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Öğe An Active Battery Cell Balancing Topology without Using External Energy Storage Elements(Ieee, 2015) Gokdag, Mustafa; Akbaba, MehmetCell balancing circuits are important to extent lifecycle of batteries and to extract maximum power from the batteries. A lot of power electronics topology has been tried for cell balancing in the battery packages. Active cell balancing topologies transfer energy from the cells showing higher performance to the cells showing lower performance to balance voltages across the cells of the battery using energy storage elements like combination of inductor-capacitor or transformercapacitor or switched capacitor or switched inductor. In this study an active balancing topology without using any energy storage element is proposed. The idea is similar to the switched capacitor topology in which a capacitor or capacitor banks is switched across the cells of battery to balance the voltages. Since a basic battery cell model includes capacitance because of capacitive effect of the cell, this capacitive effect can be utilized in cell balancing. Hence the equalizer capacitors in switched capacitor topology can be eliminated and the cells of battery can be switched with each other. This allows faster energy transfer and hence results in quick equalization. The proposed topology removes the need of extra energy storage elements like capacitors which frequently fails in power electronic circuits, reduces the losses inserted by extra energy storage elements and cost and volume of the circuits and simplifies control algorithm. The proposed balancing circuit can be implemented according to the application requirement. The proposed topology is simulated in MATLAB/Simulink environment and showed better results in terms of balancing speed in comparison to switched capacitor topologies.Öğe Comparison of 2D and 3D magnetic field analysis of single-phase shaded pole induction motors(Elsevier - Division Reed Elsevier India Pvt Ltd, 2016) Dalcali, Adem; Akbaba, MehmetThere has always been doubt on the accuracy of 2D analysis of small electric machines. To investigate the validity of this doubt, in this present work a small uni-coil shaded-pole induction motor is analyzed in 2D and 3D and the results are compared. In order to maintain the paper size as compact, the analysis is limited to the air-gap flux density distribution, variation of the main winding inductance against current and the force acting on the rotor body; which are the important components of the motor performance. It is found that although 3D analysis consumes several times more computing time and storage space, improvement achieved in performance by use of 3D analysis is not very significant. % rms difference between the two cases is obtained as 0.76% for the main winding inductance and 0.59% for the force acting on the rotor body. Also the air-gap flux density distribution obtained from the two types of analysis is found to be very close to each other. Therefore it is concluded that despite more computing time, more storage requirements and more human effort in the case of 3D analysis, the degree of improvement is not proportionally rewarding, and hence, 2D analysis is sufficient for the analysis of small machines. (C) 2015, Karabuk University. Production and hosting by Elsevier B.V.Öğe Comparison of the performance of bridge and bridgeless shaded pole induction motors using FEM(Ios Press, 2017) Dalcali, Adem; Akbaba, MehmetTwo 15W shaded pole motors with bridged and without bridge type stators were modeled using 2D and 3D analysis were performed using finite element analyzes. The magnetic behavior of the motor was determined by obtaining the magnetic flux density over the cross section of the motor and the air gap flux waveforms. Recently, a new modified structure of these motors has started to be seen in the literature, and this structure is called the bridged structure. The flux value transferred to the rotor in bridgeless motors is greater than with the bridged stator type. The harmonic components were obtained by making the Finite Fourier analyses of the waveforms of flux densities. It was determined that the bridged structure had the disadvantage of having stronger harmonics than the bridgeless structure. The magnetic performances of 4 different rotor structures were examined in the rotor part of the bridgeless- type motor. The number of rotor slots were modified between 16 and 32 by selecting Type 1 on these different rotors. The optimum number of rotor slots was determined to be 26. It was stated that determining the optimum number of slots in the design of these motors would provide significant improvement in the performance.Öğe Değişken hava aralıklı gölge kutuplu asenkron motorun faz endüktanslarının tespitine yönelik detaylı bir çalışma(2019) Dalcalı, Adem; Akbaba, Mehmet; Çelik, EmreGölge kutuplu asenkron motorlar (GKAM) yapılarının basit, maliyetlerinin düşük olması ve az bakıma ihtiyaç duymaları nedeniyle endüstriyel uygulamalarda, ev aletlerinde ve havalandırma sistemlerinde yoğun bir şekilde kullanılmaktadırlar. GKAM’da eliptik döner alanın oluşumu motorun analizini oldukça zorlaştırmaktadır. Bu karmaşıklığın sonucu olarak, bu tip motorların teorisi, tasarımı ve analizi konusunda nispeten sınırlı yayın bulunmaktadır. Çoğunlukla bu motorların tasarımları deneme-yanılma yöntemine dayanmaktadır. Bilindiği üzere elektrik makinalarının performansının doğru bir şekilde hesaplanması, hesaplamalarda kullanılan sargı endüktanslarının doğruluğu ile yakından ilişkilidir. Bu nedenle, çalışmada 4 kutuplu GKAM’ın stator sargısı ve gölge kutup sargısı sargı başı endüktansı, stator sargısı öz endüktansı, stator sargısı toplam kaçak endüktansı ve stator-rotor ortak endüktansı analitik denklemler ve gerçek zamanlı deneyler yardımıyla elde edilmiştir. Aynı zamanda manyetik doyumun stator öz endüktansı ve kaçak endüktansına etkisi ile stator-rotor ortak endüktansının rotor pozisyonuyla değişimi incelenmiştir. Çalışmanın sonunda, hesaplanan stator sargısı öz endüktansının doğruluğu deneysel bir yaklaşımla doğrulanmıştır.