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Analysis of a Multilevel Inverter Topology with Reduced Number of Switches
(SPRINGER, 2014) Karaca, Hulusi
Multilevel inverter is energy conversion device that is generally used in medium-voltage and high-power applications. It offers lower total harmonic distortion, switching losses and voltage stress on switches than conventional inverter. In this chapter, the topologies of the conventional multilevel inverters are discussed and a novel multilevel inverter topology with the reduced number of power switches is proposed. Also, a modulation technique for the proposed multilevel inverter is introduced. This multilevel inverter structure consists of the level module units to enhance the level of the output voltage. Since a level module unit consists of only a DC voltage source and a bidirectional switch, this structure allows a reduction of the system cost and size. Effectiveness of the proposed topology has been demonstrated by analysis and simulation.
Control of Venturini Method Based Matrix Converter in Input Voltage Variations
(INT ASSOC ENGINEERS-IAENG, 2009) Karaca, Hulusi; Akkaya, Ramazan
Matrix converter is a single-stage converter which directly connects a three-phase voltage source to a three-phase load without dc-link components. Therefore, any harmonic distortion and imbalance in input voltage directly reflect to the output of the converter. Recently, many researchers have made an effort to cope with this problem. In this paper, under distorted input voltage conditions, behaviors of the MC controlled with Venturini method are analyzed and a PI controller based compensation method to prevent negative effects of input voltage is proposed. Since the proposed method is based on closed loop control of the output currents, it not only reduces the output harmonic contents but also ensures a stable control of the load currents. Some results are presented to prove the effectiveness of the proposed compensation technique.
Distorsiyonlu giriş gerilimlerinde UVM kontrollü matris dönüştürücünün performansının iyileştirilmesi
(Selçuk Üniversitesi Fen Bilimleri Enstitüsü, 2010-09-28) Karaca, Hulusi; Akkaya, Ramazan
Elektrik gücünün farklı formlara dönüştürülmesi, güç elektroniğinin en önemli konusudur. Dönüştürme işlemlerinin en önemlilerinden birisi AC-AC dönüştürücüler tarafından gerçekleştirilen güç dönüşümüdür. Bu dönüştürücülerde genellikle sabit genlik ve frekanslı AC gerilim, önce DC gerilime daha sonra tekrar farklı frekans ve genlikli AC gerilime dönüştürülmektedir. Son yıllarda, geleneksel AC-AC güç dönüştürücülerinin yerini almaya aday olan ve doğrudan AC-AC güç dönüşümü yapabilen matris dönüştürücüler üzerine yoğun çalışmalar yapılmaktadır. Bu teknoloji, geleneksel inverter temelli dönüştürücülerde kullanılan reaktif enerji depolama elemanlarına (büyük boyutlu C ve L) olan ihtiyacı ortadan kaldırdığından küçük boyutlu dönüştürücüler tasarlanabilmektedir. Ayrıca iki yönlü anahtarlar kullanılmasından dolayı şebekeye enerji geri dönüşümü yapılabilmektedir. Matris dönüştürücünün diğer önemli özellikleri ise, giriş ve çıkış akımlarının sinüzoidal olması, yükten bağımsız bir şekilde güç faktörünün ayarlanabilmesi ve dört bölgeli çalışmaya izin vermesidir. Ancak bu özelliklerinin yanında matris dönüştürücüler, AC-DC-AC dönüştürücülere göre daha çok güç anahtarına ihtiyaç duyması, karmaşık anahtarlama yapısına sahip olması, maksimum çıkış geriliminin giriş geriliminin %86,6'sı ile sınırlı olması ve şebeke tarafındaki herhangi bir bozukluğun doğrudan çıkışa yansıması gibi dezavantajlara sahiptir. Bu tez çalışmasında, öncelikle matris dönüştürücünün yukarıda bahsedilen dezavantajlarının üstesinden gelebilmek için Uzay Vektör Modülasyonu (UVM) metoduyla kontrol edilen bir matris dönüştürücünün simülasyonu yapılmış ve daha sonra sabit genlik ve frekanslı üç fazlı şebekeden değişken genlik ve frekansta üç fazlı AC çıkış gerilimleri elde etmek için TMS320F2812 sayısal işaret işlemcisi kullanılarak UVM metoduyla kontrol edilen bir matris dönüştürücü pratik olarak gerçekleştirilmiştir. Bu dönüştürücünün simülasyon ve deneysel sonuçlarının uyum içinde olduğu görülmüştür. Ayrıca giriş gerilimindeki bozukluğun çıkışa yansımasını azaltmak ve sistemin çıkış performansını iyileştirmek için iki adet yeni kompanzasyon metodu önerilmiştir. Bunların ilki, bulanık mantık kontrolör temelli geri beslemeli kompanzasyon metodu; diğeri ise, literatürde adı geçen ileri beslemeli kompanzasyon metodu ile önerdiğimiz bulanık mantık temelli kompanzasyon metodunun birlikte kullanıldığı hibrid kompanzasyon metodudur. Önerilen kompanzasyon metotlarının etkinliğini göstermek için 100 Hz'e kadar tüm çıkış frekanslarında matris dönüştürücünün çıkış akımının toplam harmonik distorsiyonları (THD) ölçülmüş ve elde edilen sonuçlar, kompanzasyonsuz ve ileri beslemeli kompanzasyon metotlarının sonuçları ile karşılaştırılmıştır. Önerilen metotların distorsiyonlu giriş gerilimi koşulları altında, matris dönüştürücünün çıkış akımında meydana gelen harmonikleri önemli ölçüde azalttığı ve sistemin çıkış performansını iyileştirdiği gerçekleştirilen simülasyon çalışmalarıyla doğrulanmıştır.
