization in the Central and Eastern European Countries (CEECs) during the period 1995-2021. Economic growth and CO2 emissions are used as control variables in the model. The study employs the panel vector autoregressive (PVAR) estimation technique to quantify the relation-ship between renewable energy consumption, democracy, and globalization by including economic growth and CO2 emissions. The findings from the PVAR analysis suggest that participatory democracy and globalization pos-itively affect renewable energy consumption, while liberal democracy, economic growth, and CO2 emissions have a negative impact on it. Furthermore, the PVAR Granger causality test outcomes indicate an interactive causal relationship between variables.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2023NUMERICAL INVESTIGATION OF A SERPENTINE-TUBE COLD PLATE COOLED LITHIUM-ION BATTERY UNDER WIDE PARAMETRIC CONDITIONS
Kalkan, Orhan; Celen, Ali; Bakirci, Kadir
This paper examines the thermal management of a commercial 20 A h lithium ferro phosphate battery with the cold plates containing the serpentine tube structure, which is frequently preferred in heat exchanger applications. A numerical analysis is performed to explore the battery surface temperature distribution under varying operating conditions. In the study, an experimentally verified electrochemical thermal compound model was created and temperature distributions at the end of discharge at 1C, 3C, and 5C rates are obtained. The effects of different inlet temperatures (15°C, 25°C, and 35°C) and volumetric flow rates (0.1 L/min, 0.6 L/min, and 1.1 L/min) of the coolant on the two vital parameters of battery thermal management –- maximum battery temperature and maximum battery temperature difference –- are investigated for each discharge rate. As a key finding in this study, there is an acceleration of temperature variation from the middle part of the battery with the minimum temperature to the terminals with the maximum temperature, at the end of the discharge, in the use of a serpentine cold plate. Under the conditions where the coolant flow rate is maximum and the inlet temperature is minimum, the highest maximum temperature difference is 14.4°C, while the lowest maximum temperature difference is 10.8°C under the conditions where the coolant flow rate is minimum and the inlet temperature is maximum. Besides, the correlation equations in which the adjusted R2 values for maximum battery temperature difference and maximum battery temperature are 98.0% and 99.6%, respectively, are developed.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2023Colorless distributed combustion characteristics of hydrogen/air mixtures in a micro combustor
Yilmaz, Harun; Karyeyen, Serhat; Tepe, Ahmet Ümit; Brüggemann, Dieter
Colorless distributed combustion technique enables less pollutants emissions for a fuel/oxidizer mixture to be combusted. In this study, colorless distributed combustion characteristics (CDC) of hydrogen/air mixtures were numerically investigated in a micro combustor to overcome the difficulties associated with micro combustion and to obtain a more uniform temperature profile on the outer wall. To that end, hydrogen/air combustion was simulated by using ANSYS/Fluent CFD code at a constant equivalence ratio (1.0) and thermal input (100 W) and different mixture inlet temperatures of 300 K, 600 K and 1000 K to seek colorless distributed combustion. CDC conditions were tried to be achieved by decreasing the oxygen concentration from 21 % to 9 % at an interval of 3 %. In conclusion, colorless distributed combustion conditions could be achieved at different O2 concentrations, irrespective of the mixture inlet temperature. At 300 and 600 K, such conditions did not make any positive contribution to the power output of the micro combustor. Nevertheless, at 1000 K and 9 % O2 concentration, all combustion and emission performance metrics were improved in a manner that could increase the power output of the micro power generator.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2023Effects of hydrogen addition on combustion and flame propagation characteristics of laser ignited methane/air mixtures
Yilmaz, Harun; Schröder, Lukas; Hillenbrand, Thomas; Brüggemann, Dieter
In this study, effects of hydrogen addition on combustion and flame propagation characteristics of methane/air mixtures were investigated in a constant volume combustion chamber. Tested gas mixtures are 100% CH4, 05% H2 – 95% CH4, 10% H2 – 90% CH4 and 15% H2 – 85% CH4, and such mixtures were ignited using a passively Q-switched Nd:YAG laser ignitor which has a pulse energy of 12.3 mJ, pulse duration of 2.4 ns and wave length of 1064 nm. A Schlieren setup coupled with a high-speed camera enabled evaluating flame propagation behavior, while pressure curve analysis provided necessary data for characterization of combustion properties. Additionally, lean flammability limits of gas mixtures were also determined at the test conditions. The unique properties of hydrogen (such as low density, high reactivity, high diffusivity etc) widened lean flammability limit. Rate of pressure rise and measured pressure values increased with hydrogen addition, regardless of the air-fuel equivalence ratio (λ). Lastly, hydrogen addition uniformly affected flame propagation characteristics and flame luminosity. Combustion process became more stable with hydrogen addition.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2023Experimental Investigation on Single-Phase Immersion Cooling of a Lithium-Ion Pouch-Type Battery under Various Operating Conditions
