Mardin Meslek Yüksekokulu

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Citation - WoS: 46
Citation - Scopus: 57
Harmonics Mitigation of Stand-Alone Photovoltaic System Using LC Passive Filter
(Journal of Electrical Engineering and Technology, 2021) Adak, Süleyman
This article investigates modeling and simulation of the off-grid photovoltaic (PV) system, and elimination of harmonic components using an LC passive filter. Pulse width modulation (PWM) inverter is used to convert the direct current to alternating current. It is very important in terms of energy quality that the inverter output current total harmonic distortion (THDI) is below the value given by standards. Harmonic components have negatively effect on off-grid PV power system. THDI should be kept below a certain level in order to prevent damage to the equipment in the off-grid system and to ensure a higher quality energy flow to reduce the total harmonic distortion (THD) of the solar inverter output current; LC passive filter must be connected to the output of the PWM inverter. There are many types of passive filters for solar inverters. One of the most widely used filter types is the LC filter. LC filters are used in off-grid systems. LC filter is smaller in size and lower cost than other filters. But it is more complicated to determine the parameters of the LC filter. Therefore, in order for the system to remain in a steady state, the parameters must be accurately calculated and analyzed. In this study, the output power of the solar inverter, switching frequency, bus voltage etc. values were determined and LC filter parameters were calculated. Since high inductance values are used in LC filters, the voltage drop increases in these filters. To reduce the voltage drop, the DC bus voltage must be increased, which increases the switching losses. LC filter is connected between the inverter and the nonlinear load to filter the harmonic components produced by the DC/DC boost converter, DC/AC inverter and non-linear load. Matlab/Simulink program was used in Simulation and analysis of off-grid solar system. Solar inverter output current THD was measured as 91.55%. After the LC filter is connected to the system, this value has dropped to 2.62%.
Citation - Scopus: 2
Classification of Epilepsy Types from Electroencephalogram Time Series Using Continuous Wavelet Transform Scalogram-Based Convolutional Neural Network
(ASTM International, 2020) Türk, Ömer; Akpolat, Veysi; Varol, Sefer; Aluçlu, Mehmet Ufuk; Özerdem, Mehmet Siraç
During the supervisory activities of the brain, the electrical activities of nerve cell clusters produce oscillations. These complex biopotential oscillations are called electroencephalogram (EEG) signals. Certain diseases, such as epilepsy, can be detected by measuring these signals. Epilepsy is a disease that manifests itself as seizures. These seizures manifest themselves in different characteristics. These different characteristics divide epilepsy seizure types into two main groups: generalized and partial epilepsy. This study aimed to classify different types of epilepsy from EEG signals. For this purpose, a scalogram-based, deep learning approach has been developed. The utilized classification process had the following main steps: the scalogram images were obtained by using the continuous wavelet transform (CWT) method. So, a one-dimension EEG time series was converted to a two-dimensional time-frequency data set in order to extract more features. Then, the increased dimension data set (CWT scalogram images) was applied to the convolutional neural network (CNN) as input patterns for classifying the images. The EEG signals were taken from Dicle University, Neurology Clinic of Medical School. This data consisted of four classes: healthy brain waves, generalized preseizure, generalized seizure, and partial epilepsy brain waves. With the proposed method, the average accuracy performance of three of the EEG records' classes (healthy, generalized preseizure, and generalized seizure), and that of all four classes of EEG records were 90.16 % (± 0.20) and 84.66 % (± 0.48). According to these results, regarding the specific accuracy ratings of the recordings, the healthy EEG records scored 91.29 %, generalized epileptic seizure records were at 96.50 %, partial seizure EEG records scored 89.63 %, and the preseizure EEG records had a 90.44 % rating. The results of the proposed method were compared to the results of both similar studies and conventional methods. As a result, the performance of the proposed method was found to be acceptable.
Citation - WoS: 5
Citation - Scopus: 6
THERMAL ANALYSIS OF DIFFERENT REFUSE DERIVED FUELS SAMPLES
(DoiSerbia, 2021) Ayas, Gizem; Öztop, Hakan F.
As a result of the activities carried out by people to maintain their daily lives in different places such as homes, hospitals, hotels or workplaces, waste consisting of furniture, paint, batteries, food waste, sachets, bottles, fabrics, and fibers with the heterogeneous structure is called municipal solid waste. Secondary fuels with higher heating value, which are generated by recycling of non-recyclable and reusable wastes in municipal solid wastes, are called as refuse derived fuel (RDF). In this study, RDF1 (taken in December, winter season) and RDF2 (taken in June, summer season) samples obtained from different dates were used. The ultimate, proximate, calorific value, X-ray fluorescence, thermogravimetric analysis, and differential scanning calorimetry analysis were performed for these samples. Combustion characterization from RDF samples was investigated in the applied analyzes. The results of the content analysis made were examined separately and compared with the thermogravimetric analysis and differential thermal analysis combustion graph curves. It was revealed that the RDF1 sample had a better combustion compared to the RDF2 sample, as the ash amount and content obtained as a result of the combustion also supported other data. In addition, the results of the analysis show how different the RDF samples taken from the same region in two different months are different from each other.
