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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 Comparison of Boost-Type ?UK'S PWM-Resonant Converter with Conventional Boost Converter(Institute of Electrical and Electronics Engineers Inc., 2018) Gokdag, M.In this study, boost-type ?uk's PWM-resonant converter is compared with the conventional boost converter in terms of required inductor size, efficiency, and dynamic response. The inductor sizes required by both topologies are selected based upon the core geometrical constant design method. It is found out that the PWM -resonant converter offers a significant reduction in the required inductor size. The efficiency measurements are made in simulation by modeling the lossy elements and the simulation results show that the conventional boost converter has a better efficiency characteristic. The dynamic responses of both converters are also compared under closed-loop control and the PWM-resonant converter shows a faster transient regime with lower overshoots. © 2018 IEEE.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 A method to obtain daily total solar insolation (kWh/m2) from daily total output current (Ah) of a PV array(2012) Gokdag, M.; Guneser, M.T.To determine solar energy potential in a certain location and to realize studies of economics and sizing of photovoltaic system applications to be established in this certain location, solar radiation measurement corresponding to this site is critically important. Solar energy atlas of Turkey is extracted using ESRI Solar Radiation Model whose parameters are calibrated with measurements, which cover period of 22 years between 1985 and 2006, by the study made by EIE in 2008. Applicators of solar energy technologies use solar radiation data in studies such as suitability of the site, economics and sizing of the application. For large-scale applications of solar energy conversion technologies, most experts agree that solar radiation data should be accurate to within 5% to assess the resource, estimate the output of a solar system, and determine whether the system can reliably and economically meet daytime demand and energy requirements. It is stated that the atlas extracted by EİE may include 10% error. Additionally data for some cities at the atlas completely depend on the model estimation. So these data include error more than 10%. For these cities with error more than 10%, the performance and economic goals may not be met in the applications. In this study, a method is presented to evaluate the daily total solar insolation (kWh/m2) from the knowledge of daily total PV array output current (Ah) given by the data logger device of photovoltaic system composed from four strings each having two modules occupied in Karabuk University Renewable Energy Engineering Research and Application Center. Universities with similar small systems can collect solar energy data corresponding to their sites using presented method in this study. © Sila Science.Öğe Model Predictive Control for Battery Charger Applications with Active Damping(Institute of Electrical and Electronics Engineers Inc., 2019) Gokdag, M.; Gulbudak, O.This paper presents a model predictive control approach for a current source rectifier that can be used as battery charger fed from three-phase ac grid. The proposed MPC technique allows to charge the battery with a constant current or voltage as what is required for cyclic charge process of batteries. The proposed technique ensures unity input power factor operation for grid side. Instantaneous active and reactive power control combined with active damping technique is achieved to obtain safe charging process. The method does not require any input current sector information, and there is no need for sinusoidal input current reference synchronized with grid voltage. The proposed control method requires only active power demand to control whole system. A simulation study is carried out to observe the proposed method in terms of steady-state and dynamic responses and supply current quality. © 2019 IEEE.Öğe Model Predictive Control of Two Separate Induction Machines using Dual-Output Indirect Matrix Converter(Institute of Electrical and Electronics Engineers Inc., 2019) Gulbudak, O.; Gokdag, M.Predictive torque and flux control methods for two separate induction machines fed by dual-output indirect matrix converter is presented in this paper. Mathematical models of induction machine and power stage are used to predict future behavior of control objectives and best switching combination is selected by evaluating multi-objective cost function. Basically, torque and flux errors are considered in a user defined cost function and proposed control approach aims to minimize these errors. The method is validated through simulation results where it is shown that dual-output indirect matrix converter combined with predictive control approach can control two induction machines independently. © 2019 IEEE.Öğe Model Predictive Sliding Surface Control of Induction Motor fed by Direct Matrix Converter(Institute of Electrical and Electronics Engineers Inc., 2022) Gulbudak, O.; Gokdag, M.; Komurcugil, H.This paper presents a novel induction motor control strategy for a direct matrix converter. The proposed method consists of two cascaded-control blocks: the stator current control block and the supply current control block. The stator current control block uses the sliding mode control stability term to formulate the objective function. The composed objective function includes the stability expression to regulate the motor speed, torque, and stator current. The second control block contains the predictive active damping method to improve supply current quality. In grid-connected converters, the supply current may suffer from distorted harmonics. To overcome this problem, a damping current is injected into the reference signal. The proposed method offers a reliable motor operation and system performance under steady-state and transient conditions. The simulation works verify the mathematical concept. The simulation results demonstrate that the proposed control method can regulate the motor dynamics while drawing the sinusoidal supply current. © 2022 IEEEÖğe Model Predictive Sliding Surface Control of Voltage Source Inverter(Institute of Electrical and