Celen, Ali
The selection of a battery thermal management technique is important to overcoming safety and performance problems by maintaining the temperature of batteries within a desired range. In this study, a LiFePO4 (LFP) pouch-type battery having a capacity of 20 Ah was experimentally cooled with both air and liquid (immersion cooling) techniques. Distilled water was selected as the immersion fluid in the experiments, and the impact of discharge rate (1–4C), immersion ratio (50–100%), and coolant fluid inlet temperature (15–25 °C) on the battery temperature were investigated during the discharge period. The experiments revealed that maximum temperatures were reached at approximately 45 °C and 33 °C for air and distilled water cooling techniques, respectively, at the discharge rate of 4C. The average and maximum battery surface temperatures can be reduced by 28% and 25%, respectively, with the implementation of the liquid immersion technique at the discharge rate of 4C compared to the air technique. Moreover, the experiments demonstrated that the maximum temperature difference could be lowered to 4 °C by means of 100% liquid immersion cooling at the highest discharge rate, where they are approximately 11 °C and 12 °C for air and 50% for immersion cooling, respectively. In addition, it was observed that the coolant fluid inlet temperature has a significant impact on battery temperature for %100 liquid immersion.
RDL Kalıcı Kaydıİncele - Conference ObjectYalnız künye2023Nonlinear Convergence Factor Based Grey Wolf Optimization Algorithm and Load Frequency Control
Hocaoglu, Gokce Sena; Cavli, Nazlican; Kilic, Elcin; Danayiyen, Yahya
In this paper, various type of nonlinear convergence factors based Grey Wolf optimization (GWO) is proposed to optimally compute the Proportional-Integral-Derivative (PID) controller gains to control the grid frequency in a single area power system. The PID gains in the controlled system are optimally determined by using GWO algorithm, considering the cost function, integral of time-weighted absolute error (ITAE). The efficiency of the designed control system is verified under constant and variable loads, and the comparative results are given for controlled and uncontrolled cases. Moreover, the GWO algorithm is investigated by using linear and nonlinear convergence coefficients comparatively. The model of the control system is constructed using MATLAB, and the results indicate that the transient and steady state responses are superior to those of the linear coefficients when the nonlinear convergence coefficients are applied in GWO.
RDL Kalıcı Kaydıİncele - Conference ObjectYalnız künye2023Design of an Optimal PI Controller for Time-Delayed Two-Area LFC-VID System
Hasen, Suud Ademnur; Aydin, Omer; Ayasun, Saffet
Growing deployment of renewable energy sources (RES) may lead to oscillations in the system frequency caused by reduced inertia, while communication networks generate time delays that might jeopardize system dynamic performance and induce additional frequency fluctuations. This paper presents the optimization of Proportional Integral (PI) controller gains in a time-delayed two-area load frequency control (LFC) system with virtual inertia and damping (VID). Optimization techniques such as Crow Search Algorithm (CSA), Particle Swarm Optimization (PSO), Vortex Search Algorithm (VSA), and Sine-Cosine Algorithm (SCA) are used to optimize the PI controller gains to obtain best frequency performance of the system. In all algorithms, the integral square error (ISE) objective function is employed during the optimization process. Results are confirmed via time-domain simulations in Matlab/Simulink.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2023Design and Implementation of a Flyback-Assisted Wide-Range Fully Soft-Switched T-Type Inverter
Ting, Naim Suleyman; Sahin, Yakup; Ozgenel, Mehmet Cihat
A novel soft-switched three-level T-type inverter is proposed in this article. The proposed inverter provides turning-on by zero-voltage transition and turning-off by zero-voltage switching (ZVS) for main switches without any voltage or current stresses. The switching energies are transferred to the snubber capacitors, so the turning-off process of the main switches is improved by these snubber capacitors. Besides, the auxiliary switches are turned on by zero-current switching and turned off by ZVS. Furthermore, all snubber diodes are operated by soft-switching (SS), and the proposed SS snubber cell decreases the electromagnetic interference noises. The novel snubber cell has a simple structure, ease of application, common-ground switches, and low-cost features. The theoretical analysis of the inverter is clarified, and the operating modes for steady-state analysis are presented in detail. The experimental results rated 1-kW output power and 100-kHz switching frequency are provided to justify the theoretical analysis. The proposed unique snubber cell can be easily implemented in other three-level inverters, and the practice is demonstrated in the article.
