Special Issue "Multi-Level Converters"

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A special issue of Electronics (ISSN 2079-9292).

Deadline for manuscript submissions: closed (30 April 2015)

Special Issue Editor

Guest Editor
Prof. Dr. Bimal K. Bose (Website)

Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, TN 37996-2100, USA
Phone: 865-974-8398
Interests: power electronics; renewable energy systems; electric motor drives; fuzzy logic and neural network applications; electric and hybrid vehicles

Special Issue Information

Dear Colleagues,

Multi-level voltage source converters are characterized by having more than two voltage levels at the output compared to traditional converters which have two voltage levels. This class of converters is used in high voltage, high power (multi-MWs) applications, replacing the classical thyristor-based cycloconverters, load-commutated inverters (LCI) and current-fed converters. Such applications include induction and synchronous motor drives for various industrial applications, high voltage dc (HVDC) systems, flexible ac transmission systems (FACTS), static VAR compensators (SVC), active filters (AF), photovoltaic and wind generation systems, etc. The standard topologies of these converters are diode-clamped neutral-point clamped converter (NPC), flying capacitor (FC) converter and modular multi-level converters (MMC). The MMCs are again sub-classified into cascaded H-bridge (CHB) and cascaded half-bridge topologies. The general advantages of multi-level converters are the easy static and dynamic voltage sharing of the devices (IGBT or IGCT), improved PWM quality, reduced dv/dt and di/dt and improved reliability, compared to the two-level high voltage converters with a large number of devices in series. The MMC has the additional advantages of inherent low device voltage rating and a fault-tolerant capability. Considering their importance, multi-level converters are undergoing intense technological developments as revealed in recent literature relating to advanced topology development, modulation algorithms, control strategies, fault diagnostics and fault-tolerant controls. With the advent of large bandgap (SiC and GaN) power semiconductor devices with high voltage and high power, multi-level converters for industrial applications will be easily extended to a much higher range of power.

Prof. Dr. Bimal K. Bose
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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Keywords

  • high power applications
  • high voltage dc (HVDC) transmission
  • flexible ac transmission system (FACTS)
  • industrial ac drives
  • photovoltaic system
  • wind generation system
  • fault-tolerant control of converter
  • large bandgap devices

Published Papers (6 papers)

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Editorial

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Open AccessEditorial Multi-Level Converters
Electronics 2015, 4(3), 582-585; doi:10.3390/electronics4030582
Received: 24 August 2015 / Accepted: 6 September 2015 / Published: 9 September 2015
PDF Full-text (145 KB) | HTML Full-text | XML Full-text
Abstract In the history of modern power electronics evolution, we are now going through the era of multi-level converters [1]. [...] Full article
(This article belongs to the Special Issue Multi-Level Converters)

