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https://hdl.handle.net/20.500.12684/7026

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Enhancement of demagnetization control for low-voltage ride-through capability in DFIG-based wind farm
(Springer, 2018) Döşoğlu, Mehmet Kenan; Güvenç, Uğur; Sönmez, Yusuf; Yılmaz, Cemal
Low voltage ride through (LVRT) is one of the most popular methods to protect doubly fed induction generator (DFIG) against balanced and unbalanced voltage dips. In this study, a novel LVRT capability strategy is enhanced using forcing demagnetization controller (FDC) in DFIG-based wind farm. Moreover, not only stator circuit but also rotor circuit were developed by electromotor force (EMF) for LVRT in DFIG-based wind farm. The transient stability performances of the DFIG with and without the FDC and EMF were compared for three- and two-phase faults. In addition to variations such as 34.5 kV bus voltage and terminal voltage of DFIG, speed of DFIG, electrical torque of DFIG and d-q axis rotor-stator current variations of DFIG were also evaluated. It was seen that the system became stable within a short time using the FDC and EMF.
Enhancement of a reduced order doubly fed induction generator model for wind farm transient stability analyses
(Tubitak Scientific & Technical Research Council Turkey, 2016) Döşoğlu, Mehmet Kenan; Arsoy, Ayşen Basa
Dynamic modeling of a doubly fed induction generator (DFIG) implemented for wind power systems is very important for transient stability. The rotor dynamic model (RDM) as well as the reduced order model (ROM) of a DFIG has been developed for transient analysis purpose. The performances of reduced order DFIG models with/without RDM have been compared. Modeling and analyses have been carried out in MATLAB/SIMULINK. Comparison of system behaviors against 3 phase fault is made between without RDM and with RDM. Several parameters such as output voltage, active power, speed, electrical torque variations, and d-q axis stator and rotor current variations of the DFIG along with a 34.5 kV bus voltage have been examined. In addition, the responses of DFIG output voltage and electrical torque have been compared for the cases of full order and reduced order DFIG models with rotor dynamics. It has been seen that the system becomes stable in a short time when the rotor dynamic is included in a reduced order DFIG model.
Enhancement of SDRU and RCC for low voltage ride through capability in DFIG based wind farm
(Springer, 2017) Döşoğlu, Mehmet Kenan
Grid-integrated wind turbine may experience low voltages during transient events in grid. An increase observed in inrush current leads to low voltage. To control the increased current, an enhancement in a low voltage ride-through (LVRT) capability is required. This study examines the impact of an LVRT scheme on grid-integrated doubly fed induction generator (DFIG)-based wind turbines which are represented with new stator-damping resistor unit (SDRU) and rotor current control (RCC). Besides, both stator and rotor circuits of DFIG were enhanced with electro-motor force (emk). Designed as hybrid with SDRU and RCC, DFIG was examined to analyses symmetrical and asymmetrical faults in the grid. Electro-motor-force dynamic modeling of both stator and rotor was developed. The responses of wind turbine against low voltage are investigated in terms of bus voltages, angular speed, electrical torque, stator and rotor current, and d-q axes current. The results of the study show that the system became stable in a short time when the SDRU and RCC were incorporated with the stator and rotor electro-motor-force models.
Hybrid low voltage ride through enhancement for transient stability capability in wind farms
(Elsevier Sci Ltd, 2016) Döşoğlu, Mehmet Kenan
Protection of a doubly fed induction generator (DFIG) implemented for both wind farm and power systems is very important for transient stability. Crowbar circuits have been used for protection of DFIGs; however, a crowbar circuit is insufficient in terms of transient stability. Therefore, in this study, the passive Low voltage Ride Through (LVRT) capability method as well as the active LVRT capability method were developed for the purpose of transient analysis of the DFIG. The performances of DFIG models with and without active LVRT were compared. Modelling was carried out in a MATLAB/SIMULINK environment. Comparisons were made between behaviours of 3-phase fault and 2-phase fault systems and between rotor dynamic systems and those without a rotor dynamic. Parameters included DFIG output voltage, active power, speed, electrical torque variations and d-q axis stator current variations. In addition, a 34.5 kV bus voltage was examined. It was found that the system became stable in a short time when the active LVRT was incorporated into the reduced order DFIG model. (C) 2015 Elsevier Ltd. All rights reserved.
