WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394
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Conference Object Citation - WoS: 5Citation - Scopus: 5Design and Control of a Single Phase DC/Rectified AC/AC Inverter for Low THD Applications(Institute of Electrical and Electronics Engineers Inc., 2018-10) Tekgun, Burak; Tekgun, Didem; Alan, İrfan; Badawy, Mohamed O.In this paper, a single phase DC/Rectified AC/AC (DC/RAC/AC) inverter is analyzed and compared to classical single phase PWM inverters. A traditional AC power supply (PS) system consists of a DC/DC converter, a cascaded H-bridge inverter, and a passive filter to generate the sinusoidal output voltage. The presented DC/RAC/AC inverter has a similar structure; however, the control of the cascaded units differ. The presented method generates rectified sine wave at the output of the DC/DC converter unit and the H-bridge inverter alternates the rectified sine wave to generate the full sine wave without having an additional output filter; hence, the switching losses at the H-bridge inverter is limited to the line frequency (50-60 Hz). Moreover, the bulk DC bus capacity at the output of the DC/DC converter is reduced significantly. Therefore, the power consumed by the passive elements are minimized. The circuit modes of operation are analyzed and the system is simulated in Matlab/Simulink environment for both traditional and proposed topologies. Results show that the proposed system is superior to the traditional one in terms of efficiency, generated THD with a simplified control structure, and it offers a reduced system size and cost. © 2019 Elsevier B.V., All rights reserved.Article Citation - WoS: 4Citation - Scopus: 4Bright Green and Blue Solid-State Emitting Carbon Dots With Optimized Photoluminescence Characteristics for Fabrication of High-Performance Light Emitting Diodes(Elsevier Sci Ltd, 2025-09) Havasi, Nasrin; Sahraei, Reza; Soheyli, Ehsan; Lan, Yu; Lou, Qing; Houshmand, Fatemeh; Shan, Chong-XinLuminescent carbon dots (CDs) possess a range of fundamental and technological advantages, including low-cost, and scalable preparation methods, high emission efficiency, tunable electronic properties, and adaptable surface characteristics. However, aggregation-caused quench in solid-state emission of CDs has constrained their applications in luminescent solar-concentrators, and light-emitting devices. This study introduces a rapid and straightforward microwave method for producing bright blue-and green-emissive CDs, with emission peaks at 440 nm and 520 nm, respectively. Blue-CDs showed excitation-dependent feature with a biexponential decay profile and average lifetime of 6.3 ns, while the green one signified an excitation-independent photoluminescence profile with longer average lifetime of 9 ns through biexponential fitting of decay plot. Upon optimization of experimental parameters, reproducible green emission with a high efficiency of 78 % was achieved in dimethyl sulfoxide (DMSO). The critical role of biurea as a nitrogen precursor was elucidated through experimental and computational investigations. Furthermore, owing to the bright solid-state emission of the synthesized CDs, they were utilized as color-converting layers in the fabrication of durable monochrome LEDs, yielding blue and yellowish-green emissions with Commission Internationale de L'E<acute accent>clairage (CIE) coordinates of (0.16, 0.10) and (0.35, 0.57), respectively. This study highlights the potential of CDs for applications in light-emitting panels.Conference Object Citation - WoS: 3Citation - Scopus: 3A Modular Three-Phase Buck-Boost Motor Drive Topology(IEEE, 2020-10-05) Tekgun, Didem; Tekgun, Burak; Alan, IrfanThe voltage-source inverter (VSI) is a fundamental power electronic device to drive three-phase electrical machines with high performance. In this paper, a modular three-phase DC/Rectified AC/AC (DC/RAC/AC) inverter supplying a permanent-magnet synchronous machine (PMSM) is proposed. In this topology, the three-phase VSI is composed of three single-phase modules connected in parallel. Each single-phase inverter module consists of a non-inverting bidirectional buck-boost DC/DC converter and a cascaded H-bridge inverter. Here, the DC/DC converter generates rectified AC waveforms and the H-bridge inverter alternates these signals to create the intended AC voltage waveform. Therefore, the bulk DC Bus capacitor and boost converter inductor, which exist in a typical battery-powered voltage boosting topology can be eliminated which results in a smaller size and reduced cost. In addition, the switching losses only occur in the DC/DC converter unit and the H-bridge inverter switching losses are negligible due to the zero-voltage switching while in a conventional structure, high-frequency switching occurs both in the DC/DC converter and the six-switch inverter causing reduced overall system efficiency. The proposed inverter is controlled with a well-known field-oriented control (FOC). This paper presents the operating principle, design, and control structure of the proposed three-phase inverter. The functionality of the three-phase inverter is verified through PowerSim simulations. The proposed motor drive system is compared to the conventional one while driving a 4 kW PMSM with FOC and the whole system efficiency difference map is generated. The biggest difference is recorded as 3.8 points favoring the proposed system.