Öğe Detection of the space harmonics of the shaded pole induction motor(Academic Publication Council, 2017) Dalcali, Adem; Akbaba, MehmetIn many cases, shaded pole induction motors have variable air gaps, and because of this, their air-gap flux density waveforms are too far from a sinusoidal distribution. Utilizing of variable air-gap in shaded pole motors contributes to the starting torque by inducing reluctance torque component. However, variable air-gap introduces additional harmonic components in the airgap flux density waveforms. In this study, detection of the space harmonics of the shaded pole induction motor has been realized. To be able to detect the space harmonics, the rotor of the motor has been produced in a way that aluminum has not been cast, and the short circuit rings of the rotor has have not been inserted. A search-coil whose number of turns is known has been wound to the rotor, rated voltage has been applied to the stator, and the position of the rotor has been varied with a step electrical angle of 3.6o with the help of a step motor. The mutual inductance between the stator and rotor has been determined by reading the voltage induced across the search-coil. The attained mutual inductance waveform has been subjected to Discrete Fourier analysis. From the analyses, it has been observed that especially the 3rd, 5th, and 7th harmonics, especially, are very significant. Other harmonics up to 13th are above 1% of the fundamental component, and the 15th and subsequent harmonics decreases below 0.8% of the fundamental component of the air-gap flux density waveform. Therefore, for a reasonably accurate performance, an analysis of this these machines, at least 3rd, 5th, and 7th harmonics, should be considered.Öğe Determination of the effects of operating conditions on the output power of the inverter and the power quality using an artificial neural network(Elsevier - Division Reed Elsevier India Pvt Ltd, 2019) Yilmaz, Mustafa; Kayabasi, Erhan; Akbaba, MehmetIn this study, the effects of operating conditions of photovoltaic (PV) panels in a power plant installed in Burdur province in Turkey with 8 MW capacity, the output power of the inverter and the power quality in the grid were examined experimentally in January and July. In addition, an artificial neural network (ANN) was utilized to estimate the power at the output of the inverter under different operating conditions and optimal operating conditions were attempted to be determined. In the ANN configuration, the output power generated in PV panels (P-DC), radiation intensity, relative humidity and temperature measurements were used as input data, output power (P-AC) at the junction of the inverter, power factor (PF) and the frequency values were used as output data. In order to ensure the integration of the energy obtained from the solar power plant by using the obtained results, it was tried to estimate the levels of the factors affecting the inverter output power and efficiency in terms of the proper operating conditions and efficiency. The success level of the ANN results was observed to be above 99% with the experimental results. (C) 2019 Karabuk University. Publishing services by Elsevier B.V.Öğe Development of a new microcontroller based MPPT method for photovoltaic generators using Akbaba model with implementation and simulation(Pergamon-Elsevier Science Ltd, 2016) Goksenli, Nurettin; Akbaba, MehmetA novel microcontroller based maximum power point tracker (MPPT) circuit for small scale, stand-alone photovoltaic generators, PVGs, has been built, simulated and tested. The I-V characteristic of PVG is characterized using five solar radiation dependent parameters, two of which are short circuit current and open circuit voltage of PVGs. A DC/DC converter is used as a matching circuit between the load and PVG. Selecting a suitable fixed frequency, the duty cycle (delta) of DC/DC converter has been determined adaptively by microcontroller, by getting feedback from the instantaneous value of the output voltage. As such the system is suitable for dynamic and static loads. Therefore the system needs two measurements, which are solar radiation intensity and feedback from the output voltage across the load, which are fed to microcontroller. The measured solar radiation intensity is converted by microcontroller into percent solar radiation, G, where the highest ever value of the solar radiation intensity in the location is fed to the microcontroller as the base value. The system parameters are PVC dependent and need to be obtained separately for every PVC. A prototype has been built and reasonable correlation is obtained between the measured and simulated results. (C) 2016 Elsevier Ltd. All rights reserved.