Sara Laali

Bio: Sara Laali is an academic researcher from University of Tabriz. The author has contributed to research in topics: Inverter & Topology (electrical circuits). The author has an hindex of 13, co-authored 31 publications receiving 1330 citations. Previous affiliations of Sara Laali include Islamic Azad University South Tehran Branch & Islamic Azad University.

A Single-Phase Cascaded Multilevel Inverter Based on a New Basic Unit With Reduced Number of Power Switches

Abstract: In this paper, a new single-phase cascaded multilevel inverter is proposed. This inverter is comprised of a series connection of the proposed basic unit and is able to only generate positive levels at the output. Therefore, an H-bridge is added to the proposed inverter. This inverter is called the developed cascaded multilevel inverter. In order to generate all voltage levels (even and odd) at the output, four different algorithms are proposed to determine the magnitude of dc voltage sources. Reduction in the number of power switches, driver circuits, and dc voltage sources is the advantage of the developed single-phase cascaded multilevel inverter. As a result, the installation space and cost of the inverter are reduced. These features are obtained by the comparison of the conventional cascaded multilevel inverters with the proposed cascaded topology. The ability of the proposed inverter to generate all voltage levels (even and odd) is reconfirmed by using the experimental results of a 15-level inverter.

A New General Topology for Cascaded Multilevel Inverters With Reduced Number of Components Based on Developed H-Bridge

Abstract: In this paper, a new general cascaded multilevel inverter using developed H-bridges is proposed. The proposed topology requires a lesser number of dc voltage sources and power switches and consists of lower blocking voltage on switches, which results in decreased complexity and total cost of the inverter. These abilities obtained within comparing the proposed topology with the conventional topologies from aforementioned points of view. Moreover, a new algorithm to determine the magnitude of dc voltage sources is proposed. The performance and functional accuracy of the proposed topology using the new algorithm in generating all voltage levels for a 31-level inverter are confirmed by simulation and experimental results.

Cascaded Multilevel Inverter With Series Connection of Novel H-Bridge Basic Units

Abstract: In this paper, a new single-phase cascaded multilevel inverter based on novel H-bridge units is proposed. In order to generate all voltage levels (even and odd) at the output, nine different algorithms are proposed to determine the magnitudes of dc voltage sources. Then, the proposed algorithms are compared to investigate their advantages and disadvantages. This topology is able to increase the number of output voltage levels by using a lower number of power electronic devices such as switches, power diodes, driver circuits, and dc voltage sources that lead to reduction in installation space and cost of the inverter. In addition, in the proposed cascaded multilevel inverter, not only the number of required power electronic devices is reduced, but also the amount of the blocked voltage by switches, and the number of different voltage amplitudes of the used sources is decreased. These features are some of the most important advantages of the proposed topology. These features are obtained via the comparison of the proposed topology and its proposed algorithms with the conventional cascaded multilevel inverters that have been presented in the literatures. The operation and performances of the proposed topology with its presented algorithms in generating all voltage levels have been verified by using the experimental results of a 49-level single-phase inverter.

Symmetric multilevel inverter with reduced components based on non-insulated dc voltage sources

Abstract: Multilevel inverters have an important portion in power processing in power systems. These inverters have some inherent advantages such as ability to operate with high power and voltage, improved output waveform quality and flexibility which make them attractive and more popular. This study proposes a new topology based on the non-insulated dc voltage sources for multilevel inverter with reduced number of switching devices. As a result, it reduces control complexity and gate driver circuits. The proposed topology is a general topology which can be easily extended to a desired number of voltage levels. All of the desired output voltage levels (both odd and even) can be achieved using the proposed topology. The validity of the proposed multilevel inverter is verified with both computer simulation and experimental results from a 15-level laboratory prototype.

Developed embedded switched-Z-source inverter

Abstract: In this study, a new topology for switched Z-source inverter is proposed. This inverter in comparison with the conventional Z-source inverter needs higher number of active elements, lower number of capacitors and inductors. Reduction of weight, size and cost are the main advantages of the proposed topology. In addition, this inverter is able to solve the problem of short circuit across the inverter leg and consists of higher value of voltage gain when compared with the conventional switched boost inverter. Moreover, the developed topology of the proposed inverter based on switched-inductor cells is introduced. The performance of the proposed inverter in different operating modes is investigated. The proposed topologies are also compared with the conventional Z-source inverters from different points of view such as number of elements, the voltage gain and capability of tolerate the inverter short circuit. Finally, the accuracy performance of the proposed inverter is reconfirmed by using the simulation results in EMTDC/PSCAD software and also experimental results.

Multi-level conversion : high voltage choppers and voltage-source inverters

Abstract: The authors discuss high-voltage power conversion. Conventional series connection and three-level voltage source inverter techniques are reviewed and compared. A novel versatile multilevel commutation cell is introduced: it is shown that this topology is safer and more simple to control, and delivers purer output waveforms. The authors show how this technique can be applied to either choppers or voltage-source inverters and generalized to any number of switches.<>

Modular Multilevel Converters for HVDC Applications: Review on Converter Cells and Functionalities

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.

A Single-Phase Cascaded Multilevel Inverter Based on a New Basic Unit With Reduced Number of Power Switches

Abstract: In this paper, a new single-phase cascaded multilevel inverter is proposed. This inverter is comprised of a series connection of the proposed basic unit and is able to only generate positive levels at the output. Therefore, an H-bridge is added to the proposed inverter. This inverter is called the developed cascaded multilevel inverter. In order to generate all voltage levels (even and odd) at the output, four different algorithms are proposed to determine the magnitude of dc voltage sources. Reduction in the number of power switches, driver circuits, and dc voltage sources is the advantage of the developed single-phase cascaded multilevel inverter. As a result, the installation space and cost of the inverter are reduced. These features are obtained by the comparison of the conventional cascaded multilevel inverters with the proposed cascaded topology. The ability of the proposed inverter to generate all voltage levels (even and odd) is reconfirmed by using the experimental results of a 15-level inverter.

A New General Topology for Cascaded Multilevel Inverters With Reduced Number of Components Based on Developed H-Bridge

Abstract: In this paper, a new general cascaded multilevel inverter using developed H-bridges is proposed. The proposed topology requires a lesser number of dc voltage sources and power switches and consists of lower blocking voltage on switches, which results in decreased complexity and total cost of the inverter. These abilities obtained within comparing the proposed topology with the conventional topologies from aforementioned points of view. Moreover, a new algorithm to determine the magnitude of dc voltage sources is proposed. The performance and functional accuracy of the proposed topology using the new algorithm in generating all voltage levels for a 31-level inverter are confirmed by simulation and experimental results.

A General Review of Multilevel Inverters Based on Main Submodules: Structural Point of View

Abstract: Multilevel inverters (MLIs) are being used in wide range of power electronic applications. These converters have attracted a lot of attention during recent years and exist in different topologies with similar basic concepts. This paper presents five main submodules (SMs) to be used as the basic structures of MLIs. The paper reviews the common MLI topologies from the structural point of view. The topologies are divided into the different SMs to show conventional MLI configurations and future topologies that can be created from the main SMs. A comparative study between different topologies is performed in detail. The MLIs are categorized and investigated with from different perspectives such as the number of components, the ability to create inherent negative voltage, working in regeneration mode and using single dc source.