Gravitational search algorithm for determining controller parameters in an automatic voltage regulator system
(Tubitak Scientific & Technical Research Council Turkey, 2016) Duman, Serhat; Yörükeren, Nuran; Altaş, İsmail H.
This paper presents optimal tuning of the controller parameters of a proportional-integral-derivate (PID) controller for an automatic voltage regulator (AVR) system using a heuristic gravitational search algorithm (GSA) based on mass interactions and Newton's law of gravity. The determination of optimal controller parameters is considered an optimization problem in which different performance indexes and a performance criterion in the time domain have been used as objective functions to test the performance and effectiveness of the GSA. In the determining process of the parameters, the designed PID controller with the proposed approach is simulated under different conditions and the performance of the controller is compared with those reported in the literature. From the numerical simulation results it is clear that the GSA approach is successfully applied to reveal the performance and the feasibility of the proposed controller in the AVR system.
Fuzzy diffusion filter with extended neighborhood
(Pergamon-Elsevier Science Ltd, 2013) Elmas, Çetin; Demirci, Recep; Güvenç, Uğur
Anisotropic diffusion filters, which are motivated from heat diffusion between mediums, have become a widely used technique in the field of image processing. In the initial proposals of anisotropic diffusion filters, 4-neighborhood values with diffusivity functions are computed independently for each spatial location because of numerical approximation. However, anisotropic diffusion filters could not be used in real-time image and video processing applications because they need diffusivity parameters, which must be specified by users in every sampling period. In this study, a fuzzy adaptive diffusion filter using extended neighborhood without diffusivity functions has been developed. The fuzzy adaptive diffusion filter does not require any parameter chosen by user and therefore they could be employed in real-time applications. In the fuzzy adaptive diffusion filter, a similarity transformation by means of relation matrix and fuzzy logic is carried out. Accordingly, the similarity image, output of transformation, is directly used as a heat diffusion coefficient in the diffusion filter. Results show that the fuzzy adaptive diffusion filter is very efficient for removing noise in image while preserving edges. (C) 2012 Elsevier Ltd. All rights reserved.
Fuzzy Logic Based Approach to Site Selection Problem of Vocational Secondary School Students
(Hacettepe Univ, 2017) Güler, Osman; Yücedağ, İbrahim
In this study a fuzzy logic-based decision support system has been developed in order to help field selection problems of vocational high school students. As input parameters, the results of academic self-concept scale that applied to students and the notes that students have taken from the courses were used. In the system output the areas in which students are expected to be successful is guessed. In the study, academic self concept scales' results and fuzzy logic-based Academic self-concept scales' results were compared. It is seen that according to fuzzy logic-based Academic self concept scales students will be successful in some departments that they will be fail according to Academic self concept scales or according to fuzzy logic-based Academic self concept scales students will be fail in some departments that they will be successful according to Academic self concept scales.
Developing and modeling of voice control system for prosthetic robot arm in medical systems
(Elsevier Science Bv, 2018) Gündoğdu, Köksal; Bayrakdar, Sümeyye; Yücedağ, İbrahim
In parallel with the development of technology, various control methods are also developed. Voice control system is one of these control methods. In this study, an effective modelling upon mathematical models used in the literature is performed, and a voice control system is developed in order to control prosthetic robot arms. The developed control system has been applied on four-jointed RRRR robot arm. Implementation tests were performed on the designed system. As a result of the tests; it has been observed that the technique utilized in our system achieves about 11% more efficient voice recognition than currently used techniques in the literature. With the improved mathematical modelling, it has been shown that voice commands could be effectively used for controlling the prosthetic robot arm. (C) 2017 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University.