Öğe Electric Circuit-Based Modeling and Analysis of the Translational, Rotational Mechanical and Electromechanical Systems Dynamics(Ieee-Inst Electrical Electronics Engineers Inc, 2022) Akbaba, Mehmet; Dakkak, Omar; Kim, Byung-Seo; Cora, Adnan; Nor, Shahrudin AwangTo cope with the rapid development in technology, engineers are dealing with complex and heterogenous systems composed of blocks that belong to different engineering fields such as electrical, mechanical, chemical, electromechanical, fluid, thermal, etc. Mechanical and electrical systems more often go hand to hand in many industrial systems. For system analyzing and designing purposes, engineers must model and simulate the systems to investigate problems and aim for the best performance before proceeding to the manufacturing stage. In the presence of complex mechanical system blocks, electrical and electronics engineers are often facing difficulties in modeling the mechanical blocks. Although the similarity between individual mechanical and electrical elements is recognized for a long time, it has not drawn deserved attention for its use at the system level. In this paper, we investigate in great detail how enabling electrical and electronics engineers to easily model and analyze complex mechanical and electromechanical systems through a systematic approach. For this objective, thirteen rules are set, established, and elaborated on how to find the electrical circuit equivalent of a given mechanical or electromechanical system in order to be modeled and analyzed. The proposed approach is tested on both complex translational mechanical and electromechanical systems which includes a rotational mechanical system. Findings demonstrate that models generated by the equivalent of electric circuits are matching the models of existing mechanical and electromechanical systems by 100%. The proposed systematic approach is promising and can be widely implemented in several industrial fields.Öğe Implementation of Differential Power Processing Concept to Switched-Capacitor Topology for PV Sub-module Level Power Balancing(Ieee, 2015) Gokdag, Mustafa; Akbaba, MehmetNon-convex power characteristic curve with decreased peak power and with multiple local maxima occurs because of the partial shading and mismatching conditions among the series connected modules/sub-modules/cells. A number of power electronics topology has been proposed to equalize voltage of each series connected sub-module while providing an extra current path circuitry for mismatch current. The equalization is done by energy transfer between the sub-modules which brings all sub-modules to the same operating voltage and this collective operation produces a convex output power curve with increased peak power. A power electronics solution including minimum number of components and having higher efficiency is essential in this type of application from the perspective of installation costs and overall efficiency. This paper realizes a differential power processing (DPP) version of the recently presented sub-module level power balancing topology which uses nearly half of the converter number in comparison to the related literature. The DPP version of the topology provides improvement in efficiency for matched conditions and for some arbitrary partial shading patterns conditions over the string. PSpice simulation results are provided to show advantage of the approach in comparison to single output version.Öğe A Novel Graphical Approach for the Fast Estimation of Filter Capacitor Value and the Output Performance of Various Uncontrolled Rectifier(World Scientific Publ Co Pte Ltd, 2023) Akbaba, Mehmet; Dakkak, Omar; Atasoy, Ferhat; Cora, AdnanThis paper proposes a novel approach for low-power applications for the fast estimation of filter capacitor value and the output performance parameters such as average, and Root Mean Square (RMS) values for the voltage and current considering single-phase full-wave, three-phase half-wave and three-phase full-wave rectifier circuits. For this aim, the novel equations in this work are derived for the average output voltage and rms ripple voltage separately for each of the above-mentioned three rectifier types. Then % ripple factors for each rectifier type are calculated using newly derived equations and plotted versus the newly introduced Normalized Time Constant (NTC). Besides, considering the peak supply voltage as the base voltage, the Per Unit (p.u.) output average voltage and rms ripple voltage for each of the rectifier circuits are computed and plotted versus NTC. These graphs will be normalized graphs since the output values of these graphs have turned into independent of both supply voltage amplitude and supply frequency. Normalized graphs are set up only once for each type of the rectifier circuit. Then, and for a pre-selected ripple factor value, the corresponding NTC value is obtained by straightforward reading from the graphs set up between the % ripple factor and NTC. Once the NTC value has been acquired, using the formula of NTC leads to finding the capacitor value required for the pre-selected ripple factor with one simple step calculation. Furthermore, the p.u. values of the average output voltage and rms ripple voltage values that correspond to the same NTC value are obtained by reading them from the set-up graphs directly. Finally, the efficiency of the proposed method is demonstrated through design examples for each type of rectifier circuit. The three design examples highlight how the output performance values can be obtained easily, accurately and swiftly. Furthermore, the viability of the graphical approach is verified by the experimental results which demonstrate the suitability of the derived equations in the proposed method.