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Öğe Dynamic Characteristics Analysis of DC-DC Converter for Server Using Digital Current-Frequency Detector(IEEE, 2016) Furukawa, Yudai; Nibu, Shintaro; Maruta, Hidenori; FujioKurokawa; Hirose, Keiichi; Colak, IlhamiThe purpose of this paper is to analyze the dynamic characteristics of proposed digital peak current mode dc-dc converter. The waveforms of the output voltage and the reactor current are derived by the small signal analysis. They are compared with simulation results assuming an actual large amplitude operation. It is confirmed that the tendency of the transient response is indicated based on the analysis results. The experimental result of the proposed method shows the validity of the proposed method and a gradual response is obtained by an improvement of the stability of dc-dc converter. Consequently, the proposed method can be a solution of implementing the peak current mode control in digital.Öğe Dynamic characteristics of integral gain changeable digital control dc-dc converter for suppression of output capacitance(International Journal of Renewable Energy Research, 2016) Kajiwara, Kazuhiro; Tajima, Hidenobu; Maruta, Hidenori; Kurokawa, Fujio; Colak, IlhamiStability of power converters has become more and more important in hybrid green energy systems because of its difficulties to maintain a stable dc-bus. This paper presents dynamic characteristics of a digital integral gain changeable control dc-dc converter to realize high stability with suppression of the output capacitance. The integral gain changeable control method uses a variable integral gain, which is changed by the value of load current. The stability analysis is conducted by Bode diagrams. It is shown that the transient response and stability of the integral gain changeable method are better than the conventional fixed integral gain control method even if the output capacitance is smaller than the conventional method. Simulation and experimental results show the effectiveness of our concept.Öğe Dynamic Characteristics of Integral Gain Changeable Digital Control DC-DC Converter for Suppression of Output Capacitance(Int Journal Renewable Energy Research, 2016) Kajiwara, Kazuhiro; Tajima, Hidenobu; Maruta, Hidenori; Kurokawa, Fujio; Colak, IlhamiStability of power converters has become more and more important in hybrid green energy systems because of its difficulties to maintain a stable dc-bus. This paper presents dynamic characteristics of a digital integral gain changeable control dc-dc converter to realize high stability with suppression of the output capacitance. The integral gain changeable control method uses a variable integral gain, which is changed by the value of load current. The stability analysis is conducted by Bode diagrams. It is shown that the transient response and stability of the integral gain changeable method are better than the conventional fixed integral gain control method even if the output capacitance is smaller than the conventional method. Simulation and experimental results show the effectiveness of our concept.Öğe Enhanced Operating Scheme of ESS for DC Transit System(IEEE, 2016) Kwon, Kyoungmin; Lee, Kyoung-Gu; Kim, Taesuk; Lee, Jinkook; Jone, Byoung-Jeen; Choi, Jaeho; Colak, IlhamiThe energy storage system (ESS) used in the DC feeding urban railway system is an equipment that recycles the regenerated energy produced by the railway vehicles as well stabilizing the catenary voltage. This paper proposes an operation algorithm of ESS that allows a more effective use of the equipment. The proposed algorithm includes an advanced line voltage tracker (ALVT), which responds to the fluctuating catenary voltage by tracking it and the supercapacitor voltage tracker (SCVT), which modifies the operating voltage of the supercapacitors to increase the receptivity of power constrained by the rated current of supercapacitors. The feasibility of this algorithm has been tested and verified at the Seocho substation in Seoul Metropolitan Rapid Transit (SMRT) Line.Öğe Improved Performance and Power Quality of Direct Torque Control of Asynchronous Motor by Using Intelligent Controllers(Taylor & Francis Inc, 2016) Aissa, Oualid; Moulahoum, Samir; Colak, Ilhami; Kabache, Nadir; Babes, BadreddineDirect torque control of asynchronous motors has good dynamic performance of torque and flux. However, the use of hysteresis controllers leads to a variable switching frequency. This lack of control over frequency is the origin of torque and flux ripples. To overcome these problems, this article proposes modified fuzzy direct torque control for an induction motor. In addition, a three-phase pulse width modulation rectifier controlled by the fuzzy direct power control is used. This rectifier draws a sinusoidal current from the grid and operates with a power factor close to unity. The pulse width modulation rectifier feeds the inverter of the direct torque control, ensuring a speed control loop. The proposed direct torque control-direct power control method is investigated based on theoretical analysis, computer simulation, and experimental validation that provide acceptable results.