Dynamic Simulation of SVM Based Direct AC/AC Converter
(IEEE, 2014) Karaca, Hulusi; Akkaya, Ramazan
In this study, direct AC/AC converters controlled with space vector modulation (SVM) method are modelled in Matlab&Simulink. Direct AC/AC converters produce directly the three-phase load voltages which have variable frequency and variable amplitude, without rectifying the fixed three-phase input voltages. Simulation results are analyzed for output voltages with various frequency and amplitude.
An Experimental Study of Grid Tied Inverter for Renewable Energy Systems
(IEEE, 2018) Sevilmis, Fehmi; Karaca, Hulusi
Nowadays, electrical energy produced from the renewable energy sources (RES) tends to increase day by day to meet the increasing energy demand. Also, RES enable energy to be obtained more economically and cleanly. Electrical energy based on the RES is preferred to transfer to electrical grid instead of storing. However, this energy is not transferred to the grid directly because of usability and efficiency. Therefore, grid tied inverter which is transferred electrical energy to the grid is used and inverter control mechanism is so important. On the other hand, the inverter output voltages must be synchronized with grid voltages. So, the phase angle and amplitude of the grid voltages must be obtained accurately and fast. To achieve a suitable grid synchronization, phase locked loops (PLL) are widely used. In this paper, a three-phase space vector pulse width modulation (SVPWM) controlled grid tied inverter is simulated in MATLAB/Simulink and implemented with TMS320F28335 DSP. All simulation and experimental results confirm that the output voltages of the grid tied voltage source inverter are compatible with the grid and grid synchronization is successfully achieved thanks to the PLL algorithm.
GA based selective harmonic elimination for Five-level inverter using cascaded H-bridge modules
(2016) Bektas, Enes; Karaca, Hulusi
Multilevel inverters (MLI) have been commonly used in industry especially to get quality output voltage in terms of total harmonic distortion (THD). In addition, development in semiconductor technology and advanced modulation techniques make MLI implementation more attractive. Selective Harmonic Elimination (SHE) that can be applied MLI at desired switching frequency offers elimination of harmonics in the output voltage. Also, by using SHE technique with cascaded H-bridge multilevel inverters, the necessity of using filter in the output can be minimized. In this paper, SHE equations have been solved by using of Genetic Algorithm (GA) Toobox&Matlab and it has been aimed to eliminate desired harmonic orders at fundamental output voltage. Simulation results have clearly demonstrated that GA based SHE techniques can eliminate the demanded harmonic orders.
GA Based Selective Harmonic Elimination for Multilevel Inverter with Reduced Number of Switches
(INT ASSOC ENGINEERS-IAENG, 2015) Karaca, Hulusi; Bektas, Enes
Multilevel inverters have been used in the power applications to get low total harmonic distortion (THD) in medium or high voltage levels. In order to get low THD in the output voltage, several techniques have been applied to multilevel inverter. One of these techniques is Selective Harmonic Elimination (SHE) that has an extensive research area in the field of power electronics. It is also an alternative to usual PWM techniques and includes nonlinear equations of stepped voltage waveform. In this paper, multilevel inverter with reduced number of switches which enables a reduction in the system cost has been proposed, and solution of SHE equations have been optimized by Genetic Algorithm (GA). The results of simulation and analysis have apparently proved that proposed GA based SHE technique eliminates desired harmonic order.
