Search

Background/aim It is known that the presence of fragmented QRS (fQRS) on electrocardiography (ECG) is associated with cardiovascular events. The aim of this study was the evaluation of fQRS formation and its relationship with the left ventricular hypertrophy (LVH) parameters in acromegaly patients. Materials and methods In total, 47 previously diagnosed with non-hypertensive acromegaly patients and 48 control subjects were included in the study. ECG and transthoracic echocardiography (TTE) were performed for each participant. Acromegaly patients were divided into two groups according to the fQRS formation on the ECG. Left ventricular wall thicknesses, and left atrial diameter (LAD), left ventricular mass (LVM), left ventricular mass index (LVMi), and relative wall thickness (RWT) were obtained. Results In control group 5 (10.4%) and in acromegaly group 17 (36.2%) patients had fQRS on ECG (p = 0.003). LAD [36.0 (34.0–38.0) vs. 38.0 (35.0–41.0) mm, p < 0.001], LVM [155.27 ± 27.00 vs. 173.0 (153.0–235.0) g, p < 0.001], LVMi [83.12 ± 13.19 vs. 92.0 (83.0–118.0) g/m², p < 0.001] and RWT [0.39 ± 0.03 vs. 0.43 (0.41–0.45), p = 0.001] were significantly higher in patients with acromegaly. Disease duration was significantly higher (11.59 ± 1.3 vs. 8.2 ± 1.8 years, p < 0.001) in the fQRS (+) group. LAD [41.0 (39.0–42.5) vs. 37.0 (34.7–38.0) mm, p < 0.001], LVM [219.0 (160.5–254.5) vs. 164.0 (153.0–188.0) g, p = 0.017], LVMi [117.0 (92.5–128.5) vs. 86.0 (82.0–100.2) g/m², p = 0.013] and RWT [0.44 (0.42–0.49) vs. 0.43 (0.40–0.44), p = 0.037] were significantly higher in fQSR (+) acromegaly patients. In multivariate logistic regression analysis, disease duration (odds ratio: 10.05, 95% CI: 1.099–92.012, p = 0.041) and LAD (odds ratio: 2.19, 95% CI: 1.030–4.660, p = 0.042) were found to be the independent predictors of fQRS formation. Conclusion The results of our study revealed that fQRS (+) acromegaly patients had increased LVH parameters compared to fQRS (-) patients.

Finding the equivalent circuit parameters for photovoltaic (PV) cells is crucial as they are used in the modeling and analysis of PV arrays. PV cells are made of silicon semiconductor materials. These materials have a nonlinear characteristic. This distorts the sinusoidal waveform of the current and voltage. As a result, harmonic components are formed in the solar system. The PV cell is the smallest building block of the PV system and produces voltages between 0.5V and 0.7V. It serves as a source of current in the solar system. The amount of radiation hitting the cell determines how much current it produces. In an ideal case, a diode and a parallel current source make up the equivalent circuit of the PV cell. In practice, the addition of a series and parallel resistor is made to the ideal equivalent circuit. There are many equivalent circuits in the literature on modeling the equivalent circuit of a PV cell. The PV cell single diode model is the most used model due to its ease of analysis. In this study, the iterative method by Newton-Raphson was used to find the equivalent circuit parameters of a PV cell. This method is one of the most widely used methods for determining the roots of nonlinear equations in numerical analysis. In this study, five unknown parameters (Iph, Io, Rs, Rsh, m) of the PV cell equivalent circuit were quickly discovered with the software program prepared based on the Newton-Raphson method in Matlab.

This paper deals with modeling and simulation of the total harmonic distortion of the current (THDI) dispatched from the inverter and connected to nonlinear load. The change of THDI was examined in relation to the ambient temperature (T) and solar irradiance (G).The developed model is being used to extract parameters for a given THDI as a function of temperature and solar radiation. This study outlines the working principle of photovoltaic (PV) panel as well as PV array. Off-grid PV system is modeled by using Matlab/Simulink program, and detailed analytical study has been carried out in this work. The design, modeling and simulation of this study are performed from 50 up to 988 W/m2 for solar irradiance. Harmonic components have negative effects on the steady-voltage stability of the PV system. Therefore, analytical expression is needed for steady-state stability analysis in order to reduce negative effects. Hence, two analytical expressions of THDI were obtained by two new different methods which are statistical package for the social sciences program and genetic expression programming. Eventually, two different methods have been verified by the Matlab/Simulink program in order to find out THDI and demonstrated the effectiveness of the proposed strategy. As a result of this study, it is observed that input current THDI of nonlinear load is too high at low irradiance. It is suggested that active harmonic filters should be used at low irradiance in order to produce better quality energy and avoid damages in the PV system. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.

