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Öğe An active battery cell balancing topology without using external energy storage elements(Institute of Electrical and Electronics Engineers Inc., 2015) Gokdag, M.; Akbaba, M.Cell balancing circuits are important to extent life-cycle 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 transformer-capacitor 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. © 2015 IEEE.Öğe Detection of the space harmonics of the shaded pole induction motor(University of Kuwait, 2017) Dalcal, A.; Akbaba, M.In 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. © 2017 University of Kuwait. All rights reserved.Öğe Implementation of differential power processing concept to switched-capacitor topology for PV sub-module level power balancing(Institute of Electrical and Electronics Engineers Inc., 2016) Gokdag, M.; Akbaba, M.Non-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. © 2015 Chamber of Electrical Engineers of Turkey.Öğe Modeling and simulation of dynamic mechanical systems using electric circuit analogy(Murat Yakar, 2021) Akbaba, M.Modeling and simulation are prerequisite to analysis and design of engineering systems. Modern engineering systems often are multy disciplinary, i.e., may include blocks from different majors of engineering, such as electrical, mechanical, fluid, etc. Availability of a unified approach for system modeling will make it easy for engineers or researcher from a certain discipline to model the systems from other disciplines. For example, with availability of a unified modeling methodology an electrical engineer will be able to model a system composed of electrical, mechanical and fluid systems. Modeling of complex mechanical systems is not always easy for engineers from other disciplines. On the other hand, it is much easier to establish mathematical model of electric circuits. Furthermore, simulation software is much richer for electric circuits. Therefore, in this paper a methodology is proposed for unifying the modeling of electrical and complex mechanical systems by obtaining electric circuit model of complex mechanic systems. In developing the proposed methodology, analogy between the electrical and mechanical elements have been used as tools. Proposed methodology has been applied to modeling and simulation of a relatively complex mechanical system and benefits accrued from this approach has been discussed. It is further proposed that the approach presented in this paper can be easily extended to modeling of dynamic systems from other engineering disciplines. © Author(s) 2021.Öğe A novel switched-capacitor topology for submodule level maximum power point tracking under partial shading and mismatch conditions(Institute of Electrical and Electronics Engineers Inc., 2015) Gokdag, M.; Akbaba, M.Partial shading and mismatching conditions among the series connected modules/sub-modules/cells suffers from non-convex 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. © 2015 IEEE.Öğe Optimum pole arc offset in permanent magnet synchronous generators for obtaining lowest voltage harmonics(Elsevier Science Bv, 2017) Dalcali, A.; Akbaba, M.In this study, the effect of parametric variation of pole arc offset distance on the performance of a Permanent-Magnet Synchronous Generator (PMSG) used in wind energy applications has been investigated. Fourier analyses of the voltage wave-shapes that are obtained by the parametric variation of the pole arc offset value have been made. The THD is determined for each voltage wave-shape. As a result of optimization study, the efficiency and output power have been kept approximately constant. The THD of the output voltage has decreased. (c) 2017 Sharif University of Technology. All rights reserved.Öğe A simple-novel indirect algorithm for tracking maximum power under rapid or slow irradiation and temperature changes(Institute of Electrical and Electronics Engineers Inc., 2014) Gokdag, M.; Akbaba, M.A 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. © 2014 IEEE.
