The cascaded multilevel inverters are suitable topologies when a high number of voltage levels is needed. Nonetheless, cascaded topologies possess the main drawback of a high number of power switches and gate drivers that make sophisticated control, reducing efficiency, and increasing cost. This paper proposes a new fundamental switched-diode topology which capable of generating five positive voltage levels with only three power switches, three power diodes, and three dc voltage sources. Based on a combination of the n number of new fundamental topology two cascaded topologies are proposed which increase the number of voltage levels and decrease the number of power switches and voltage stress. The proposed cascaded topologies can operate in asymmetric dc sources so different dc voltage source magnitudes are submitted to minimize the number of components. The main advantages of the proposed cascaded topologies are reducing the number of power switches and gate drivers with reasonable dc voltage sources count in comparison with other state-of-the-art cascaded topologies. Furthermore, the proposed topologies reduce the cost in comparison with other recently multilevel inverter topologies. The power loss analysis and the recommended application for the proposed topologies are discussed. The simulation and experimental works are presented to verify the operation correctness of the proposed topologies.Index Terms-Single-phase multilevel power converter, cascaded configurations, symmetrical and asymmetrical.
This article proposes two generalized multilevel inverter configurations that reduce the number of switching devices, isolated DC sources, and total standing voltage on power switches, making them suitable for renewable energy sources. The main topology is a multilevel inverter that handles two isolated DC sources by ten power switches to create twenty-five voltage levels. Based on the proposed main topology two generalized multilevel inverters are introduced to indicate flexibility in designing and also to minimize the number of elements. The optimal topologies for both extensive multilevel inverters are derived from different design objectives such as minimizing the number of elements (gate drivers, DC sources), achieving a large number of levels, and minimizing the total standing voltage. The main advantages of proposed topologies are a reduced number of elements than other multilevel inverters based on the comparison studies which is performed among the proposed topologies and other topologies. The power loss analysis and standalone PV application of the proposed topologies are discussed. The experimental results are presented for the proposed topology to demonstrate the correct operation of the proposal.INDEX TERMS single-phase multilevel inverters; generalized topologies; cascaded multilevel inverters; symmetric and asymmetric operations, renewable energy sources, photovoltaic system.
This article presents a sub-module topology for switched DC source cascaded multilevel inverter configurations that require fewer switching devices and can generate a high number of voltage levels which is suitable for renewable energy sources. The proposed sub-module topology comprises eight semiconductor switches and four DC voltage sources that generate fifteen voltage levels. Furthermore, the cascaded topology is presented to increase the output voltage levels and to minimize the number of components. The proposed sub-module inverter and its cascaded topology are compared with several multilevel inverters to indicate the advantages and drawbacks of the proposal. The comparison studies show the proposed topologies require a lower number of switching devices and gate drivers in competition with other multilevel inverter topologies. Besides, the proposed cascaded topology reduces the cost of the inverter in comparison to other multilevel inverter configurations. Furthermore, the power loss calculations and the implementation of the proposed topology in photovoltaic applications are discussed. Finally, the performance of the proposal is verified by simulation and experimental results for both symmetric and asymmetric sub-module topologies as well as for the proposed cascaded topology.INDEX TERMS DC-AC power converters; multilevel inverters, grid-connected PV inverters, photovoltaic systems, renewable energy sources.
Asymmetric multilevel inverters generate high-quality output voltage using the same number of components as symmetric multilevel inverters. The main drawback of these topologies is that they require a large number of DC voltage sources, and the power switches have to endure high voltage stress. In this paper, a sub-module inverter topology is proposed to reduce the number of DC voltage sources and voltage stress on the switches of asymmetric multilevel inverters. The proposed sub-module inverter is able to generate fifteen voltage levels by using two DC power supplies and a capacitor. The voltage of the capacitor can be automatically charged at half of the input DC power supply without the need for any sensors. In addition, the capacitor charging operation does not produce any inrush current because it is charged by the direction of the output current, so it has an advantage over switch capacitor multilevel inverters. A modular topology is also presented based on the proposed sub-module inverter to achieve high voltage levels while reducing the number of elements. A comprehensive comparison between the proposal and other multilevel inverter topologies is performed to approve the proposed inverter design. In addition, thermal and loss distribution simulation of the proposed sub-module inverter is performed. Finally, the performance, efficiency, and accuracy of the proposed inverter are confirmed through laboratory prototyping.INDEX TERMS DC-AC power converters; multilevel inverter, switched capacitor circuit.
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