Multilevel converters have been under research and development for more than three decades and have found successful industrial application. However, this is still a technology under development, and many new contributions and new commercial topologies have been reported in the last few years. The aim of this paper is to group and review these recent contributions, in order to establish the current state of the art and trends of the technology, to provide readers with a comprehensive and insightful review of where multilevel converter technology stands and is heading. This paper first presents a brief overview of well-established multilevel converters strongly oriented to their current state in industrial applications to then center the discussion on the new converters that have made their way into the industry. In addition, new promising topologies are discussed. Recent advances made in modulation and control of multilevel converters are also addressed. A great part of this paper is devoted to show nontraditional applications powered by multilevel converters and how multilevel converters are becoming an enabling technology in many industrial sectors. Finally, some future trends and challenges in the further development of this technology are discussed to motivate future contributions that address open problems and explore new possibilities.

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Recent Advances and Industrial Applications of Multilevel Converters

An Introduction to MultiAgent Systems.

Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

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A review of single-phase improved power quality AC-DC converters

Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

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Light-emitting diodes

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 shows that versatile stand-alone photovoltaic (PV) systems still demand on at least one battery inverter with improved characteristics of robustness and efficiency, which can be achieved using multilevel topologies. A compilation of the most common topologies of multilevel converters is presented, and it shows which ones are best suitable to implement inverters for stand-alone applications in the range of a few kilowatts. As an example, a prototype of 3 kVA was implemented, and peak efficiency of 96.0% was achieved.

Multilevel Inverter Topologies for Stand-Alone PV Systems

A maximum power point tracker for PV systems using a high performance boost converter

This paper deals with the analysis, design and optimization of a LCL filter topology to connect a 7MW NPC inverter to the grid. Following the requirements based on the IEEE 519-1992 recommendation and the German Guideline VDEW, simulation results were evaluated in order to access the performance of the proposed filter and the quality of the current injected into the grid.

LCL filter design for grid-connected NPC inverters in offshore wind turbines

This paper proposes the use of a three-phase high-frequency semicontrolled rectifier for wind energy conversion systems based on permanent magnet generators. The main advantages of the topology are: simplicity, since all active switches are connected to a common point, robustness, as short-circuit through a leg is not possible, and high efficiency due to reduced number of elements. As a disadvantage, higher but acceptable total harmonic distortion of the generator currents results. The complete operation of the converter and theoretical analysis are presented. Additionally, a single-phase pulsewidth modulation inverter is also employed in the grid connection. Experimental results on 5-kW prototype are presented and discussed.

A Three-Phase High-Frequency Semicontrolled Rectifier for PM WECS

This study presents the analysis, design and experimental evaluation of a high-voltage gain dc–dc converter applied to photovoltaic (PV) systems. A PV module rated at 17 V is connected to the input side, whereas the converter is responsible for stepping the voltage up to 311 V with the achievement of maximum power point tracking (MPPT). An experimental prototype rated at 100 W is implemented, which does not employ electrolytic capacitors, thus increasing the useful life of the arrangement and also allowing the incorporation of the converter to the PV module. Prominent advantages of the topology are low cost and simplicity in terms of the MPPT algorithm and the system implementation, which are mandatory characteristics for renewable energy applications.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-pel.2014.0520

Fernando L. M. Antunes

Papers

Multilevel Inverter Topologies for Stand-Alone PV Systems

A maximum power point tracker for PV systems using a high performance boost converter

LCL filter design for grid-connected NPC inverters in offshore wind turbines

A Three-Phase High-Frequency Semicontrolled Rectifier for PM WECS

High-voltage gain dc–dc boost converter with coupled inductors for photovoltaic systems