There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Multilevel inverter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. This paper presents the most important topologies like diode-clamped inverter (neutral-point clamped), capacitor-clamped (flying capacitor), and cascaded multicell with separate DC sources. Emerging topologies like asymmetric hybrid cells and soft-switched multilevel inverters are also discussed. This paper also presents the most relevant control and modulation methods developed for this family of converters: multilevel sinusoidal pulsewidth modulation, multilevel selective harmonic elimination, and space-vector modulation. Special attention is dedicated to the latest and more relevant applications of these converters such as laminators, conveyor belts, and unified power-flow controllers. The need of an active front end at the input side for those inverters supplying regenerative loads is also discussed, and the circuit topology options are also presented. Finally, the peripherally developing areas such as high-voltage high-power devices and optical sensors and other opportunities for future development are addressed.

Multilevel inverters: a survey of topologies, controls, and applications

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.

/pdf/recent-advances-and-industrial-applications-of-multilevel-26fluutoc9.pdf

Recent Advances and Industrial Applications of Multilevel Converters

http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

Solid state modulators based on pulse transformer offer the advantage, that with the turns ratio of the transformer, the primary voltage ideally could be adapted to the available switch technology and a series connection of switches could be avoided. For increasing the power level several semiconductor switches must be connected in parallel and a balancing between the different switches must be guaranteed. There, the Matrix Transformer concept, which is based on multiple primary and/or secondary windings as well as on flux adding, offers superior performance with respect to the achievable rise times. However, the influence of the parasitic elements on the voltage and current distribution is quite involved. In this paper the influence of the parasitic elements of the Matrix Transformer on the current balancing and winding voltages is investigated based on reluctance models and the inherent current balancing of the Matrix Transformer for windings mounted on different cores is explained. Furthermore, the influence of parasitic load/transformer capacitances on the turn-off transient is discussed in detail.

https://www.hpe.ee.ethz.ch/uploads/tx_ethpublications/Transient.pdf

Transient behaviour of solid state modulators with Matrix Transformers

An increasing number of power electronic applications require high power density. Therefore, the switching frequency and switching speed have to be raised considerably. However, the very fast switching transients induce a strong voltage and current ringing. In this work, a novel damping concept is introduced where the parasitic wiring inductances are advantageously magnetically coupled with a damping layer for attenuating these unwanted oscillations. The proposed damping layer can be implemented using standard materials and printed circuit board manufacturing processes. The system behavior is analyzed in detail and design guidelines for a damping layer with optimized RC termination network are given. The effectiveness of the introduced layer is determined by layout parasitics which are calculated by application of the Partial Element Equivalent Circuit (PEEC) simulation method. Finally, simulations and measurements on a laboratory prototype demonstrate the good performance of the proposed damping approach.

Switching Transient Shaping by Application of a Magnetically Coupled PCB Damping Layer

Three-Phase PFC Rectifier and AC-AC Converter Systems - PART 1

Silicon carbide (SiC) switching devices have been widely discussed in power electronics due to their desirable properties and are believed to set new standards in efficiency, switching behavior, and power density for state-of-the-art converter systems. In this paper the design, construction, and performance of a 3 kVA All-SiC Current Source Converter (CSC) also known as Current DC-Link Back-to-Back Converter (CLBBC), is presented. CSC topologies have been successfully used for many years for high power applications. However, for low power range converter systems they could not compete with Voltage Source Converter (VSC) topologies with capacitors in the DC-link, since the link inductor has always been a physically large and heavy component due to the comparatively low switching frequencies of conventional high blocking voltage silicon devices. New SiC switches such as the JFET, which are providing simultaneously high voltage blocking, low switching losses, and low on-state resistance, offer new possibilities and allow for implementing a high switching frequency CLBBC and thus reducing size and weight of the DC-link inductor. The prototype CLBBC has been designed specifically for latest generation 1200 V, 6 A SiC JFETs for a target switching frequency of 200 kHz.

Johann W. Kolar

Papers

Transient behaviour of solid state modulators with Matrix Transformers

Switching Transient Shaping by Application of a Magnetically Coupled PCB Damping Layer

Three-Phase PFC Rectifier and AC-AC Converter Systems - PART 1

Design and Performance of a 200 kHz All-SiC JFET Current Source Converter

Bi-Directional Isolated DC-DC Converter for Next-Generation Power Distribution : Comparison of Converters Using Si and SiC Devices