Modelling and simulation of matrix converter under distorted input voltage conditions
(ELSEVIER SCIENCE BV, 2011) Karaca, Hulusi; Akkaya, Ramazan
Matrix converter is an energy conversion device which directly connects a three-phase voltage source to a three-phase load without dc-link components. Therefore, the output of the matrix converter is directly affected by the disturbance or imbalance in the input voltages. Many researchers have made an effort to overcome this problem in recent years. In this paper, the behaviors of the matrix converter controlled with the optimum-amplitude Venturini method are investigated and a novel compensation technique based on fuzzy logic controller is proposed to eliminate the undesirable influences of the input voltage under the distorted input voltage conditions. The proposed technique is based on closed loop control of the three-phase output current to enhance the output performance of the matrix converter. The mathematical model of the proposed system is developed. The simulation of the development model is performed in Matlab&Simulink. Some results demonstrating validity of the proposed compensation technique are presented. (C) 2010 Elsevier B.V. All rights reserved.
A New Bridgeless Multilevel Inverter Structure with Reduced Number of Power Switches
(IEEE, 2017) Bektas, Enes; Bayindir, Kamil Cagatay; Karaca, Hulusi
Multilevel inverter (MLI) has been a different alternative instead of traditional two level inverters and commonly used to obtain quality output voltage with lower Total Harmonic Distortion (THD). In addition, outstanding advantage of MLI is reduced voltage stress of the power switches. However, the structure of MLI needs excessive number of power switches especially for the higher level inverter that supplies lower THD value and lower voltage drop on the semiconductor switches. In this paper, new bridgeless multilevel inverter structure with reduced number of power switches has been proposed. Additionally, the working operations of proposed MLI have been analyzed. Harmonic Minimization Pulse Width Modulation (HMPWM) technique has been applied to proposed MLI and simulation results have been obtained by using Simulink&MATLAB. Simulation results have clearly proved that proposed new MLI's structure can be operated with resistive and inductive load and generate waveform output voltage of traditional MLI by using less number of power switches.
A Novel Compensation Method Based on Fuzzy Logic Control for Matrix Converter under Distorted Input Voltage Conditions
(IEEE, 2009) Karaca, Hulusi; Akkaya, Ramazan; Dogan, Hueseyin
Matrix converter (MC) is a direct energy conversation device without de-link components. Therefore, the output of the converter is directly affected by the disturbances in the input voltages. Many researchers have made an effort to overcome this problem. In this paper, the behaviors of the MC have been investigated under the distorted input voltage conditions. A fuzzy logic control (FLC) based novel compensation method is proposed, which performs close loop control of the output current to improve the output performance of the MC. Some results are presented to prove the effectiveness of the proposed compensation technique.
A Novel Hybrid Compensation Method Reducing the Effects of Distorted Input Voltages in Matrix Converters
(KAUNAS UNIV TECHNOLOGY, 2019) Karaca, Hulusi; Akkaya, Ramazan
Matrix converters have the most compact and efficient AC-AC converter structure due to the lack of the DC intermediate components. The matrix converter makes a single-stage conversion directly connecting any terminal of voltage source to any terminal of load. This outstanding feature leads to some problems that must be overcome under the distorted input voltage conditions. A matrix converter has low immunity to power source disturbances, because it has no DC intermediate circuit. Any disturbance in the power source creates a negative effect on the load of the matrix converter and on the current drawn from the source. In this study, a novel compensation method, which provides immunity against input voltage disturbances, is suggested for the matrix converter. The suggested method has a hybrid structure, which includes both feedforward and fuzzy logic controller based feedback methods. The effectiveness and accuracy of the suggested new hybrid compensation approach are proved by the various results obtained.
A Novel Topology for Multilevel Inverter with Reduced Number of Switches
(INT ASSOC ENGINEERS-IAENG, 2013) Karaca, Hulusi
Multilevel inverter is energy conversion device that is generally used in medium-voltage and high-power applications. It offers lower total harmonic distortion, switching losses and voltage stress on switches than conventional inverter. In this paper, a novel multilevel inverter topology with the decreased number of power switches is proposed, and its modulation technique is introduced. This multilevel inverter structure consists of the level module units to enhance the level of the output voltage. Since a level module unit consists of only a DC voltage source and a bidirectional switch, this structure allows a reduction of the system cost and size. Effectiveness of the proposed topology has been demonstrated by analysis and simulation.