An elevation in blood pressure (BP) during exercise is the normal physiological response, however an abnormally exaggerated rise in BP, in terms of hypertensive response to exercise (HRE), is seen as a prognostic factor for end-organ damage and mortality. HRE is more common in hypertensive (HT) patients and data are lacking on the effect of antihypertensive medication on HRE. In this study, we evaluated patients who underwent treadmill exercise testing (TET) to reveal the effect of antihypertensive medication on HRE.A cohort of 2970 individuals underwent TET and data were evaluated for HRE development. HRE has been defined as a systolic BP210 mmHg in males and190 mmHg in females throughout the TET. To reveal the effects of antihypertensive medication on HRE, 992 HT patients were analyzed.HRE was observed in 11.4% (HRE was associated with gender, BMI and beta-blocker use in hypertensive with male gender and higher BMI associated with higher HRE, while beta-blocker-based treatment, either mono- or combination therapy, associated with lower HRE.

Güç sistemlerinde kararlılık, sistemin herhangi bir bozucu etkiye maruz kaldığı durumda ve bu etkiden sonra senkron generatörün senkronizmayı koruyabilme yeteneğidir. Güç sisteminde bu tür etkiler çok sık görülmektedir. Bu nedenle sürekli hal kararlılığı sistemin analizi ve sentezi bakımından önem taşımaktadır. Bu çalışmada güç santrallerinde fotovoltaik enerji sistemlerinin kararlılığa etkisini görmek için iki farklı durum incelenmiştir. İlk durumda dağıtım şebekesinin bağlı olduğu sistemde üretim elemanı olarak şebekenin yanında senkron generatör bulunmaktadır. İkinci durumda ise dağıtım şebekesi ve generatöre ilaveten güneş panelleri gurubu da sisteme ilave edilmiştir. Böylece fotovoltaiklerin kararlılık üzerine etkisi incelenmiş ve sistemin kararlılık analizi yapılmıştır. Sistemin arıza oluştuğu sırada kararlı olup olmadığı ve kararsızlık durumundaki değişimler incelenmiştir.

Fotovoltaik (PV) sistemlerin cikis gucu, gunes isinimi ve sicaklik ile ilgilidir. Bu makalede, PV sisteminin cikis gucunun sicaklik ve gunes isinimina bagli degisimi incelenmistir. Ayrica, bu calismada PV panellerinin yaninda PV dizininin calisma prensibi ozetlemistir. Off-grid PV sistemi Matlab/simulasyon programi kullanilarak modellenmis ve bu calismada detayli calismasi gerceklestirilmistir. Ayrica, farkli sicaklik ve isinim degerleri icin PV sisteminin cikis gucu analiz edilmistir. Sonuc olarak, PV sisteminin cikis gucunun analitik ifadesi, Sosyal Bilimler Icin Istatistik Programi (SPSS) kullanilarak bulunmustur.

Bilgi insanın var olduğu günden sürekli birçok iletişim yöntemi ve bilimsel alanla etkileşim içerisine girmiştir. İnsanların bilgiyi paylaşma ihtiyacının artmasıyla, bilgi içeriğinin daha iyi anlaşılması için çok çeşitli görselleştirme yöntemleri uygulanmaya başlanmıştır. Bilgi aktarımının teknoloji, bilim, sanat ve kültür alanının genişlemesine paralel olarak gelişmesi sonucu uygulanmaya başlanan bu yöntemler bundan sonra ki süreçte de gelişmeye devam edecektir. Günümüzde bilgi, bilgilendirme tasarımının önemli bir kolu olan veri görselleştirmesiyle kendini ifade edebilmekte ve içeriğin iletilebilmesine önemli ölçüde olanak sağlamaktadır. Bu çalışmada “Veri Görselleştirmesi ve Bilgilendirme Grafikleri”nin, bilgilendirme amacına yönelik bilimsel katkısı ele alınmaktadır. Bu kapsamda bir veri görselleştirme aracı olarak yazının tanımı ve tarihsel oluşum süreci incelenmiş olup insanların geçmişten günümüze bilgi aktarmada kullandıkları veri görselleştirme yöntemlerinin tanımı, tarihsel süreç içerisindeki rolü, günümüze kadar değişen ve gelişen görselleştirme konuları ele alınmıştır. Bu konunun öncüleri ve ustaları örnek çalışmalarıyla birlikte incelenmiştir.Bununla birlikte, konunun temel ilke ve esaslarına yer verilerek ve konu bir tasarım disiplini içerisinde ele alınarak bilgilendirme tasarımıyla olan ilişkisi değerlendirilmiştir. Ayrıca, tasarımcının içerik ve estetik arasındaki dengeyi koruyarak anlaşılır bir görselleştirme oluşturma çabası içine girilmiştir. Son olarak, veri görselleştirmesinin güncel konumuna göre tasarım sürecindeki yöntem ve uygulamaları incelenerek uygulama alanları, günümüzdeki farklı ortamlarla olan bağı üzerinden değerlendirilerek örneklerle pekiştirilmiştir.