Öğe A novel PV sub-module-level power-balancing topology for maximum power point tracking under partial shading and mismatch conditions(Zhejiang Univ, 2016) Gokdag, Mustafa; Akbaba, MehmetPartial shading and mismatch conditions among the series-connected modules/sub-modules suffer from a nonconvex power curve with multiple local maxima and decreased peak power for the whole string. Energy transfer between the sub-modules brings them to the same operating voltage, and this collective operation produces a convex power curve, which results in increased peak power for the string. The proposed topology benefits from the switched-capacitor (SC) converter concept and is an application for sub-module-level power balancing with some novelties, including stopping the switching in absence of shading, string-level extension, and a reduced number of power electronics components as compared to those in the literature. Reduction in the number of power electronics components is realized by the fact that two sub-modules share one SC converter. This leads to reduced power electronics losses as well as less cost and volume of the converter circuit. Insertion loss analysis of the topology is presented. The proposed topology is simulated in the PSpice environment, and a prototype is built for experimental verification. Both simulation and experimental results confirm the loss analysis. This proves that with the proposed topology it is possible to extract almost all the power available on the partially shaded string and transfer it to the load side.Öğe A novel simple method for elimination of DOL starting transient torque pulsations of three-phase induction motors(Elsevier - Division Reed Elsevier India Pvt Ltd, 2021) Akbaba, MehmetThis paper presents a novel method for elimination of transient torque pulsations of three phase induction motors which arises on direct-on-line (DOL) starting. When started DOL, during run-up period, induction motors produce large transient torque pulsations well in excess of full-load torque. These torque pulsations can be detrimental as it may cause shock-loading on the driven equipment and damage to the mechanical system components such as shaft, gear and couplings. Also, high inrush current is drawn by the motor and this, due to extra temperature rise, may cause winding insulation failure and extra stress on power utilities. With this method faster starting is achieved, which result in faster decaying of inrush currents, and hence reduced stress on both the winding insulation and supply utilities. The method is composed of inserting an optimized and series connected capacitor-resistor pair between the motor and the supply in order to eliminate the low frequency transient components available in the stator and rotor currents, which are the root cause of transient torque pulsations. The proposed method is simulated with full details on two different motors and the results obtained are very satisfactory and promising. (C) 2020 Karabuk University. Publishing services by Elsevier B.V.Öğe A Novel Switched-Capacitor Topology for Sub-module Level Maximum Power Point Tracking under Partial Shading and Mismatch Conditions(Ieee, 2015) Gokdag, Mustafa; Akbaba, MehmetPartial shading and mismatching conditions among the series connected modules/sub-modules/cells suffers from nonconvex P-V or P-I characteristic curves with multiple local maxima and decreased peak power for whole string/module including by-pass diodes. This limits the power extraction from whole string/module. Energy transfer or 'charge redistribution' between the sub-modules brings all sub-modules to the same operating point and this collective operation produces a convex P-V or P-I curves which have increased peak power for series connected sub-modules/cells. Then a conventional maximum power point tracking algorithm can be operated to find this maximum. A number of power electronics topologies are proposed to remove multiple local maximum points and to obtain convex P-V or P-I curves with increased peak power while ensuring that a net power gain is positive. The proposed topology benefits from switched-capacitor (SC) converters concept in a different manner and actually is an application of [1]-[3] at submodule level with some novelties; stopping the switching, string level extension. Two sub-modules share one switched capacitor converter and this allows less power electronics component usage which is nearly half of the converter number used in the literature. This advantage leads to reduced power electronics losses, cost and volume of the converter circuits. The insertion loss of the topology under uniform irradiation is calculated as 0.51% for certain values of capacitance and switching frequency. The proposed topology is simulated in PSpice environment. The simulation results confirm the loss analysis given in section II and prove that it is able to extract all the power produced by the partially shaded string and transfer to the load side.