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Javad Ebrahimi

Bio: Javad Ebrahimi is an academic researcher from Queen's University. The author has contributed to research in topics: Capacitor & Voltage. The author has an hindex of 7, co-authored 19 publications receiving 900 citations. Previous affiliations of Javad Ebrahimi include Amirkabir University of Technology & Isfahan University of Technology.

Papers
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Journal ArticleDOI
TL;DR: A new topology for cascaded multilevel converter based on submultileVEL converter units and full-bridge converters is proposed, optimized for various objectives, such as the minimization of the number of switches, gate driver circuits and capacitors, and blocking voltage on switches.
Abstract: In this paper, a new topology for cascaded multilevel converter based on submultilevel converter units and full-bridge converters is proposed. The proposed topology significantly reduces the number of dc voltage sources, switches, IGBTs, and power diodes as the number of output voltage levels increases. Also, an algorithm to determine dc voltage sources magnitudes is proposed. To synthesize maximum levels at the output voltage, the proposed topology is optimized for various objectives, such as the minimization of the number of switches, gate driver circuits and capacitors, and blocking voltage on switches. The analytical analyses of the power losses of the proposed converter are also presented. The operation and performance of the proposed multilevel converter have been evaluated with the experimental results of a single-phase 125-level prototype converter.

471 citations

Journal ArticleDOI
TL;DR: The proposed topology is based on a cascaded connection of single-phase submultilevel converter units and full-bridge converters and is optimized in order to utilize a minimum number of switches and dc voltage sources and produce a high number of output voltage steps.
Abstract: In this paper, a new topology of a cascaded multilevel converter is proposed. The proposed topology is based on a cascaded connection of single-phase submultilevel converter units and full-bridge converters. Compared to the conventional multilevel converter, the number of dc voltage sources, switches, installation area, and converter cost is significantly reduced as the number of voltage steps increases. In order to calculate the magnitudes of the required dc voltage sources, three methods are proposed. Then, the structure of the proposed topology is optimized in order to utilize a minimum number of switches and dc voltage sources, and produce a high number of output voltage steps. The operation and performance of the proposed multilevel converter is verified by simulation results and compared with experimental results of a single-phase 49-level converter, too.

249 citations

Journal ArticleDOI
TL;DR: A new evolutionary algorithm known as the shuffled frog leaping algorithm is presented, to solve the unit commitment (UC) problem, to minimize the total energy dispatch cost over the scheduling horizon while all of the constraints should be satisfied.
Abstract: A new evolutionary algorithm known as the shuffled frog leaping algorithm is presented in this paper, to solve the unit commitment (UC) problem. This integer-coded algorithm has been developed to minimize the total energy dispatch cost over the scheduling horizon while all of the constraints should be satisfied. In addition, minimum up/down-time constraints have been directly coded not using the penalty function method. The proposed algorithm has been applied to ten up to 100 generating units, considering one-day and seven-day scheduling periods. The most important merit of the proposed method is its high convergence speed. The simulation results of the proposed algorithm have been compared with the results of algorithms such as Lagrangian relaxation, genetic algorithm, particle swarm optimization, and bacterial foraging. The comparison results testify to the efficiency of the proposed method.

173 citations

Journal ArticleDOI
TL;DR: This article proposes a novel three-phase MSI for integration and active control of a high-voltage dc source and a low-voltages dc source that employs a smaller number of semiconductor devices at the current path in various operating modes in comparison to the previously published counterparts, which results in an improved efficiency operation.
Abstract: Multisource inverters (MSIs) as a new approach for the integration of the energy and the power sources in electric vehicle applications have gained considerable attraction. Such structures offer the active control of the dc sources without using any dc/dc converters or magnetic elements, which reduces the weight, and the volume of the power electronics interface between the sources and the load. Moreover, high power density and improved efficiency due to the elimination of the magnetics are the other significant features of an MSI. This article proposes a novel three-phase MSI for integration and active control of a high-voltage dc source and a low-voltage dc source. The proposed MSI structure employs a smaller number of semiconductor devices at the current path in various operating modes in comparison to the previously published counterparts, which results in an improved efficiency operation. Performance of the proposed MSI using a modified space vector modulation technique for all possible operating modes is verified through simulations and experiments on a laboratory prototype

30 citations

Journal ArticleDOI
TL;DR: It is shown that the proposed structure is superior to other FCM-based structures from different standpoints, it reduces the number of high-frequency switches, theNumber of FCs, and at the same time improves the quality of output voltage.
Abstract: This paper presents a new multicell topology based on flying capacitor (FC) structure suitable for multilevel converters. The proposed topology employs the concept of phase-shifted carrier pulse width modulation (PWM) with modified modulating signals to generate appropriate PWM signals. The modulation strategy along with all possible switching states are explained. The implementation of the proposed PWM technique is shown by the help of illustrating waveforms. To show the advantages of the proposed structure, different performance criteria are compared with other FC multicell (FCM) structures. Simulation results are used to further evaluate the potential merits of the proposed topology. It is shown that the proposed structure is superior to other FCM-based structures from different standpoints. Specifically, it reduces the number of high-frequency switches, the number of FCs, and at the same time improves the quality of output voltage. A laboratory-type experimental setup is used to validate the modulation strategy and other theoretical findings.

