Browsing by Author "Karaca, Hulusi"

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DSTATCOM Tabanlı KUAG Sistemlerinde Gerilim Regülasyonu için DQ ve CSD Yöntemlerinin Karşılaştırmalı Çalışması
(2025) Özer, Ali Sait; Karaca, Hulusi
Kendinden Uyarımlı Asenkron Generatör (KUAG), bağımsız güç üretim sistemlerinde, önemli bir rol oynamaktadır. SEIG'ler yük koşulları değiştiğinde terminal gerilimini korumakta zorluk çektiği için etkili bir kompanzasyon ve kontrol sistemine ihtiyaç duyulmaktadır. Dağıtım Statik Kompanzatörleri (DSTATCOM) hızlı dinamik tepkileri, reaktif güç desteği ve harmonik azaltma yetenekleri ile ön plana çıkmaktadır. DSTATCOM'ların performansı kontrol yönteminin etkinliğine bağlıdır. Bu çalışmada, yaygın olarak kullanılan dq yöntemi ile Akım Senkron Algılama (CSD) yönteminin performansı doğrusal olmayan yükler, dengesiz yükler ve DC ofset koşulları altında karşılaştırılmıştır. CSD yöntemi, PCC gerilimlerini filtrelemedeki etkinliği, tepe değerini tahmin etmesi ve basit algoritması ile öne çıkmaktadır. Ayrıca akım ve gerilimlerde meydana gelen DC ofset durumlarında faz gerilimi kestirimi daha üstündür. dq yönteminde ise faz senkronizasyonundaki yüksek doğruluk ve kararlılığı sayesinde harmonik bastırma, akım ve gerilim dengeleme ve DC ofset etkilerini azaltmada başarılı performans sağlamıştır. Her iki yöntemde de IEEE-519 standartlarına uygun şekilde SEIG akım ve geriliminin toplam harmonik distorsiyonu (THD) %5'in altındadır.
Citation - WoS: 9
Citation - Scopus: 11
Enhanced Control Method for Voltage Regulation of Dstatcom Based Seig
(Elsevier, 2022) Özer, Ali Sait; Sevilmiş, Fehmi; Karaca, Hulusi; Arabacı, Hayri
Self-excited induction generator (SEIG)-based wind energy conversion systems (WECS) are very popular for feeding standalone loads in remote areas where there is no grid. SEIG needs adjustable reactive power to regulate terminal voltage and frequency. Usually, a combination of a distributed static compensator (DSTATCOM) and a fixed capacitor bank is used to meet this reactive power demand. DSTATCOM is the most suitable option for power quality compensation. The performance of DSTATCOM depends on its control algorithm that generates the proper switching signals for voltage source inverter (VSI). Many control algorithms have been proposed for DSTATCOM in the literature. Among them, the most frequently used algorithms are synchronous reference frame (SRF), instantaneous reactive power (IRP), and current synchronous detection (CSD) algorithms. An effective control algorithm must accurately estimate the amplitude of the terminal voltage without being affected by harmonics, DC-offset, and frequency variation. For this purpose, an enhanced phase locked loop (EPLL)-based CSD control algorithm is proposed to estimate the amplitudes of individual phase voltages, and to filter SEIG voltages in case of harmonics, DC offset, and frequency variation. The proposed algorithm has been tested under linear and nonlinear load conditions. The obtained results clearly demonstrate the effectiveness of the proposed EPLL-based CSD control algorithm. (C) 2022 The Author(s). Published by Elsevier Ltd.
Enhanced DSOGI-PLL Based Control Strategy for DSTATCOM
(IEEE, 2025) Ozer, Ali Sait; Karaca, Hulusi
A self-excited induction generator (SEIG) is highly preferred in standalone wind power generation systems due to its robust structure. In order for the voltage and frequency generated by SEIG to be stable and constant, active and reactive power control is required. For this purpose, DSTATCOM is widely used. The effectiveness of the performance of DSTATCOM depends on the control algorithm used. The control algorithm generates reference currents using load currents, SEIG voltages, and frequency. When the SEIG is fed with nonlinear and unbalanced loads, if the load currents are not well filtered, the active components, reactive components, and frequency can be misestimated. In this paper, an enhanced DSOGI-PLL based control algorithm with superior filtering capability is proposed for voltage and frequency control of SEIG. The proposed algorithm is tested under nonlinear load and nonlinear unbalanced load conditions. The results clearly demonstrated the superiority of the EDSOGI-PLLL based algorithm.
Citation - WoS: 2
Citation - Scopus: 2
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.
Performance Comparison of Phase Locked Loop Methods for Grid Interactive Inverters
(Konya Technical University, 2019) Sevilmiş, Fehmi; Karaca, Hulusi
In grid interactive power converter applications, phase locked loop (PLL) methods are very important to realize grid synchronization. The performance of PLL which is used should be affected by adverse conditions such as voltage unbalance, harmonics, frequency and phase changes. Furthermore, in these adverse conditions, the phase angle of grid voltages and positive sequence component of grid voltages in fundamental grid frequency are needed to determine quickly and accurately. Otherwise, synchronization errors occur between the grid interactive inverter and the grid.In this paper, different PLL methods are simulated under MATLAB/Simulink. The performances of the PLL methods are comparatively presented under three different conditions such as unbalanced, harmonics and variable frequency grid. It has also put forward the positive and negative aspects of the PLL methods based on the obtained results.
A Speed Detection Method for Bldc Motor
(IEEE, 2024) Sevilmis, Fehmi; Ozer, Ali Sait; Karaca, Hulusi
It is very important to accurately determine the position and speed of BLDC motor. The use of an encoder to precisely control the motor is a suitable solution, but the placement of the encoder on the motor shaft causes the volume of the system to increase. In addition, the high cost of the encoder is another disadvantage. To overcome these problems, sensorless control algorithms can be used for position and speed detection. However, the complex structure of sensorless control methods and their inadequate performance at low speeds cause them not to he preferred in practical applications. For these reasons, hall-effect sensor control algorithms come to the forefront due to their simple structure and low cost. Since the resolution of hall sensor signals is low, these signals must be processed properly in speed detection. For this purpose, MAF-PLL-based speed detection method is proposed in this study. The proposed method is tested under different conditions. The results obtained show the accuracy of the proposed speed detection algorithm.