Öğe Performance Optimisation of Single-Phase Variable Reluctance Shaded-Pole Motor br(Univ North, 2022) Dalcali, Adem; Akbaba, MehmetShaded pole induction motors' theoretical analysis is quite difficult because of the presence of strong harmonic components and the elliptical rotating field. The change of air gap reluctance is affecting the air gap flux distribution and thus the performance of the motor. In the study, the effect of the change in the SPIM's stator, rotor and squirrel cage on the performance of the motor is analysed by the Finite Element Method. The flux distributions and torque values of the closed-interpoles type and the stator with different interpoles clearances are obtained. The effects of single and double cage structures in the rotor part and the effects of copper and aluminium cage materials in the squirrel cage were analysed. Accor ding to the analyses, it was determined that the single cage motor with aluminium cage material exhibited the best torque performance with a torque value of 1 32.78 mNmÖğe A Simple-Novel Indirect Algorithm for Tracking Maximum Power Under Rapid or Slow Irradiation and Temperature Changes(Ieee, 2014) Gokdag, Mustafa; Akbaba, MehmetA novel indirect method for maximum power point tracking is proposed in this study. The proposed method, utilizing the linear relationship between the solar irradiation and the maximum power point current, directly provides the maximum power point current and hence the maximum power points trajectory. Therefore it does not require utilization of any search algorithm. Also it has been investigated that the maximum power point current is almost independent of the solar module temperature. Due to this interesting behavior, the proposed method has also superior response for the solar modules working under large temperature ranges. Therefore it has significant advantage over the conventional indirect methods using short circuit current or open circuit voltage. The proposed method is implemented on a boost type converter in MATLAB simulation environment and showed better results in terms of stability and power harvested from the solar module. The method is suitable for the solar systems such as used with micro-inverters.Öğe A study on performance increasing in SSVEP based BCI application(Elsevier - Division Reed Elsevier India Pvt Ltd, 2018) Erkan, Erdem; Akbaba, MehmetPeople which are afflicted with neurological conditions or neurodegenerative diseases can't control own muscles by neural pathways. Brain computer interface (BCI) systems offer these people another alternative path from their own neural pathways. This alternative pathway is the direct use of brain signals by a computer without using any vocal muscle. The steady state visual evoked potential (SSVEP) approach currently provides the high performance and reliable communication for the implementation of a non-invasive BCI. In SSVEP based BCI systems, Electroencephalography (EEG) signal detection time (signal window length) and accuracy are the most important performance parameters. Performance is usually measured by Information Transfer Rate (ITR). In the presented paper a SSVEP based BCI robot control application is introduced and system performance is analyzed for different signal window lengths. At first, the number of eye blinks of the subjects is determined by fast eye artifact detection method (FEAD) which based on visual eye blink detection. These eye blink counts are used for system activation. System usability is improved by this control. Two consecutive eye blinks which detecting by FEAD method are used for system activation. System deactivation is also provided by the same command. Synchronous and asynchronous experiments are performed on four healthy subjects for performance analyses. EEG data is analyzed in details by asynchronous experiments. During the synchronous experiments, subjects are tried to complete a predefined route which has twelve steps by navigating the robot (Lego Mindstorms EV3). The minimum energy combination (MEC) and canonical correlation analysis (CCA) methods are applied to EEG segments that are different in length in order to detect SSVEPs in both type experiments. ITR values are calculated for different signal window lengths. The results show that the detection accuracy of the MEC method is similar to that of the CCA method, although it is higher than that of the CCA method in situations where the SSVEP has low strength. In synchronous experiments, using MEC method a system peak ITR of 133.33 bit/min is reached for one subject with a 0.9 s signal window length. This ITR value is higher than previously published studies in the literature for SSVEP based BCI systems. (C) 2018 Karabuk University. Publishing services by Elsevier B.V.Öğe Switched-capacitor converter for PV modules under partial shading and mismatch conditions(Pergamon-Elsevier Science Ltd, 2018) Gokdag, Mustafa; Akbaba, Mehmet; Gulbudak, OzanPartial shading and mismatch among the Photovoltaic (PV) modules is an important issue, which decreases the harvested power from the PV modules, and causes an efficiency problem for renewable energy systems. Several power electronics topologies that allow charge redistribution between the PV modules, have been proposed to balance PV modules which are connected in series. Differential Power Processing (DPP) is a technique which improves the overall efficiency of the power balance system by processing only a fraction of the module power. In this study, the power loss analysis of the switched-capacitor (SC) converter, which is configured in ladder architecture with the PV sub-modules for power balancing purpose, is derived and verified by simulation and experimental works. The proposed loss model predicts the percentage of power loss of the SC converter working under arbitrary partial shading conditions. Switched-Capacitor converter prototype was built and tested using a 140 W photovoltaic module. It is found that for 0-25% overall partial shading the overall efficiency remains above 98%. The experimentally obtained loss is in reasonable agreement with its theoretical counterpart.