Contrast-induced nephropathy (CIN) is associated with worse prognosis in patients with acute coronary syndrome (ACS). Early identification and intervention for patients with a high risk of CIN are very important to improve clinical outcomes. Inflammation plays important role in the development of CIN in the setting of ACS. The monocyte to high-density lipoprotein ratio (MHR) is a novel inflammatory marker. Bleeding is also associated with worse prognosis in such patients. We aimed to investigate whether the preprocedural MHR had a predictive role for CIN development in such patients. In addition, using the thrombolysis in myocardial infarction classification, we aimed to assess whether there was any relationship between bleeding and CIN. A total of 647 patients (496 males; age: 63.3 ± 12.7 years) with ACS who underwent percutaneous coronary intervention (PCI) were included in the study. Seventy patients (10.8%) had developed CIN. Age, diabetes mellitus, contrast volume, estimated glomerular filtration rate, and MHR were independent predictors for CIN. Preprocedural MHR may be used as a simple marker of CIN. It may help with the early identification of patients with ACS who underwent PCI who are at high risk of CIN thus allowing the planning of protective measures.

Guc sistemlerinde kararlilik, bozucu bir etkiye maruz kaldigi durumda ve bu etkiden sonra senkron generatorun senkronizmayi koruyabilme yetenegidir. Bu bozucu etkiye ornek olarak enerji iletim hatlarindaki buyuk yuk degisimi, acma-kapama durumlari verilebilir. Guc sistemlerinde bu tur etkiler cok sik gorulmektedir. Bu yuzden surekli hal kararliligi sistemin analizi ve sentezi bakimindan onemlidir. Bu calismada dagitim sebekesine bagli senkron generator guc acisi, hizi(rpm), aktif gucu, akim ve gerilim degerleri incelenmis ve ariza kararlilik analizi yapilmistir. Sistemin ariza olustugu zamanda kararli olup olmadigi incelenmis ve kararsizlik durumunda generator guc acisi ve aktif gucunun degisimleri incelenmistir.

Renewable energy sources are important in the green building for energy saving. The use of renewable energy sources needs energy management in hbyrid green buildings. By using an energy management system, the energy costs of hyrid green buildings can be systematically and regularly controlled. In other words, it provides each consumer to produce their own energy in their own building, and reduce the dependence to the central power grid. Besides, the change of electricity pricing according to hours can be seen as another parameter. The aim of this study is to develop an energy informatics application for energy management in green buildings. Resource management scenarious have been created according to regional atmospherical conditions. These scenarious were monitored via an energy source management interface. In this study, a software which have a visual interface was developed. This software conducts an energy management system for a hybrid green building which has three kinds of energy resource like utility, solar arrays and energy storage system. This software proposes an resource management system between these three types of resources.Proposed system depends on some scenarious which are interchangable according to external parameters such as; variability of the price of energy received from electric grid, seasonal factors, fullness level of the batteries were designed. In the scenarios of the electric loads, making them continuous and as cheap as possible were taken into consideration. With the developed software, it is aimed to monitor energy consumption of each scenario. Thus, an arrangement using cheap, continuous and environmentally friendly resources as possible as will be provided.