Öğe Introduction to Smart Grid(IEEE, 2016) Colak, IlhamiSmart grid can be defined as self-sufficient systems, which allows integration of any type and any scale generation sources to the grid that reduces the workforce targeting sustainable, reliable, safe and quality electricity to all consumers. Associations of initial studies for the next step in smart grid applications will provide an economical benefit for the authorities in the long term, and will help to establish standards to be compatible with every application. So that all smart grid applications can be coordinated under the control of same authorities. Even though these technological application studies constitute an initial step for the structure of the smart grid, they have not been fully accomplished in many countries. In this study, the introduction to smart grids is given as an overview.Öğe Multi-time series and-time scale modeling for wind speed and wind power forecasting part I: Statistical methods, very short-term and short-term applications(Institute of Electrical and Electronics Engineers Inc., 2015) Colak, Ilhami; Sagiroglu, Seref; Yesilbudak, Mehmet; Kabalci, Ersan; Ibrahim Bulbul, H.This study concentrates on multi-time series and-time scale modeling in wind speed and wind power forecasting. Different statistical models along with different time horizons are analyzed and evaluated broadly and comprehensively. For this reason, the entire study is divided into two main scientific parts. In case of making a general overview of the entire study, moving average (MA), weighted moving average (WMA), autoregressive moving average (ARMA) and autoregressive integrated moving average (ARIMA) methods are employed for multi-time series modeling. Very short-term, short-term, medium-term and long-term scales are utilized for multi-time scale modeling. Specifically, in this part of the entire study, the mentioned statistical models are presented in detail and 10-min and 1-h time series forecasting models are created for the purpose of achieving 10-min and 2-h ahead forecasting, respectively. Many useful outcomes are accomplished for very short-term and short-term wind speed and wind power forecasting. © 2015 IEEE.Öğe Multi-time series and-time scale modeling for wind speed and wind power forecasting part II: Medium-term and long-term applications(Institute of Electrical and Electronics Engineers Inc., 2015) Colak, Ilhami; Sagiroglu, Seref; Yesilbudak, Mehmet; Kabalci, Ersan; Ibrahim Bulbul, H.This paper represents the second part of an entire study which focuses on multi-time series and-time scale modeling in wind speed and wind power forecasting. In the first part of the entire study [1], firstly, moving average (MA), weighted moving average (WMA), autoregressive moving average (ARMA) and autoregressive integrated moving average (ARIMA) models are introduced in-depth. Afterwards, the mentioned models are analyzed for very short-term and short-term forecasting scales, comprehensively. In this second part of the entire study, we address the medium-term and long-term prediction performance of MA, WMA, ARMA and ARIMA models in wind speed and wind power forecasting. Particularly, 3-h and 6-h time series forecasting models are constructed in order to carry out 9-h and 24-h ahead forecasting, respectively. Many valuable assessments are made for the employed statistical models in terms of medium-term and long-terms forecasting scales. Finally, many valuable achievements are discussed considering a detailed comparison chart of the entire study. © 2015 IEEE.