Walsh Function Based PWM AC Chopper Voltage Controller
(Praise Worthy Prize Srl, 2012) Kale, M.
This paper presents a selective harmonic elimination PWM AC chopper technique based on the Walsh function. Selective harmonic elimination technique calculated by the Fourier series involves solution of nonlinear transcendental equations. The switching angles of PWM AC chopper are calculated by solving linear algebraic equations obtained by the Walsh function approach in order to accurately cancel selected harmonic components of load voltage. Employing the proposed method, the selected harmonics of output voltage are eliminated and hence harmonic contents together with magnitude of output voltage can be adjusted in a wide range. In the experimental implementation, a capacitor-run single phase induction motor is driven by the proposed the Walsh function based PWM AC chopper. Numerical simulations and experimental results demonstrate the performance and feasibility of the proposed method. Copyright (C) 2012 Praise Worthy Prize S.r.l. - All rights reserved.
Transient modeling and analysis of a DFIG based wind farm with supercapacitor energy storage
(Elsevier Sci Ltd, 2016) Döşoğlu, Mehmet Kenan; Arsoy, Aysen Basa
Energy storage system (ESS) coupled to a wind generator has been recommended in improving the stability of the power system to which the wind farm is connected. ESS is particularly preferred in enhancing low voltage ride through (LVRT) capability owing to its fast charging and efficiency for high power applications. In the present study, a supercapacitor type ESS is used in transient state analysis of a grid connected wind turbine. The ESS consisting of a supercapacitor and a voltage buck-boost converter circuit is mathematically modeled in the grid side converter circuit of a doubly fed induction generator (DFIG) used as a wind generator. Moreover, reduced order model (ROM) for the DFIG is used in simulating stator dynamics. All modeling study has been carried out in MATLAB/SIMULINK environment. Three phase faults and having static loads for a short period of time are considered as transient cases. The effectiveness of the ESS on LVRT are shown by observing the responses of several system parameters. The study results show that utilizing a nonlinear supercapacitor type ESS in a ROM based DFIG removes oscillations in a short time during transient states, therefore enhances LVRT. (C) 2015 Elsevier Ltd. All rights reserved.
THE ANALYSIS OF DIFFERENT TECHNIQUES FOR SPEED CONTROL OF PERMANENT MAGNET SYNCHRONOUS MOTOR
(Univ Osijek, Tech Fac, 2015) Dursun, Mustafa; Boz, Ali Fuat
This paper presents the use of proportional integral (PI), proportional integral derivative (PID) and fuzzy logic (FL) speed controller techniques in the permanent magnet synchronous motor (PMSM) drive. PI and PID controllers require precise linear mathematical model of the system. On the other hand, FL needs linguistic description of the system. The dynamic response of PMSM with the controllers was studied under different load disturbances. The effectiveness of the fuzzy logic controller was compared with the conventional PI and PID controllers. The FL controller responded better than conventional techniques under transient load conditions and also achieved faster settling response.
Symbiotic organisms search algorithm for optimal power flow problem based on valve-point effect and prohibited zones
(Springer London Ltd, 2017) Duman, Serhat
In this study, symbiotic organisms search (SOS) stochastic method is proposed to solve the optimal power flow (OPF) problem with valve-point effect and prohibited zones, which is one of the most important problems of the modern power system. The SOS approach is defined as the symbiotic relationships observed between two organisms in the ecosystem, which do not need the control parameters unlike other meta-heuristic algorithms in the literature. The effectiveness of the proposed SOS method is tested on modified IEEE 30-bus test system. The OPF problem is considered with four different test cases, such as (1) without valve-point effect and prohibited zones, (2) with valve-point effect, (3) with prohibited zones and (4) with valve-point effect and prohibited zones. The obtained results from the SOS algorithm are compared with the other optimization techniques in the literature. The obtained comparison results indicate that proposed approach is effective to reach optimal solution for the OPF problem.