This paper is regarding the design, modeling and simulation for reducing harmonics with passive LLCL filter in off-grid solar system. It is desired that current and voltage waveforms are to be in the sinusoidal form during energy generation from stand-alone solar systems. This condition can be provided by the most important one of the main factors which to determine the quality of electrical energy. Due to the harmonics produced by the non-linear loads, the waveform of the current and voltage is distorted from the sinusoidal form. The passive LLCL filter is designed and analyzed for mitigation of the total harmonic distortion for current (THDI) in the proposed off-grid PV system. The passive LLCL filter is practically installed between solar inverter and non-linear load. Simulation results are in a good compliance with the theoretical analysis. This study describes a design methodology of a LLCL filter for off-grid power system with a comprehensive study of how to mitigate the harmonics in off-grid solar system. The using of a LLCL filter mitigates the THDI that injected by a six pulse rectifier which is used as a non-linear load. The simulation result shows that the reduction of THDI from 89.89% to 3.257%. This paper attempts to show that the using of LLCL filter with a stand-alone solar system can highly improve the power quality of the system.

A PCB machine that can draw trace lines and drill holes on a PCB card is developed. The machine consists of a computer, a driving circuit and a mechanical setup. The overall system is operated and controlled from a computer through a program written in Matlab. A relay based driving circuit is developed to perform operations onto the mechanical setup. A communication protocol is established between the computer and the driving circuit through LPT1 port. In this initial work, we demonstrate that the machine successfully draws a trace line and drill holes on two pads which are at both ends of the line. Currently the machine is used only for educational purposes at our lab., Bu çalışmada PCB karları üzerine yolları oluşturabilen ve pad'lerin orta noktalarına delik delebilen bir cihaz geliştirilmiştir. Cihaz bir bilgisayar, bir sürücü devresi ve bir mekanik aksamdan oluşmaktadır. Sistemin tümü Matlab'te yazılan bir program tarafından kontrol edilmektedir. Mekanik aksam üzerinde yaptırılacak hareketlerin kontrolü röleler kullanılarak geliştirlen bir elektronik devre ile yapılmaktadır. Bilgisayar ile sürücü devresi arasındaki haberleşme protokolü bilgisayarın LPT1 portundan gerçekleştirilmiştir. Bu ilk çalışmamızda cihazımızın başarılı bir şekilde bir PCB kartı üzerine bir adet yol çizdiğini ve yolun her iki tarafında bulunan padlerin orta noktalarına birer delik deldiğini göstermekteyiz. Şu anda cihazımız sadece eğitim amaçlı olarak labaratuarımızda kullanılmaktadır.

Determination and investigation of incidents affecting Power Quality (PQ) is very important for consumers. In this study, estimation of PQ events is obtained to determine the disturbances of PQ by using Empirical Wavelet Transform (EWT) and Discrete Wavelet Transform (DWT) methods and with this estimated parameters. PQ disturbances were examined with Support Vector Machine (SVM), Artificial Neural Network (ANN) and Adaptive Neuro-Fuzzy Inference System (ANFIS) classification methods. Voltage signals (sag, swell, interruption, transient and normal) used in the classification of PQ disturbances were recorded from grid with the aid of a microcontroller based on device designed with a sampling frequency of 6.4 kHz. Classification consequences using Machine Learning Methods show that DWT outperforms over EWT for feature extraction processing and the classification accuracy is tabled. Classification by ANN and ANFIS through the use of conjecture parameters in PQ disturbances based on DWT Method has been recommended.

The increase in the use of renewable energy systems in recent years has led to an increase in the importance of work on micro-grids. In micro-grids, energy is consumed where it is produced. This leads to a reduction in transmission and power losses in the lines. At the same time, the negative effects of the industrial plants that disrupt the quality of power are eliminated by the micro-grid model and more efficient and reliable grids can be established. Technological developments that impact each field have also affected the electricity distribution grids. Problems such as inefficient energy transmission systems caused by high power losses, problems in the integration of renewable sources into the grid, inflexible demand, and wage problems make it difficult to meet the increasing demand with the traditional structure. In this study, a smart grid system was set up in the sample micro structure. The system consist from a photovoltaic system with a consumer and a grid system that feeds this consumer. There are a photovoltaic system and also a battery group in the applied micro grid. The power of the photovoltaic system in the micro-grid is continuously monitored by a microcontroller. The energy level information of PV panel system, the battery, and grid are supplied by voltage divider circuits to microcontroller. The information transmitted by the voltage dividers to the microcontroller is evaluated by the control algorithm. Considering account possible possibilities, the receiver is primarily fed by the photovoltaic system, in other cases fed from the grid or the battery system, thanks to the semiconductor switches used in the microcontroller control. In addition, excess energy generated by the microcontroller is transferred to the main grid. As a result of this application, the level of use of the renewable energy system has been increased and the energy cost has been reduced.