Öğe A novel intelligent approach for yaw position forecasting in wind energy systems(Elsevier Sci Ltd, 2015) Yesilbudak, Mehmet; Sagiroglu, Seref; Colak, IlhamiYaw control systems orientate the rotor of a wind turbine into the wind direction, optimize the wind power generated by wind turbines and alleviate the mechanical stresses on a wind turbine. Regarding the advantages of yaw control systems, a k-nearest neighbor classifier (k-NN) has been developed in order to forecast the yaw position parameter at 10-min intervals in this study. Air temperature, atmosphere pressure, wind direction, wind speed, rotor speed and wind power parameters are used in 2, 3, 4, 5 and 6-dimensional input spaces. The forecasting model using Manhattan distance metric for k= 3 uncovered the roost accurate performance for atmosphere pressure, wind direction, wind speed and rotor speed inputs. However, the forecasting model using Euclidean distance metric for k= 1 brought out the most inconsistent results for atmosphere pressure and wind speed inputs. As a result of multi-tupled analyses, many feasible inferences were achieved for yaw position control systems. In addition, the yaw position forecasting model developed was compared with the persistence model and it surpassed the persistence model significantly in terms of the improvement percent. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Novel User Modeling Approaches for Personalized Learning Environments(World Scientific Publ Co Pte Ltd, 2016) Kahraman, H. Tolga; Sagiroglu, Seref; Colak, IlhamiModeling user knowledge and creating user profiles not only for special web-based social media but also for complex and mixed personalized learning environments are important research challenges. The key component for adaptation is the user's knowledge model. This paper introduces fuzzy metric (FM)-based novel and efficient similarity measurement method and adaptive artificial neural network (AANN) and artificial bee colony (ABC)-based knowledge classification approaches for personalized learning environments. For this purpose, FM-based method has been developed to measure distances more efficiently among the users and their knowledge model using the web logs/session data. In addition, a novel knowledge classifier based on ABC and AANN having combined with the generic object model has been developed for user modeling strategies and user modeling server of adaptive educational electric course (AEEC). Finally, the approaches have been tested to compare the classification performance of the user modeling methods developed for user modeling task. The experimental results have shown that proposed methods have improved similarity measurements considerably and decreased the misclassifications in user modeling processes. Thus, powerful user modeling approaches have been presented to the literature. It is expected that the approaches introduced in this article can be a reference to others researches and to develop more adaptive and personalized web applications in future.Öğe Optimum Control Strategy based on an Equivalent Sliding Mode for Solar Systems with Battery Storage(IEEE, 2016) Belkaid, Abdelhakim; Colak, Ilhami; Kayisli, KorhanExtracting the maximum power point (MPP) from the photovoltaic (PV) panel is very difficult due to its non linear I-V characteristic which is impacted by dynamic fluctuations in irradiance and temperature. This paper presents a modified equivalent sliding mode control (MESM), aiming to maximize the PV array output power. This method is applied to buck converter that is employed as interface between the PV generator and the battery to adjust the voltage levels and to track the maximum power from the PV array. To prove its (structure, converter, control algorithm) effectiveness, the proposed tracker is compared with the classical one (ESM) using the trapezoidal irradiance test as recommended by EN 50530. The results indicate that the proposed method can follow the MPP with best performance in static and dynamic states. In average, the performance of the proposed method is found to be slightly greater giving 99.60% efficiency compared to 97.99% in the conventional technique. Performance of the proposed technique has been tested through Matlab/SimulinkTM simulations.Öğe PV Module Parameters Extraction with Maximum Power Point Estimation Based on Flower Pollination Algorithm(IEEE, 2016) Benkercha, Rabah; Moulahoum, Samir; Colak, Ilhami; Taghezouit, BilalModeling of photovoltaic (PV) module remains as an important issue for many applications like monitoring or fault detection. Hence, many models have been proposed in literature, the most popular ones are the single and double diode models. Each model have unknown parameters to be identified. In this paper, a parameters extraction for both single and double diode models by using flower pollination algorithm is proposed. This algorithm is based on flower pollination for optimal reproduction of the plants species and can be considered as an optimization technique. Experimental validation was carried out by comparing the obtained results with real measurements data. In order to give usefulness, the extracted PV module parameters values are incorporated to estimate the maximum power point (MPP) and compared it with the MPP obtained from real data of grid connected photovoltaic system (GCPVS).