Symbiotic organisms search algorithm for dynamic economic dispatch with valve-point effects
(Taylor & Francis Ltd, 2017) Sönmez, Yusuf; Kahraman, H. Tolga; Döşoğlu, M. Kenan; Güvenç, Uğur; Duman, Serhat
In this study, symbiotic organisms search (SOS) algorithm is proposed to solve the dynamic economic dispatch with valve-point effects problem, which is one of the most important problems of the modern power system. Some practical constraints like valve-point effects, ramp rate limits and prohibited operating zones have been considered as solutions. Proposed algorithm was tested on five different test cases in 5 units, 10 units and 13 units systems. The obtained results have been compared with other well-known metaheuristic methods reported before. Results show that proposed algorithm has a good convergence and produces better results than other methods.
Solution of the Optimal Power Flow Problem Considering FACTS Devices by Using Lightning Search Algorithm
(Springer International Publishing Ag, 2019) Duman, Serhat
In this study, the optimal power flow (OPF) problem including flexible AC transmission systems (FACTS) devices, ever increasing in the planning and operating of the modern power systems has been addressed. The thyristor-controlled series capacitor and the thyristor-controlled phase shifter are used as FACTS devices. The solution to this problem is proposed by using a new heuristic algorithm known as the lightning search algorithm (LSA) based on the phenomenon of lighting. The LSA method is generalized from the mechanism of step leader propagation. The performance, success and robustness in the solution of this problem of the LSA are evaluated and tested on IEEE test systems, which are the modified IEEE 30-bus and IEEE 57-bus test systems. The multi-objective functions are used in the solution analysis processes of this problem. These objective functions are defined as the minimization of the fuel cost, minimization of the emission and minimization of the active power loss of the test system. The numerical results of the LSA are compared to different methods presented in the recent literature, which are ant lion optimizer, grey wolf optimizer, dragonfly algorithm, moth-flame optimization. The outcomes obtained from simulation study indicate the potential of the LSA method in solving the OPF problem including FACTS devices for operating and planning of the modern power systems.
Short Term Load Forecasting for Turkey Energy Distribution System with Artificial Neural Networks
(Univ Osijek, Tech Fac, 2019) Tosun, Salih; Öztürk, Ali; Taşpınar, Fatih
The constant increase in consumption of electricity has become one of the biggest problems today. The evaluation of energy resources has also made it worthwhile to consume it. In this respect, the transmission of electric energy and the operation of power systems have become important issues. As a result, reliable, high quality and affordable energy supply has become the most important task of operators. Realizing these elements can certainly be accomplished with good planning. One of the most important elements of this planning is undoubtedly consumption estimates. Therefore, knowing when consumers will consume energy is of great importance for operators as well as energy producers. Consumption estimates or, in other words, load estimates are also important in terms of the price balance that will occur in the market. In this study, the short-term load estimation of Duzce, Turkey is performed with Artificial Neural Networks (ANN). In the study, the April values were taken as reference and the estimates were obtained according to the input results of this month. As a result of this study, it is seen that the load consumption with nonlinear data can be successfully forecasted by ANN.
Sensorless control application of PMSM with a novel adaptation mechanism
(Springer, 2018) Dursun, Mustafa; Boz, Ali Fuat; Kale, Murat; Karabacak, Murat
This paper proposes a novel adaptation design to replace the classical proportional-integral controller used in model reference adaptive system (MRAS) speed estimation. The proposed adaptation scheme is an association of two fuzzy units. The rules of each module were obtained by user experience and numerical data. In the traditional fuzzy logic controllers, the computational complication enhances with the attributes of the system variable quantities; the number of rules increases incrementally while the number of control variables increases. This negatively affects the response time of the system. This novel design was deduced to reduce the number of rules for a linear function of system variables. By this way, the response of the system became faster. Detailed simulation and experimental results were obtained for comparison of this novel method with traditional MRAS techniques. The results showed that the proposed method was faster in speed tracking and exhibited higher prediction accuracy and less oscillation than the traditional method. Thus, the proposed MRAS method was clearly seen to be applicable and reliable.