28 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, some of the recently proposed multilevel inverter topologies with reduced power switch count are reviewed and analyzed, both in terms of the qualitative and quantitative parameters.
Abstract: Multilevel inverters have created a new wave of interest in industry and research. While the classical topologies have proved to be a viable alternative in a wide range of high-power medium-voltage applications, there has been an active interest in the evolution of newer topologies. Reduction in overall part count as compared to the classical topologies has been an important objective in the recently introduced topologies. In this paper, some of the recently proposed multilevel inverter topologies with reduced power switch count are reviewed and analyzed. The paper will serve as an introduction and an update to these topologies, both in terms of the qualitative and quantitative parameters. Also, it takes into account the challenges which arise when an attempt is made to reduce the device count. Based on a detailed comparison of these topologies as presented in this paper, appropriate multilevel solution can be arrived at for a given application.

890 citations

Journal ArticleDOI
TL;DR: In this article, the principle of modularity is used to derive the different multilevel voltage and current source converter topologies for high-power dc systems, where the derived converter cells are treated as building blocks and are contributing to the modularity of the system.
Abstract: In this paper, the principle of modularity is used to derive the different multilevel voltage and current source converter topologies. The paper is primarily focused on high-power applications and specifically on high-voltage dc systems. The derived converter cells are treated as building blocks and are contributing to the modularity of the system. By combining the different building blocks, i.e., the converter cells, a variety of voltage and current source modular multilevel converter topologies are derived and thoroughly discussed. Furthermore, by applying the modularity principle at the system level, various types of high-power converters are introduced. The modularity of the multilevel converters is studied in depth, and the challenges as well as the opportunities for high-power applications are illustrated.

883 citations

Journal ArticleDOI
TL;DR: Two new topologies are proposed for multilevel inverters that reduce the number of switches and isolated dc voltage sources, the variety of the dc voltage source values, and the size and cost of the system in comparison with the conventional topologies.
Abstract: In this paper, two new topologies are proposed for multilevel inverters. The proposed topologies consist of a combination of the conventional series and the switched capacitor inverter units. The proposed topologies reduce the number of switches and isolated dc voltage sources, the variety of the dc voltage source values, and the size and cost of the system in comparison with the conventional topologies. In addition, the proposed topologies can double the input voltage without a transformer. There is no need for complicated methods to balance the capacitor voltage. The simulation and experimental results of single-phase 25- and 17-level inverters are given to prove the correct operation of the proposed topologies.

389 citations

Journal ArticleDOI
TL;DR: A multilevel inverter that has been conceptualized to reduce component count, particularly for a large number of output levels, is presented, which results in reduced number of power switches as compared to classical topologies.
Abstract: This paper presents a multilevel inverter that has been conceptualized to reduce component count, particularly for a large number of output levels. It comprises floating input dc sources alternately connected in opposite polarities with one another through power switches. Each input dc level appears in the stepped load voltage either individually or in additive combinations with other input levels. This approach results in reduced number of power switches as compared to classical topologies. The working principle of the proposed topology is demonstrated with the help of a single-phase five-level inverter. The topology is investigated through simulations and validated experimentally on a laboratory prototype. An exhaustive comparison of the proposed topology is made against the classical cascaded H-bridge topology.

353 citations

Journal ArticleDOI
TL;DR: The objective of this paper is to propose a new inverter topology for a multilevel voltage output based on a switched capacitor technique, which is not only very simple and easy to be extended to a higher level, but also its gate driver circuits are simplified because the number of active switches is reduced.
Abstract: The objective of this paper is to propose a new inverter topology for a multilevel voltage output. This topology is designed based on a switched capacitor (SC) technique, and the number of output levels is determined by the number of SC cells. Only one dc voltage source is needed, and the problem of capacitor voltage balancing is avoided as well. This structure is not only very simple and easy to be extended to a higher level, but also its gate driver circuits are simplified because the number of active switches is reduced. The operational principle of this inverter and the targeted modulation strategies are presented, and power losses are investigated. Finally, the performance of the proposed multilevel inverter is evaluated with the experimental results of an 11-level prototype inverter.

349 citations