Electronics Engineers Inc., 2022) Gulbudak, O.; Gokdag, M.; Komurcugil, H.This paper presents the model predictive sliding surface control strategy to control the voltage source inverter. The proposed control method benefits from the sliding mode control stability rule to shape the objective function of the optimization problem. The objective function is tailored such that the asymptotic stability criterion is used during the exploration of the optimum control input. The conventional model predictive control method is an effective control routine to handle multiple control goals. However, it can cause closed-loop instability in case of poor selection of the weighting factors or cost function. Due to this unfavorable characteristic of the conventional model predictive control method, the sliding mode control stability criterion is used as a control objective. The proposed objective function formulation guarantees the closed-loop stability regardless of the converter operation points such as power level. The proposed method does not require the weighting factors, which are usually necessary for the applications where the objective function is formed by two or more control goals, thus the system stability is improved. The proposed method is validated by the simulation works, and the results prove the effectiveness of the proposed control method. © 2022 IEEEÖğe A novel sensorless field oriented controller for Permanent Magnet Synchronous Motors(Institute of Electrical and Electronics Engineers Inc., 2014) Aygun, H.; Gokdag, M.; Aktas, M.; Cernat, M.In this paper, a Particle Swarm Optimization based PI controller (PSO-PI) is used for control the speed and the torque of a Permanent Magnet Synchronous Motor (PMSM) while a Model Reference Adaptive System (MRAS) based on an Artificial Neural Network (ANN) estimation mechanism is applied to estimate sensorless the speed. In order to show the capability of the proposed PSO-PI controller, it is compared with a Fuzzy-Logic PI controller and with a classical PI controller. The simulation results prove the usefulness of the proposed PSO-PI controller. © 2014 IEEE.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 Pipelining Strategies and Design Considerations of Predictive Current Control Method(TUBITAK, 2022) Gulbudak, O.; Gokdag, M.This paper explores the pipelining strategies for the model predictive control methods. The array and vector processing methods are examined to discover their applicability in the model predictive current method. The potential benefits of the pipelining methods are investigated, and their design methodologies are scrutinized. The model predictive control is a nonlinear control technique that predicts the system dynamics. The model predictive control (MPC) provides rapid response to the load variations and guarantees robust operation. However, the lower sampling period is the main design constraint to achieve a reliable system operation. The selection of a low sampling period demands a powerful digital controller due to the increasing computational burden. To handle the high calculation burden, a field-programmable gate array (FPGA) is a powerful solution. A proper pipelining strategy enables the use of the MPC in real-time applications. In this paper, pipelining strategies and practical design considerations of the FPGA-based predictive current method are presented. The nine switch converter (NSC) is selected as an experimental case study. The experimental results are provided to demonstrate the theoretical framework. The experimental results prove the feasibility of the array processing and vector processing methods in MPC applications. © 2022, TUBITAK. All rights reserved.Öğe Predictive Current Control Method with State Observer for Grid-Connected Inverter Equipped with LCL-Filter(Institute of Electrical and Electronics Engineers Inc., 2021) Gulbudak, O.; Gokdag, M.This paper presents a predictive control strategy for a grid-connected voltage source inverter with an LCL filter. A full-state observer is used to estimate the LCL filter capacitor voltage to reduce the sensing component. The estimated capacitor voltage is used by the proposed predictive control method. The LCL filter model and converter model are used to predict the control goals. The objective function without the weighting factor is formulated to form the optimal control problem. The proposed control strategy offers an excellent steady-state and transient performance. Design steps for the state estimator and the proposed method are extensively provided. The simulation work validates the theoretical framework. The simulation results confirm that the proposed control method provides a stable grid integration and robust energy conversion process. The theoretical expectations are verified by the simulation-based case studies. © 2021 IEEE.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.Öğe Sliding Mode Current Control Strategy for Nine-Switch Converter(Institute of Electrical and Electronics Engineers Inc., 2021) Gulbudak, O.; Gokdag, M.; Komurcugil, H.This paper proposes a sliding mode control strategy for regulating dual-load fed by a nine-switch converter. The nine-switch converter consists of two three-phase output terminals, and the nine-switch converter can control dual-loads. The nine-switch converter contains fewer switching devices compared to the two-parallel voltage-source inverters. The nines witch converter offers a more compact ac-drive system where multiple load control is required regarding power stage weight and size. Nevertheless, attaining a fully independent control for individual load is a challenging task. The poor closed-loop design causes an unpleasant circulating current between separate load stages. Therefore, the possibility of the interaction between different load stages is the primary closed-loop design consideration. This study proposes the sliding mode control to obtain a reliable energy conversion operation method for a dual output nine-switch converter. Sliding mode control methodology is comprehensively explained, and solid design steps are provided. The simulation work verifies the theoretical framework of the designed sliding mode controller. The performed simulation works demonstrate that multiple ac loads are well regulated by the proposed control method. © 2021 IEEE.
