Browsing by Author "Iskender, I."

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Application of Interleaved Bridgeless Boost Pfc Converter Without Current Sensing
(IEEE Computer Society, 2014) Genc, N.; Iskender, I.; Celik, M.A.
Interleaved bridgeless boost power factor correction (PFC) converter based on predictive control method without any current sensing is presented in this paper. Complicated control strategies including current sensing are used to obtain proper current sharing and current ripple minimization for interleaved type PFC converters which are more suitable than the conventional type PFC converters by virtue of the improving power rating and reducing input current ripple. The proposed predictive control method doesn't need to sample any current signals, only the samplings of the input voltage and the output voltage are required. The input current of the converter is computed based on the input and output voltages according to the switching operations. The duty cycle for next switching is predicted by using reference current signal obtained from the voltage loop compensator, computed input current and converter parameters. A prototype of interleaved bridgeless boost PFC converter controlled by a digital signal processor (DSP) board was established to show the related results. © 2014 IEEE.
Dsp-Based Current Sharing of Average Current Controlled Two-Cell Interleaved Boost Power Factor Correction Converter
(inst Engineering Technology-iet, 2011) Genc, N.; Iskender, I.
Power factor correction (PFC) pre-regulators are used between the ac line and non-linear load to improve the line current in terms of power factor and total harmonic distortion (THD). In medium-and high-power applications, the interleaved boost PFC converter is the proper solution for this purpose to obtain a pre-regulator with lower size. The operation of the interleaved boost PFC converter provides a reduction of the inductor and electromagnetic interference filter volumes compared with those of the conventional single switch boost PFC converter. However, proper current sharing and current ripple minimisation must be ensured to achieve these benefits. The current sharing between cells of a two-cell interleaved boost PFC converter, which is an important problem in applications is analysed and discussed in this study and the problem is removed by using a digital signal processing (DSP)-based simple practical solution. The proposed technique provides the proper current sharing by sensing only the rectifier output current (total current of cells) without using any external control loop. The simulation and the experimental results are presented to show the validity.
Dynamic Behavior of Dc-Dc Boost Converter Controlled With Cascade Pi-Asc
(Institute of Electrical and Electronics Engineers Inc., 2017) Genc, N.; Uzmus, H.; Iskender, I.
This paper deals with controlling DC-DC boost converter by average sliding controller (ASC) cascaded with PI voltage controller. In the study after modeling of circuit configuration, the cascaded PIASC controller is applied to the DC-DC Boost converter. The output value of PI voltage controller is used as a reference current value for ASC which is used for current controller. The topology is modeled and simulated in MATLAB/Simulink program under variable load. Then the simulation results of the PIASC controller are compared to that of PI-PI controller. © 2016 IEEE.
Evaluating and Derating of Three-Phase Distribution Transformer Under Unbalanced Voltage and Unbalance Load Using Finite Element Method
(IEEE Computer Society, 2014) Njafi, A.; Iskender, I.; Genc, N.
Power transformers illustrate the majority of capital investment in transmission and distribution centers. Additionally, interruptions of power transformer have a significant economic Effects on the Performance of an electrical network. For this reason, the safe and reliable Performance relate directly to the Security and stability of power system. This paper studies the growth of power losses and Derating of Distribution transformer, working under unbalance voltage and unbalanced load conditions. In this paper, computer-based simulation utilizing the two and three dimensional finite element methods (3-D and 2-D FEM) are exploited as a tool for visualizing magnetic fields of distribution transformers. Finite Element Method (FEM) is one among popular numerical methods that is able to handle problem complexity in various forms. The performance of the transformer when the load and supply are balanced compared to the case in which voltage or load is unbalanced indicates that the unbalanced load only causes the copper loss to increase, while the unbalanced voltage not only increases copper loss but also adds to the core loss. The indices of voltage unbalance factor (VUF) are used in this paper to evaluate the unbalance propagation. This process enables the software to simulate and analyze different electromagnetic parameters such as magnetic flux lines, flux density, losses, and etc, under different input sources with high accuracy. © 2014 IEEE.
Impact of Environmental Factors on Photovoltaic Systems
(Nova Science Publishers, Inc., 2012) Iskender, I.; Abdulazeez, M.Z.; Genc, N.
Photovoltaic (PV) modules are sensitive to environmental factors such astemperature, irradiance and shading. Therefore, the impacts of environmental factors onphotovoltaic systems are investigated in this chapter. Generally, the PV modules getshadowed, completely or partially, by the passing clouds, neighboring buildings andtowers, trees, and utility and telephone poles. The situation is of particular interest in caseof large PV installations such as those used in distributed power generation schemes.Under partially shaded conditions, the PV characteristics get more complex with multiplepeaks. Therefore, except for temperature and irradiance, the impact of partial shadingcaused by clouds and other neighbor objects on the performance of photovoltaic systemsare investigated. Developing of photovoltaic market and the electrical models of solarcells will be analyzed and discussed. In addition, shading effects on photovoltaic panelsare studied with simulation and experimental results. Some implementations ofphotovoltaic systems are given end of the chapter. © Nova Science Publishers, Inc.
Power Quality Improvement Using Active Ac/Dc Pfc Converters
(Nova Science Publishers, Inc., 2012) Iskender, I.; Genc, N.
Most modern electrical and electronic apparatus called as nonlinear loads use AC/DC power supply within their architecture. These devices draw discontinuous current from the AC network. The discontinuous currents include harmonics and cause problems for the power distribution systems. In addition, the harmonic contents of the discontinuous current cause additional losses and dielectric stresses in capacitors and cables resulting in increasing currents in windings of rotating machinery, transformers and electromagnetic interference. With the steadily increasing use of equipments including nonlinear loads, line current harmonics have become a significant problem. So, several international standards such as EN 61000-3-2 now exist limiting the harmonic content due to line currents of equipment connected to AC networks. In this chapter, parallel to power factor correction (PFC) study, several passive and active topologies applied to single phase power factor correction are analyzed. The major advantages and disadvantages of the topologies are highlighted. In addition, the commonly used control methods for active power factor correction are discussed and compared. The switching losses and soft switching methods of the boost type active power factor correction circuits are also reviewed and discussed. In the several active power factor correction techniques used to reduce current harmonics and to satisfy the requirements given in international standards, the boost type converters operating in continuous conduction mode have been widely adopted as power factor correction pre-regulators. For this purpose, the boost type power factor correction circuit is simulated and the related waveforms are given to show the importance of active power factor correction methods. © 2011 Nova Science Publishers, Inc.
Sensorless Speed Control of a Bldc Motor Using Improved Sliding Mode Observer Technique
(International Organization on 'Technical and Physical Problems of Engineering', 2019) Topal, M.; Iskender, I.; Genc, N.
This paper proposes controlling the velocity of BLDC motor using sliding mode observer technique based on the estimation of back electromotive force (back EMF). There are many different sensorless control methods for BLDC motor, but in this paper one of them is examined in detail, comparing with the zero crossing points detection of back EMF and hall sensor control. The proposed method estimates the velocity and rotor position by measuring terminal voltages and currents. According to the rotor position, two inverter switches are energized to commutate the phases of BLDC motor. As comparing desired and real line currents, the commutation signals are acquired with hysteresis band. The simulation model of the suggested method is performed by using MATLAB Simulink environment and results have been simulated to interrogate the performance of the BLDC motor under a load change condition also with reference speed. © 2019, International Organization on 'Technical and Physical Problems of Engineering'. All rights reserved.