Increased energycost is important for industrial users. To reduce energy cost in industry, theestablishment of systems that produce their own energy financially relieves theusers. Studies on PV systems have focused on the importance of renewable energysources. In this study, cost analysis and shipment duration account is realizedfor demanding the factory energy need with PV system and cogeneration bydisabling utility. Moreover,by drawing single–line diagram of the factory, in case ofpossible error the stability of system are analyzed. According to cost analysisresults and the resulting graphs, it is debated whether this investment ispositive or not., Artanenerji maliyetleri endüstriyel kullanıcılar için önem arz etmektedir.Endüstride enerji maliyetini düşürmek için kendi enerjisini üreten sistemlerinkurulması kullanıcıyı maddi açıdan rahatlatmaktadır. Yenilenebilir enerjikaynaklarının önem kazanmasıyla PV sistemler üzerinde çalışmalaryoğunlaşmıştır. Bu amaçla bu çalışmada, bir fabrikanın elektrik enerjisiihtiyacını şebekeyi devre dışı bırakarak fotovoltaik (PV) sistem vekojenerasyon ile sağlamak amacıyla bir maliyet analizi ve amortisman süresihesabı gerçekleştirilmiştir. Ayrıca fabrikanın tek hat şeması çizilerek olasıbir hata durumunda sistemin kararlılık analizi hakkında çıkarım yapılmıştır.Elde edilen grafikler ve maliyet analizi sonucuna göre yapılan bu yatırımınolumlu olup olmadığı tartışılmıştır.

Son yıllardaenerji kalitesinin önemi artmaktadır. Bu çalışmada, bu faktöre olumsuz etkileriolan harmonikler ele alınmıştır. Harmoniklerin genel tanımlamaları yapılarakbunların enerji sistemi üzerindeki etkileri incelenmiştir. Bu amaçla birtekstil fabrikasında tüketilen enerji kalitesi ve harmonik ölçümü incelenmiştir.Kullanılan dokuma tezgâhı motorları ve invertörler dağıtım şebekesini olumsuzyönde etkilemektedir. Bu etkiler güç kalitesini ve sistemin verimidüşürmektedir. Bu çalışma ile belirlenen tekstil fabrikasında çeşitli güçkalitesi parametreleri için gerekli ölçümler yapılmıştır. Yapılan analizlersonucunda kompanzasyon sisteminin harmonik oluşumunu etkilediği ve akım-gerilimdalga şeklinde bozukluklar meydana getirdiği gözlenmiştir. Şebekede oluşan buharmoniklerin etkisinin azaltılması için harmonikli kompanzasyon sistemininmeydana gelen güç kalitesi sorunlarını çözeceği düşünülmektedir., In recent years,the importance of power quality has been increasing. In this study, theharmonics with negative effects on these factor are considered. The effect onenergy system are analyzed by making general definitions of harmonics. For thispurpose, harmonic measurement and energy quality consumed in the textilefactory are analyzed. Used weaving loom motors and inverters negatively affectthe distribution network. These effects decrease the power quality andefficiency of system. With this study required measurements were made for powerquality parameters. As a result of commited analysis, compensation systemaffects harmonic formation and causes current-voltage waveforms irregularity. Toreduce the effects of these harmonics, it is considered that harmoniccompensation system will be solved the power quality problems.

An efficient converter topology for extracting maximum power from a photovoltaic module is presented in this paper. The proposed topology is implemented on a stand-alone battery charging system. A reversed buck-boost converter enabling parallel power processing (PPP) with a power switch referenced to the common return is the core of the charging system. Small-signal analysis of the proposed charging system is carried out to facilitate the design of a compensator for maximum power point (MPP) tracking. The simulation and experimental results confirm the validity of the model and verify the high efficient operation while tracking the MPP. The use of the PPP with split loads is also presented which would improve the converter size, efficiency, and step-down duty ratio.

