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.<<ETX>>

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

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.

A Novel Multilevel Inverter Based on Switched DC Sources

In this paper, a dc to ac converter with the ability of voltage increasing is presented. This inverter is designed in a way that just one dc source is used. Also, by using power storage technique and with combining charged capacitors and dc source in series form, output voltage levels can be increased. This inverter is in a modular structure and has the ability of capacitor's voltage self-balancing. H-bridge inverter was not used at the end of the proposed converter and all elements tolerate a voltage stress equal to the amount of input dc source. This leads to remarkable decrease of total standing voltage and peak inverse voltage. Other advantage of the proposed inverter is its potentiality of performance in high-frequency applications. The modular form of the proposed inverter provides the potentiality of extension to higher voltage levels and eases the maintenance. Moreover, considering to the fact that the stress of all components of the suggested inverter is equal to the input source, the performance in high voltage is added to the characteristics of the proposed inverter. The nine-level structure of the proposed inverter is simulated and laboratory test is carried out for the verification of its performance.

A Self-Balanced Step-Up Multilevel Inverter Based on Switched-Capacitor Structure

In this paper, a novel platform for the single phase switched-capacitor multilevel inverters (SCMLIs) is presented. It has several advantages over the classical topologies, such as an appropriate boosting property, higher efficiency, lower number of required dc voltage sources, and other accompanying components with less complexity and lower cost. The basic structure of the proposed converter is capable of making nine-level of the output voltage under different kinds of loading conditions. Hereby, by using the same two capacitors paralleled to a single dc source, a switched-capacitor (SC) cell is made that contributes to boosting the value of the input voltage. In this case, the balanced voltage of the capacitors can be precisely provided on the basis of the series–parallel technique and the redundant switching states. Afterward, to reach the higher number of output voltage levels, two suggested SC cells are connected to each other with a new extended configuration. Therefore, by the use of a reasonable number of required power electronic devices, and also by utilizing only two isolated dc voltage sources, which their magnitudes can be designed based on either symmetric or asymmetric types, a 17- and 49-level of the output voltage are obtained. Based on the proposed extended configuration, a new generalized version of SCMLIs is also derived. To confirm the precise performance of the proposed topologies, apart from the theoretical analysis and a complete comparison, several simulation and experimental results are also given.

A New Boost Switched-Capacitor Multilevel Converter With Reduced Circuit Devices

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.

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

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.

Multilevel Inverter Topologies With Reduced Device Count: A Review

This study introduces a new multilevel converter topology, which can synthesise all possible additive and subtractive combinations of input DC levels in the output voltage waveform with fewer power electronic switches. An appropriate modulation scheme has also been proposed for low switching frequency operation of the proposed topology. As compared with the classic multilevel topologies, the proposed topology results in reduction of the number of switches and conduction losses. The operation and performance of the proposed multilevel converter has been ascertained through simulations and verified experimentally for single-phase nine-level multilevel inverter. Moreover, a 15-level inverter with asymmetric source configuration has been also investigated for charge balance control using the proposed modulation scheme. The same has been verified experimentally for effective balanced power delivery.

Topology for multilevel inverters to attain maximum number of levels from given DC sources

As multilevel inverters are gaining increasing importance, newer topologies are being proposed to reduce part count for large number of levels in output voltage. A simplified five-level inverter has been recently reported in the literature to reduce component count. The topology comprises of floating input DC sources connected in opposite polarities through power switches. The structure requires lesser active switches as compared with conventional cascaded H-bridge topology with much reduced switching losses. Available literature present generalisation of the topology with symmetrical sources, but no investigations are made for equal load sharing and asymmetrical configurations. This study presents a comprehensive analysis of the aforementioned topology, referred to as cross-connected sources-based multilevel inverter (CCS-MLI). The topology is analysed for both symmetric and asymmetric source configurations. Also, a new algorithm for asymmetric source configuration suitable for CCS-MLI is proposed. A control scheme is also proposed for equal load sharing in five-level topology. Investigations are made for possibility of equal load sharing in higher level structures and fundamental frequency switching of switches bearing higher voltage stresses. Various concepts are verified with simulations and experimental studies.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-pel.2012.0438

Comprehensive review of a recently proposed multilevel inverter

A new topology for multilevel DC–AC conversion is presented in this study. It consists of isolated symmetric input DC sources alternately connected in opposite polarities through power switches. The structure allows synthesis of multilevel waveform using reduced number of power switches as compared to the classical topologies. The working principle of the proposed topology is explained with the help of a single-phase five-level inverter. Simulation studies are carried out in MATLAB/Simulink environment and experimental validations are obtained on a laboratory prototype. An exhaustive comparison of the proposed topology against the classical cascaded H-bridge topology indicates reduction in number of power switches, losses, installation area and converter cost.

Krishna Kumar Gupta

Papers

Multilevel Inverter Topologies With Reduced Device Count: A Review

A Novel Multilevel Inverter Based on Switched DC Sources

Topology for multilevel inverters to attain maximum number of levels from given DC sources

Comprehensive review of a recently proposed multilevel inverter

Multilevel inverter topology based on series connected switched sources