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

This paper introduces a novel integrated series power pulsation buffer (iSPPB) concept for a single-phase AC-to-DC two-switch buck+boost PFC rectifier to compensate the fluctuating power mismatch between the AC input and the DC output. Accordingly the DC-link capacitance can be drastically reduced and an electrolytic-capacitor-Iess PFC rectifier system featuring a higher power density and an increased lifetime is obtained. The proposed iSPPB concept consists of a simple full-bridge circuit with a buffer capacitor and is placed in series with the buck-boost inductor thus no additional inductive component is required for the iSPPB realization. The basic operating principle of the buck+boost PFC rectifier with iSPPB is investigated and the characteristic waveforms are presented. As shown in the analysis due to the employment of the iSPPB also the maximum buck+boost inductor current is reduced which compared to the conventional rectifier system without iSPPB allows to further downsize the inductive component. Consequently the major drawbacks of conventional single-phase PFC rectifiers are eliminated. Furthermore the control structure is presented and the proper operation is verified based on a closed-loop circuit simulation. Finally the proposed buck+boost PFC rectifier with iSPPB and a conventional two-switch implementation employing electrolytic capacitors are quantitatively compared by means of simple performance indices.

Novel Single-Phase Buck+Boost PFC Rectifier with Integrated Series Power Pulsation Buffer

GOOGLE / IEEE Little-Box Challenge

This paper analyzes challenges that arise when the rotational speed in magnetically levitated hollow-shaft PMSMs is increased. Going to higher speeds highlights the advantages of such machines as being contact and contamination free, but leads to considerably higher losses. We propose a model and supply experimental data and simulations to subdivide losses into different categories with regard to specific optimizations. We particularly focus on the high rotor shell eddy current losses specific for this machine.

Analysis of rotor shell losses in a magnetically levitated homopolar hollow-shaft permanent magnet synchronous motor

This paper presents a novel closed loop current control strategy for a hybrid 12-pulse rectifier that uses a two-switch boost stage for output voltage regulation. Unlike previous attempts to mitigate input current distortion, e.g. by injecting voltages on the rectifier output side in open loop control mode, this new closed loop current control scheme directly controls the input current space vector and/or impresses sinusoidal input currents. In this paper, the control strategy is explained and the modulation functions for each pi/3-wide mains voltage sector are derived. The hardware implementation is described, and experimental results demonstrate that the control strategy ensures a high quality input current for ideal or distorted mains.

https://www.hpe.ee.ethz.ch/uploads/tx_ethpublications/04592136.pdf

Johann W. Kolar

Papers

Novel Single-Phase Buck+Boost PFC Rectifier with Integrated Series Power Pulsation Buffer

GOOGLE / IEEE Little-Box Challenge

Analysis of rotor shell losses in a magnetically levitated homopolar hollow-shaft permanent magnet synchronous motor

Closed loop input current control of a hybrid 12-pulse rectifier

Google Little-Box Reloaded