Because of developing technology, the usage of new electr onic devices is rising at the people's casual and working life. T he distribution network is affected negatively due to the used devices' different structure and working basis. Paticularly, pow er electronics equipment impres the distribution network negativ ely. Owing to these effects, power quality parameters are exceeded determined standard s for distribution networks. This situation affects the power quality and efficiency. In this study, n ecessary measurement and analyses are made for power quality paramet er at the medical, office and residental - density network. At the conclusion of analyses; it is observed that the loads which are medical, office and residental - density form harmonics excessively and damage the current wave shape over the distribution netwo rk. The network type which is received measurement is TT type. With the passive filter usage for harmonics that is formed at the network, is predicted to solution of power quality problems., Gelişen teknoloji ile birlikte insanların günlük ve iş hayatlarında yeni elektronik cihazların kullanımı da artmaktadır. Kullanılan bu cihazlar farklı yapıları ve çalışma temellerinden dolayı dağıtım şebekesini olumsuz yönde etkilemektedir. Özellikle güç elektroniği esaslı elemanlar şebekeler üzerinde olumsuz yönde etki yapmaktadır. Bu etkiler güç kalite parametrelerini, dağıtım şebekesi için belirlenen standartlar dışına çıkartmaktadır. Bu da güç kalitesini ve verimini etkilemektedir. Bu çalışma ile belirlenen medikal, ofis ve konut yoğunluklu şebekelerde çeşitli güç kalitesi parametreleri için gerekli ölçümler yapılarak analiz edilmiştir. Yapılan analizler sonucunda medikal, ofis ve konut ağırlıklı yüklerin dağıtım şebekesi üzerinde çok fazla harmonik oluşturduğu ve akım dalga şeklini bozduğu gözlenmiştir. Ölçüm yapılan dağıtım şebekelerinin yapısı TT şebeke tipidir. Şebekede oluşan harmonikler için ise pasif filtre kullanılmasının meydana gelen güç kalite sorunlarının çözümünü düşünülmektedir.

In this study, a new approach based on an adaptive neuro-fuzzy inference system (ANFIS) was presented for the prediction of early heat of hydration of plain and blended cements. Two different type of model is trained and tested using these data. The data used in these models are arranged in a format of five input parameters that cover the additives percentage (AP), grinding type (GT) and finesses of cements (FC) and an output parameter which is heat of hydration of cements (HHC). The results showed that neuro-fuzzy models have strong potential as a feasible tool for evaluation of the effect of additives percentage, grinding type (GT) and finesses of cements on the early heat of hydration of cements. Some conclusions concerning the impacts of features on the prediction of early heat of hydration of plain and blended cements were obtained through analysis of the ANFIS. The results are highly promising, and a comparative analysis suggests that the proposed modelling approach outperforms ANN model in terms of training performances and prediction accuracies. The results show that the proposed ANFIS model can be used in the prediction of early heat of hydration of plain and blended cements.

Managing electrical energy supply is a complex task. The most important part of electric utility resource planning is forecasting of the future load demand in the regional or national service area. This is usually achieved by constructing models on relative information, such as climate and previous load demand data. In this paper, a genetic programming approach is proposed to forecast long term electrical power consumption in the area covered by a utility situated in the southeast of Turkey. The empirical results demonstrate successful load forecast with a low error rate.

Photovoltaic (PV) systems produce a significant amount of electrical energy used around the world. The performance of a PV array is affected by temperature, solar insolation, shading and array configuration. Obtainable maximum power generation from PV based energy production systems is only possible with Maximum Power Point Tracking (MPPT) methods. In order to maximize the efficiency of PV energy conversion systems, solar panels and arrays should be operated at maximum power points. At maximum power point, solar arrays generate the electric energy at maximum efficiency and minimum losses. This paper discusses the following issues: (1) what is the effect of MPPT unit in PV systems, (2) two connection methods between solar arrays and buck-boost DC/DC converter with MPPT unit, (3) determine behaviours of PV power generation systems in cloudy and sunny conditions. DOI: http://dx.doi.org/10.5755/j01.eee.21.6.13761