Öğe Smart grid projects in Europe: Current status, maturity and future scenarios(Elsevier Sci Ltd, 2015) Colak, Ilhami; Fulli, Gianluca; Sagiroglu, Seref; Yesilbudak, Mehmet; Covrig, Catalin-FelixThe attention on the smart grids and smart grid technologies has grown significantly over the last few years. The analysis made in this study is grounded on the smart grid projects database of the Joint Research Centre (European Commission). The European smart grid projects are analyzed among others in terms of: number, countries, duration and collaboration. Additionally, an analysis is done regarding the annual number of starting and concluded/planned to be concluded projects, the total number of participants per year, the distribution of smart grid applications per stage of development, year and EU country and an overview of the investments in the European smart grid projects is provided. Afterwards a forecast is done regarding the number of projects. As a result of graphical and predictive analyses, many essential inferences are achieved related to the current status and the anticipated short-term trends of smart grid projects. (C) 2015 Elsevier Ltd. All rights reserved.Öğe A survey on the contributions of power electronics to smart grid systems(Pergamon-Elsevier Science Ltd, 2015) Colak, Ilhami; Kabalci, Ersan; Fulli, Gianluca; Lazarou, StavrosThe smart grid (SG) as a research area is advancing dealing with a wider range of topics such as power systems, energy generation and telecommunication. The conventional utility grid is used to operate in a passive mode absorbing energy from the substations and delivering it to the customers. This approach is well developed but the needs of the state-of-the-art technology require a bidirectional flow of power and data. Nevertheless, smart grid systems provide more flexible, reliable, sustainable, secure and two-way communication service. Especially, integration of renewable energy sources, electrical vehicles and distributed generations (DG) into network can be achieved in an efficient way in smart grid systems. Moreover, control and monitoring capabilities, automatic configuration of the grid, and active involvement of consumers in energy production extend the importance of smart grids. All these positive aspects of smart grids have been attained by integration of power electronics and telecommunication technologies with the grid. This study deals with contributions of power electronics to SG in the context of generation, conversion, distribution, and control of power. The recent power electronic devices and systems adapted to SG are also introduced in detail with several power control methods. Moreover, the renewable energy sources (RESs), which are an extensively studied topic of power engineering and their integration to smart grid, are also surveyed in terms of DG units, control and management features. Thus, a particular section is dedicated to RES utilization in SG covering almost all aspects of a monotype and hybrid energy plants. Finally, the survey is carried on by reviewing the most recent and comprehensive articles to highlight the importance of power electronics in a logical way in the smart grids for readers. (C) 2015 Elsevier Ltd. All rights reserved.Öğe A survey on the critical issues in smart grid technologies(Pergamon-Elsevier Science Ltd, 2016) Colak, Ilhami; Sagiroglu, Seref; Fulli, Gianluca; Yesilbudak, Mehmet; Covrig, Catalin-FelixThe hierarchical and the centrally-controlled grid topology of existing electrical power systems has remained unchanged over the 20th century. On the other hand, there is a rapid increase in the cost of fossil fuels coupled with the inability of utility companies to expand their generation capacity in line with the rising electricity demand, without modernizing the grid. For these reasons, it is needed to modernize the existing power grids and consequently smart power grids have emerged. Unlike the benefits and features ensured by smart grids, this paper provides a detailed survey of the critical challenges in smart grids in terms of information and communication technologies, sensing, measurement, control and automation technologies, power electronics and energy storage technologies. It is expected that this paper will lead to the better understanding of potential constraints in smart grid technologies. (c) 2015 Elsevier Ltd. All rights reserved.Öğe Welcome to ISGWCP 2016(Institute of Electrical and Electronics Engineers Inc., 2016) Gayretli, Abdulkadir; Aykac, Burhan; Colak, Ilhami[No abstract available]