Citation - WoS: 2
Citation - Scopus: 1
Comparison of near sets by means of a chain of features
(2016) Özcan, A. Fatih; Bağırmaz, Nurettin
If the number of features of objects in a perceptual system, is large, then the objects can be known better and comparable. In this paper basically, we form a chain of feature sets that describe objects and then by means of this chain of feature sets, we investigate the nearness of sets and near sets in a perceptual system
An Applıcatıon Of Exergoeconomic Analysıs For Power Plants
(Vinča Institute of Nuclear Sciences, 2018) Ünal, Fatih
Currently, energy resources are rapidly consumed. Therefore, scientists and engineers study the effective use of energy. In the present study, a thermodynamic and exergoeconomic analysis was performed in a thermal power plant in Turkey. The study involved determining the thermodynamic properties of 27 node points in a thermal power plant unit, and this was followed by calculating energy and exergy values of every node. Mean exergy costs were calculated by establishing energy and exergy balances of the equipment with respect to the calculated results. Subsequently, lost and damaged energies and exergies were calculated, and exergoeconomic factors were determined. The equipments were compared with each other on a graph based on the obtained results. The maximum rate of exergy loss and cost of exergy destruction corresponded to 79.5% and 886,66 $/h, respectively. The maximum exergy losses in a thermal power plant occurred in the boiler, turbine groups, condenser, heating group, pumps, and auxiliary groups. The highest and second highest law efficiencies of the studied thermal power plant corresponded to 32.3% and 28.5%, respectively. The study also involved presenting suggestions for improvement. Additionally, exergoeconomic analyses were conducted while considering the power plants’ investment and equipment maintenance costs. It is expected that the calculation method and the obtained results can be applied to other thermal power plants.
Citation - WoS: 3
Citation - Scopus: 3
Energy Consumption of Defrosting Process in No-Frost Refrigerators
(Yildiz Technical Univ, 2018) Ozkan, D. B.; Unal, F.
Refrigerators have high energy consumption because they consume energy throughout the day, and they are used in all residences and in most offices. Designing more efficient models and, thus, decreasing the energy consumption of refrigerators have become necessary, owing to the global energy scarcity. The purpose of this study was to decrease energy consumption and increase the efficiency of the defrosting process in no-frost refrigerators. The defrosting process plays an important role in the energy consumption of no-frost refrigerators. The amount of energy needed for defrosting and the time it takes are important factors for manufacturers in terms of energy performance. Recently, a theoretical correlation was developed as a function of the frost thickness, heat flux, and frost density for estimating the defrosting time of an evaporator fin surface. The melting time of the frost on the fin was calculated by a mathematical model and compared to results that were obtained experimentally. The results were differed from the actual melting time as 4.7%.
Citation - WoS: 4
Citation - Scopus: 4
Energy and exergy analysis of an industrial corn dryer operated by two different fuels
(International Journal of Exergy, 2021) Ünal, Fatih
In this study, the data obtained after converting an industrial horizontal type corn dryer that meets its drying air temperature from coal to natural gas was compared by thermodynamic analyses. Before starting the drying process, it was assumed that the corn type DKC6050 with 24-25% corn inlet humidity dries when it reaches approximately 14% corn outlet humidity, which is the storage condition after the drying process. Energy and exergy efficiencies, drying rates, unit drying costs, specific moisture extraction rate, and specific energy consumption values of the analysed systems were determined using the data obtained from the experiments carried out at 90, 100 and 110 C drying temperatures. On the other hand, it was also determined that the unit drying cost was approximately 0.1-0.45 €/kg and the specific energy consumption was less than approximately 1,000-8,000 kJ/kgwater. Also, emission values released to the environment were calculated for both systems based on the amount of energy required for drying.
Citation - Scopus: 22
Effects of distributed generations' integration to the distribution networks case study of solar power plant
(İlhami Çolak, 2017) Shobole, Abdulfetah; Baysal, Mustafa; Wadi, Mohammed; Tur, Mehmet Rida
All over the world, the Distributed Generations (DGs) integration to power system has increased in the recent years due to economic, environmental and technical advantages. Turkey which has the huge solar potential has focused on integrating both licensed and unlicensed solar power plants by providing 10 years of purchasing guarantee as an incentive for the electricity producers from solar energy. However, the integration of DGs has several negative effects on the distribution networks (DNs). This work is concerned with investigating the possible challenges that may arise due to integration of PV based DGs on the existing distribution networks. Short circuit current level with respect to variation in MW integration is studied for the case the utility network is weak and strong. When the utility network is strong, the integration effect of inverter based DGs like solar power plants were observed insignificant. However, for the weak utility networks, the integration of inverter based DGs has been observed to have significant influence. Finally, directly integrated DGs (without inverter) are considered to reveal its difference with the non-inverter based DGs. As the case study, the distribution network integration of a solar power project, which is found in the Antalya region of Turkey, is investigated. This is 12 MW solar power plant designed to be connected to the local distribution network in Antalya. It is concluded that the effects of directly integrated DGs are observed more prominent compared to the inverter based DGs. DigSILENT Power Factory simulation tool is used for the study.

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