RDL Kalıcı Kaydıİncele - Conference ObjectYalnız künye2023Heuristic Optimization of PI Controllers for Time-Delayed LFC-EV Systems
Aydin, Ömer; Hasen, Suud Ademnur; Ayasun, Saffet
This study proposes an optimization method for the proportional-integral (PI) controller gains of a single-area time-delayed load frequency control system with electric vehicles (LFC-EV). Four heuristic algorithms are used to optimize the PI controller gains: crow search algorithm (CSA), particle swarm optimization (PSO), vortex search algorithm (VSA), and sine-cosine algorithm (SCA). The integral square error (ISE) objective function is used in the optimization process for all algorithms. Finally, a time-domain simulation of the LFC-EV system is conducted to evaluate the performance of the proposed algorithms. The optimized PI controller gains exhibited superior performance compared to randomly selected gains, leading to decreased oscillations and faster settling times, as evidenced by the results.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2023Investigation of the effect of the gap at the zero-crossing point of PWMs creating the first level voltage in a multi-level inverter
Can, Erol; Sayan, Hasan Hüseyin
The usage of multi-level inverters in converting direct current to alternating current is one of the most demanded and used methods. While creating multi-level voltage with inverters, the operating times of the switches that constitute the first step of the alternating voltage determine the gap of the step at the zero-crossing point. This situation can be preferred to create an extra level. Therefore, this article examines the effect of variation in operating times and frequencies of first-step PWMs on this zero-crossing point. First, the inverter structure providing load voltage is given in the study. Then, the transition of PWM run times is tried for different first-level voltages on the loads. The results obtained show the operation times of PWM at the transition point are quite effective on the load currents and voltages.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2023All-in-one supercapacitors with high performance enabled by Mn/Cu doped ZnO and MXene
Ammar, Ameen Uddin; Bakan-Misirlioglu, Feray; Aleinawi, Mohamad Hasan; Franzo, Giorgia; Condorelli, Guglielmo Guido; Yesilbag, Fatma Nur Tuzluca; Yesilbag, Yasar Ozkan; Mirabella, Salvo; Erdem, Emre
Here, we report the development of high-performance supercapacitor devices using manganese-doped zinc oxide nanowires (Mn-doped ZnO NWs) and copper-doped zinc oxide nanoparticles (Cu-doped ZnO NPs) as a positive electrode with MXene as a negative electrode. Both transition metal (TM)-based electrodes were used separately with MXene, and the performance was tested. When used in combination with MXene as a second electrode, TM-ZnO samples displayed a major increase in the supercapacitors’ performance. The highest-performance supercapacitor recorded values of 151 F/g specific capacitance along with 84 Wh/kg energy density and a power density of 75 kW/kg. Electron paramagnetic resonance and photoluminescence spectroscopy of Mn/Cu-doped ZnO reveals intrinsic and extrinsic defect signals, which were discussed and attributed to the enhancement of the capacitive performance. The presence of the aforementioned defects optimizes the intrinsic properties and boosts the reaction kinetics, thus providing increased electrochemical activity and superior supercapacitor device performance.
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