Research

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Open AccessArticle Use of Three-Level Power Converters in Wind-Driven Permanent-Magnet Synchronous Generators with Unbalanced Loads
Electronics 2015, 4(2), 339-358; doi:10.3390/electronics4020339
Received: 25 April 2015 / Accepted: 9 June 2015 / Published: 15 June 2015
Cited by 1 | PDF Full-text (3070 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes the design and implementation of three-level power converters for wind-driven permanent-magnet synchronous generators with unbalanced loads. To increase voltage stress and reduce current harmonics in the electrical power generated by a wind generator, a three-phase, three-level rectifier is used. [...] Read more.
This paper describes the design and implementation of three-level power converters for wind-driven permanent-magnet synchronous generators with unbalanced loads. To increase voltage stress and reduce current harmonics in the electrical power generated by a wind generator, a three-phase, three-level rectifier is used. Because a synchronous rotating frame is used on the AC-input side, the use of a neutral-point-clamped controller is proposed to increase the power factor to unity and reduce current harmonics. Furthermore, a novel six-leg inverter is proposed for transferring energy from the DC voltage to a three-phase, four-wire AC source with a constant voltage and a constant frequency. The power converters also contain output transformers and filters for power buffering and filtering, respectively. All three output phase voltages are fed back to control the inverter output during load variations. A digital signal processor is used as the core control device for implementing a 1.5 kV, 75 kW drive system. Experimental data show that the power factor is successfully increased to unity and the total current harmonic distortion is 3.2% on the AC-input side. The entire system can attain an efficiency of 91%, and the voltage error between the upper and lower capacitors is approximately zero. Experimental results that confirm the high performance of the proposed system are presented. Full article
(This article belongs to the Special Issue Multi-Level Converters)
Open AccessArticle An Improved Asymmetric Cascaded Multilevel D–STATCOM with Enhanced Hybrid Modulation
Electronics 2015, 4(2), 311-328; doi:10.3390/electronics4020311
Received: 30 December 2014 / Revised: 15 May 2015 / Accepted: 27 May 2015 / Published: 3 June 2015
Cited by 1 | PDF Full-text (1305 KB) | HTML Full-text | XML Full-text
Abstract
Problems related to power quality, which in the last years were responsible only for small losses in low-voltage distribution systems, are now causing damage to power apparatuses and financial losses also in medium-voltage systems. The necessity of a better quality of power [...] Read more.
Problems related to power quality, which in the last years were responsible only for small losses in low-voltage distribution systems, are now causing damage to power apparatuses and financial losses also in medium-voltage systems. The necessity of a better quality of power supply encourages the development of new specific custom power devices directly connected in medium-voltage distribution systems. It is well know that the multilevel converters are capable of being installed directly in the medium voltage, and presents several advantages when compared with conventional two-level converters. Some topologies, like the asymmetric cascaded multilevel converter, presents difficulties in regulating the voltages of all isolated dc-link capacitors. In this context, this article presents an asymmetric nineteen-level D–STATCOM (Distribution Static Synchronous Compensator) with a reactive power and dc-link regulation control loops for generic cascaded multilevel converters in order to improve the power quality in medium-voltage distribution systems. The performance of the proposed control method for a multilevel D–STATCOM is presented and evaluated in a downscaled prototype. Full article
(This article belongs to the Special Issue Multi-Level Converters)
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Open AccessArticle A Flexible Power Electronics Configuration for Coupling Renewable Energy Sources
Electronics 2015, 4(2), 283-302; doi:10.3390/electronics4020283
Received: 23 March 2015 / Revised: 2 May 2015 / Accepted: 4 May 2015 / Published: 11 May 2015
Cited by 1 | PDF Full-text (1828 KB) | HTML Full-text | XML Full-text
Abstract
A combination of series, parallel and multilevel power electronics has been investigated as a potential interface for two different types of renewable energy sources and in order to reach higher power levels. Renewable energy sources are typically dispersed in a territory, and [...] Read more.
A combination of series, parallel and multilevel power electronics has been investigated as a potential interface for two different types of renewable energy sources and in order to reach higher power levels. Renewable energy sources are typically dispersed in a territory, and sources, like wind and solar, allow small to medium-scale generation of electricity. The configuration investigated in this article aims at adapting the coupling solution to the specific generation characteristics of the renewable energy source to make it fit the electrical network. The configuration consists of a combination of three-phase multilevel converters and single-phase inverters, which are designed to provide flexibility, high power quality and high efficiency. A detailed analysis and simulation is performed to identify the properties in conjunction with the electrical grid requirements and the potential challenges encountered during operation. An optimized operation example of wind generation combined with solar PV generation is presented to exemplify the flexibility and benefits of the proposed configuration. Full article
(This article belongs to the Special Issue Multi-Level Converters)
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Open AccessArticle Analysis of a Multilevel Dual Active Bridge (ML-DAB) DC-DC Converter Using Symmetric Modulation
Electronics 2015, 4(2), 239-260; doi:10.3390/electronics4020239
Received: 30 January 2015 / Accepted: 2 April 2015 / Published: 20 April 2015
Cited by 2 | PDF Full-text (1200 KB) | HTML Full-text | XML Full-text
Abstract
Dual active bridge (DAB) converters have been popular in high voltage, low and medium power DC-DC applications, as well as an intermediate high frequency link in solid state transformers. In this paper, a multilevel DAB (ML-DAB) has been proposed in which two [...] Read more.
Dual active bridge (DAB) converters have been popular in high voltage, low and medium power DC-DC applications, as well as an intermediate high frequency link in solid state transformers. In this paper, a multilevel DAB (ML-DAB) has been proposed in which two active bridges produce two-level (2L)-5L, 5L-2L and 3L-5L voltage waveforms across the high frequency transformer. The proposed ML-DAB has the advantage of being used in high step-up/down converters, which deal with higher voltages, as compared to conventional two-level DABs. A three-level neutral point diode clamped (NPC) topology has been used in the high voltage bridge, which enables the semiconductor switches to be operated within a higher voltage range without the need for cascaded bridges or multiple two-level DAB converters. A symmetric modulation scheme, based on the least number of angular parameters rather than the duty-ratio, has been proposed for a different combination of bridge voltages. This ML-DAB is also suitable for maximum power point tracking (MPPT) control in photovoltaic applications. Steady-state analysis of the converter with symmetric phase-shift modulation is presented and verified using simulation and hardware experiments. Full article
(This article belongs to the Special Issue Multi-Level Converters)
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Other

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Open AccessConcept Paper Redundancy Determination of HVDC MMC Modules
Electronics 2015, 4(3), 526-537; doi:10.3390/electronics4030526
Received: 30 April 2015 / Revised: 16 July 2015 / Accepted: 29 July 2015 / Published: 4 August 2015
Cited by 2 | PDF Full-text (383 KB) | HTML Full-text | XML Full-text
Abstract
An availability and a reliability prediction has been made for a high-voltage direct-current (HVDC) module of VSC (Voltage Source Converter) containing DC/DC converter, gate driver, capacitor and insulated gate bipolar transistors (IGBT). This prediction was made using published failure rates for the [...] Read more.
An availability and a reliability prediction has been made for a high-voltage direct-current (HVDC) module of VSC (Voltage Source Converter) containing DC/DC converter, gate driver, capacitor and insulated gate bipolar transistors (IGBT). This prediction was made using published failure rates for the electronic equipment. The purpose of this prediction is to determinate the additional module redundancy of VSC and the used method is “binomial failure method”. Full article
(This article belongs to the Special Issue Multi-Level Converters)

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