PIC mikrodenetleyici kullanılarak fırçasız DC motorun sensörsüz kontrolü
(Selçuk Üniversitesi Fen Bilimleri Enstitüsü, 2004-07-23) Karaca, Hulusi; Akkaya, Ramazan
Bu çalışmada, Sürekli Mıknatıslı Fırçasız DC Motorların sensörsüz kontrol teknikleri incelenerek motorların yapısı, çalışma prensipleri, çeşitleri, sürücüleri ve mıknatıslan hakkında geniş bilgi verilmiş ve zıt emk integrasyonu metodu kullanılarak bir fırçasız DC motorun sensörsüz kontrolü pratik olarak gerçekleştirilmiştir. Gerçekleştirilen sistemde, geri besleme için zıt emk integrasyonuna göre kontrol sinyalleri üreten ML4425 tümdevresi kullanılmıştır. Ayrıca motor hızının sürekli durum hatasını sıfırlamak ve daha hızlı cevap süresi elde etmek için PIC16F877 mikrodenetleyicisi kullanılarak sisteme bir oransal- integral (PI) dış kontrol çevrimi ilave edilmiştir. ML4425 tümdevresi, inverteri kontrol etmek için zıt emk gerilimlerine göre rotor pozisyonuna uygun anahtarlama sinyalleri ve hız geri beslemesi olarak kullanılmak üzere de frekansı, motor hızıyla orantılı kare dalga bir sinyal üretmektedir. Frekansı hız ile orantılı sinyalden motorun gerçek hızı hesaplanmıştır. Gerçek hız ile referans hız arasındaki hata sinyalinin, sayısal bir PI kontrol algoritmasından geçirilmesiyle elde edilen çıkış sinyali, ML4425 tüm devresinin kontrol ucuna uygulanmıştır. Sistemin maliyetini ve kullanılan eleman sayısını düşürmek için üç fazlı inverter devresinde üst anahtar olarak P kanallı MOSFET'ler tercih edilmiştir. Böylece ilave MOSFET sürme elemanlarının kullanılmasına gerek kalmamıştır.
Selective Harmonic Elimination Using Genetic Algorithm for Multilevel Inverter with Reduced Number of Power Switches
(NEWSWOOD LTD, 2016) Karaca, Hulusi; Bektas, Enes
Multilevel inverters have been widely used in the power applications to get low total harmonic distortion (THD) in medium or high voltage levels. There have been several techniques that can be applied to multilevel inverter so as to get low THD in the output voltage. Selective Harmonic Elimination (SHE) technique is one of these techniques and also has an extensive field of applications in power electronics. It is also an alternative to usual PWM techniques and includes nonlinear equations of stepped voltage waveform. In addition, SHE technique offers to control effective value of output voltage. In this paper, multilevel inverter with reduced number of switches which enables a reduction in the system cost has been proposed, and solution of nonlinear SHE equations have been optimized by Genetic Algorithm (GA) software. The results of simulation and analysis have clearly demonstrated that proposed GA based SHE technique can eliminate desired harmonic order.
Simulation and Analysis of SVPWM Based VSI for Wind Energy Systems
(IEEE, 2014) Sevilmis, Fehmi; Karaca, Hulusi
Space Vector Pulse Width Modulation (SVPWM) technique is extensively used to control the three-phase voltage source inverter (VSI) of wind energy systems. The main advantages of SVPWM method are fixed switching frequency, low harmonic content and higher DC bus utilization. In terms of the use of the DC bus voltage compared to conventional PWM method provides 15.15% more efficient usage. This paper focuses on SVPWM controlled three-phase VSI simulated under MATLAB/SIMULINK.
Simulation of Three-Phase Grid Interactive Inverter for Wind Energy Systems
(IEEE, 2015) Sevilmis, Fehmi; Karaca, Hulusi
Electrical energy's transfer, obtained from the wind energy systems, directly to the grid or load is not possible in terms of efficiency and usability. For these reasons, grid interactive inverters are largely used for wind energy systems. In this study, three phase grid interactive Voltage Source Inverter (VSI) controlled by Space Vector Pulse Width Modulation (SVPWM) has been performed. The current controller model, Proportional-Integral (PI) controller regulated the injected grid current, has been implemented as the grid interactive VSI control model. In order to operate between inverter and grid synchronously, the phase angle of grid voltage is detected by using Phase Locked Loop (PLL) in dq-synchronous reference frame. This system has been simulated under MATLAB/SIMULINK. Simulation results illustrate that inverter output voltages are in same phase and frequency with grid voltages.

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