Fotovoltaik sistemlerin elektrik şebekelerine paralel bağlanması son yıllarda araştırma konusu olarak öne çıkmaktadır. Güç elektroniği tabanlı dönüştürücülerin paralel bağlanmada kullanılması sonucunda kararlılık ve güç kalitesi açısından problemlerin oluştuğu görülmektedir. Özellikle mikro şebekelere bağlı fotovoltaik enerji kaynaklarının devreye giriş çıkışlarındaki olası düzensizlikler, şebekeye sürekli enerji sağlanmasında süreklilik, kararlılık ve kalite açısından bir takım sorunlar literatürde vurgulanmıştır. Bu tez çalışmasında mikro şebekeye H5 tipi evirici üzerinden paralel bağlı bir fotovoltaik kaynak ve şebekenin simulinkte modellemesi gerçekleştirilecektir. Maksimum güç takip algoritmaları uygulanacaktır. Bunun yanında PWM ile evirici kontrolü de gerçekleştirilecektir. Öncelikli olarak meydana gelebilecek problemler gözlenecektir. Daha sonra bu problemler için çözüm önerileri geliştirilecektir. Çözüm önerilerinin uygunluğu bilgisayar benzetimleri ile gösterilecektir., Yenilenebilir enerji üretim sistemlerinin elektrik şebekelerine bağlanması son yıllarda ciddi bir artış göstermektedir. Toplam enerji üretimi içindeki payları son yıllarda artmaktadırlar. Bunun en önemli nedeni ise ucuz ve çevre dostu olmalarıdır. Bununla birlikte şebekeye bağlantı sırasında bir takım problemler öne çıkmaktadır. Bağlantılarda yarıiletken dönüştürücülerin kullanımı zorunlu olduğundan bir takım kontrol ve uygulama problemi ortaya çıkmaktadır. Bu çalışmada şebekeye bağlantılı sistemlerde kullanılan H5 tipi evirici ile yükselten tip kıyıcılarda maksimum güç noktası ve histerisis kontrollerinin uygulanması incelenmiştir. Yapılan bilgisayar benzetimlerinde çeşitli karşılaştırmalar da sunulmuştur. Ayrıca iki farklı topoloji incelenmiştir. Merkezi ve yerel olmak üzere iki tür toplojoide güç ve verim analizleri gerçekleştirilmiştir

A primary goal of an industrial electric power system is to minimize production losses in industrial facilities maintaining the industrial process running after the occurrence of certain supply disturbances. The automatic motor restarting is one of the strategies used in the industrial facilities, especially in Oil and Gas facilities, in order to achieve this goal. Aim of this strategy is to allow that after a voltage dip or disturbance, the medium voltage and low voltage motors will be automatically reenergized within predetermined time and in a certain order when voltage is restored. These abnormal voltage conditions may be caused by cleared short-circuits upstream, generation and public supply voltage outages or a simple automatic transfer system of a selective secondary substation operation. This paper presents the automatic motor restarting scheme applied at a large oil refinery where more than 600 motors are assigned to automatic restarting. Application criteria for motor restarting, power system simulations and physical implementation of this scheme are discussed in this paper.

Solar energy is a renewable energy source and occupies an important position in power generation. While it is environment-friendly, silent and non-fuelled, its high investment costs and low efficiency in terms of energy conversion bring about various disadvantages. Therefore, studies on the improvement of systems operated via photovoltaic energy gained importance and the researches and developments within the field of current power conversion systems enabled the photovoltaic systems to gain momentum. Maximum power point tracking (MPPT) must be used to obtain maximum performance from the solar energy system. In this study, Perturb and Observe (P&O) algorithm -the most commonly used algorithm in MPPT systems- was analyzed, an approach towards eliminating oscillation problems, improving speed to obtain more power value, were maintained and reference current value was obtained from P&O algorithm under changing and constant PV panel radiation conditions. Finally, the proposed P&O algorithm was simulated and the results are discussed.