Performance analysis of biogeography-based optimization for automatic voltage regulator system
(Tubitak Scientific & Technical Research Council Turkey, 2016) Güvenç, Uğur; Yiğit, Tuncay; Işık, Ali Hakan; Akkaya, İbrahim
A self-tuning method to determine the appropriate parameters of a proportional-integral-derivative controller for an automatic voltage regulator (AVR) system using a biogeography-based optimization (BBO) algorithm is proposed in this study. The BBO algorithm was developed based on the theory of biogeography, which describes migration and its results. We propose that the BBO algorithm has a high-quality solution and stable convergence characteristics, and thus it improves the transient response of the controlled system. The performance of the BBO algorithm depends on the transient response, root locus, and Bode analysis. Robustness analysis is done in the AVR system, which is tuned by an artificial bee colony (ABC) algorithm in order to identify its response to changes in the system parameters. We compare the BBO algorithm with the ABC algorithm, particle swarm optimization algorithm, and differential evolution algorithm. The results of this comparison show that the BBO algorithm has a better tuning capability than the other optimization algorithms.
Nonlinear dynamic modeling for fault ride-through capability of DFIG-based wind farm
(Springer, 2017) Döşoğlu, Mehmet Kenan
Fault ride-through (FRT) is a control model enhanced to protect doubly fed induction generator (DFIG) during voltage dip occurring in grid. In this study, stator and rotor circuit dynamic modeling enhanced in terms of simulation performance and fast system responses during instability in DFIG-based wind farm, besides, a FRT capability strategy were enhanced for nonlinear supercapacitor modeling in DFIG-based wind farm. The transient stability analyses of the DFIG with and without supercapacitor as well as positive-negative-sequence dynamic modeling (PNSDM) were compared for three phases, two phases, two-phase-ground and a-phase-ground faults. Furthermore, variations such as DFIG output voltage, DFIG angular speed, DFIG electrical torque and DFIG d-q axis stator current variations were also evaluated. It was found that the DFIG-based wind farm became stable within a short time using the PNSDM and supercapacitor.
NEW MODEL ADAPTIVE SYSTEM DESIGN FOR SENSORLESS SPEED CONTROL OF PMSM
(Yildiz Technical Univ, 2017) Dursun, Mustafa
In this study, simulation studies of permanent magnet synchronous motor (PMSM) based on model reference adaptive control method were performed using Matlab / Simulink package program. Instead of the PI controller traditionally used in the Model Reference Adaptive System (MRAS), system performance is examined using fuzzy logic and hierarchical fuzzy logic controllers (HFC). It is clearly seen in the simulation studies that the hierarchical controller is superior to the fuzzy logic controller by giving better dynamic response and less steady state error.
Modeling and simulation of static loads for wind power applications
(Springer, 2014) Döşoğlu, Mehmet Kenan; Arsoy, Aysen Basa
This study aims to model and simulate static nonlinear loads with wind power generation to evaluate the impact of load models on wind power systems. Nonlinear loads are modeled as exponential load model, ZIP load model and combination of exponential/ZIP with an induction motor. The wind power generator is represented with a reduced-order doubly fed induction generator (DFIG) model. Developed models have been implemented in a grid-integrated wind power plant and simulated in MATLAB/SIMULINK. The effects of nonlinear loads into wind power plant are investigated in terms of bus voltages, angular speed, electrical torque, and d-q stator axes currents. Additional analyses are conducted to compare the behaviors of full- and reduced-order DFIG models under a selected loading condition. The results of this study indicate that the response of a system with DFIG is dependent of the load modeling and reduced-order DFIG model shows more stable trend than full-order DFIG model.

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