ÖzetGüç kalitesi olayları içinde, özellikle dağıtım şebekeleri içinde, en çok karşılaşılan problemlerin başında harmonikler gelir. Doğrusal olmayan yük karakteristikleri harmonik oluşumunun en önemli kaynağıdır. Harmonik bozulmalarının ölçülmesinde toplam harmonik bozulma (THB) parametresi kullanılır. Bu parametre sinyaldeki kirlenmenin göstergesidir. Bunun yanında gerek frekans ve gerekse zaman- frekans düzleminde pek çok yöntem kullanılagelmiştir. Bu çalışmada Ayrık Hartley Dönüşümü (AHD) ile harnonik analizi ve THB hesaplaması yapılmıştır. Kaydedilmiş ve simüle edilmiş örnek dalga şekillerinin içerdiği temel bileşenin tam katı harmonikler analiz edilmiştir. Ayrıca zaman-frekans düzleminde analizler yapılmıştır. Yapılan analizlerin sonuçları AFD ile karşılaştırılmış ve AHD’nin AFD kadar doğru sonuç verdiği görülmüştür. Sonuç olarak, AHD’nin AFD kadar başarılı olduğu ve kullanıma uygun olduğu görülmüştür. Anahtar Kelimeler: Ayrık Hartley Dönüşümü, Güç Kalitesi, Harmonik Bozunum, Güç kalitesi olayları içinde, özellikle dağıtım şebekeleri içinde, en çok karşılaşılan problemlerin başında harmonikler gelir. Doğrusal olmayan yük karakteristikleri harmonik oluşumunun en önemli kaynağıdır. Harmonik bozulmalarının ölçülmesinde toplam harmonik bozulma (THB) parametresi kullanılır. Bu parametre sinyaldeki kirlenmenin göstergesidir. Bunun yanında gerek frekans ve gerekse zaman- frekans düzleminde pek çok yöntem kullanılagelmiştir. Bu çalışmada Ayrık Hartley Dönüşümü (AHD) ile harnonik analizi ve THB hesaplaması yapılmıştır. Kaydedilmiş ve simüle edilmiş örnek dalga şekillerinin içerdiği temel bileşenin tam katı harmonikler analiz edilmiştir. Ayrıca zaman-frekans düzleminde analizler yapılmıştır. Yapılan analizlerin sonuçları AFD ile karşılaştırılmış ve AHD’nin AFD kadar doğru sonuç verdiği görülmüştür. Sonuç olarak, AHD’nin AFD kadar başarılı olduğu ve kullanıma uygun olduğu görülmüştür

Artis gosteren kisisel ve is yasamindaki enerji tuketimine bagli olarak, batarya sektorunde daha gelismis teknolojilerin ortaya cikmasina ihtiyac duyulmaktadir. Bu noktada oncelikli olarak bir bataryadan beklenen, ihtiyac duyulan enerjiyi, ihtiyac duyulan zaman suresince saglamasidir. Bunun yaninda sarj doluluk durumu bilgisinin dogru ve kesin olarak bilinmesi de batarya yonetim sisteminin en onemli unsurlarindan biridir. Bu calismada, lityum-ion (Li-Ion) aku yonetim sisteminin en onemli unsurlarindan birisi olan batarya doluluk durumunu icin genetik ifade programlama algoritmasi ile kestirimi incelenmistir. Kestirim calismasinda giris degerleri olarak atanan batarya akimi, batarya cikis voltaji ve zaman degiskenleri ile cikis degeri olarak batarya turlerine ozel sarj doluluk durumu verileri elde edilmistir. Lityum-Ion akuler icin matematiksel desarj denklemleri olusturulmus ve boylece pil turune ozel desarj bilgileriyle daha dogru ve kesin SOC tahmini yapilabilmesi amaclanmistir.

A parallel power conversion based fast battery charger topology for electric vehicles is presented in this study. The proposed topology has high system efficiency as well as reduced converter size. The proposed topology also provides wider range of duty ratio compared to conventional topologies. The enhancements of the proposed topology are evaluated and the results are demonstrated through an example design.

8th Biennial Meeting of the International Work-Conference on Artificial Neural Networks -- JUN 08-10, 2005 -- Vilanova, SPAIN, WOS: 000230384000136, This paper proposes a new controller based on neural network and fuzzy logic technologies for load frequency control to allow for the incorporation of both heuristics and deep knowledge to exploit the best characteristics of each. A "Dynamical Fuzzy Network (DFN)" that contains dynamical elements such as delayers or integrators in their processing units is used in the adaptive controller design for load frequency control. A DFN is connected between the two area power systems. The input signals of the DFN are the ACEs and their changes. The outputs of the DFN are the control signals for the two area load frequency control. Adaptation is based on adjusting parameters of DFN for load frequency control. This is done by minimizing the cost functional of load frequency errors. The cost gradients with respect to the network parameters are calculated by adjoint sensitivity. In this paper, it is illustrated that this control approach is more successful than conventional integral controller for load frequency control in two area systems., Univ Politecn Catalunya, Univ Granada, Univ Malaga, Spanish Minist Educ & Ciencia, City Council Vilanova