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

A switching device for switching a current between a first terminal (1) and a second terminal (2) comprises a cascode circuit having a series connection of a first semiconductor switch (M) and a second semiconductor switch (J), wherein the two semiconductor switches (M, J) are connected to each other by a common point (13), and the first semiconductor switch (M) is controlled by way of a first control input in accordance with a voltage between the first control input and the first terminal (1), and the second semiconductor switch (J) is controlled by way of a second control input (4) in accordance with a voltage between the second control input (4) and the common point (13). To this end, a control circuit having a specifiable capacitance (C) is connected between the second terminal (2) and at least one of the control input.

Switching device having a cascode circuit

Fundamentals and Application-Oriented Evaluation of Solid-State Transformer Concepts

This paper compares two bearingless slice motor topologies, namely the temple and slotless designs, with respect to the achievable motor efficiency for pump applications. Stator losses, passive stiffness properties and the achievable torque are determined by means of 3D FEM simulations. Some basic pump design guidelines are introduced and the expected motor performance is evaluated for typical operating conditions encountered in medical applications. It is shown that the temple design outperforms the slotless design in all but low pressure applications. Two prototypes, one radial and one axial pump, are manufactured by means of stereolitograpy 3D printing. The hydraulic characteristics of the designs are measured using the temple and slotless motor for the radial and the axial pump, respectively. The radial pump exhibits significantly higher pressure-numbers, while the axial design yields higher flow-numbers.

Comparison of Bearingless Slice Motor Topologies for Pump Applications

Integrated Voltage Regulators (IVRs) have become a viable solution for microprocessor's power delivery. The active parts of the most recent IVRs are built in deep-submicron CMOS technologies and use stacked transistors to allow for the use of advanced low voltage devices with superior switching performance compared to the higher voltage long-channel devices. This paper evaluates three different topologies of CMOS half-bridge converters with respect to efficiency, implementation effort, suitability for on-chip integration, and multiphase applications: the conventional half-bridge converter, the half-bridge converter with conventional Active Neutral Point Clamping (ANPC), and a halfbridge converter with a modified circuit to achieve ANPC. In-depth analysis of the transient processes during switching for all three converters, based on Cadence simulations, reveal that both half-bridge converters with ANPC achieve proper balancing of the blocking voltages of the main transistors and are capable to attain similar efficiencies of 93% at an output power of 200 mW, input and output voltages of 1.6 V and 0.8 V, respectively, and a switching frequency of 150 MHz, which is 1% higher than the one attained with the conventional half-bridge converter. Of the two ANPC half-bridge converters, however, the proposed topology allows to completely turn off its entire power stage or parts of it, features less efficiency sensitivity to variations of dead-time, and achieves the peak efficiency at relatively higher dead-time values. These qualities render the proposed topology particularly suitable for multiphase systems and low load operation.

Analysis and comparative evaluation of stacked-transistor half-bridge topologies implemented with 14 nm bulk CMOS technology

In this paper the current stress on the power components a direct three-phase boost-type unity power factor rectifier is analyzed in order to provide a basis for a system design under restriction of the height to 2-U. The conduction losses of the power semiconductors are calculated using analytical approximations of the average and rms values of the component currents; the switching losses are taken from previous experimental investigations. Based on this data an overview of the estimated power losses is given for the rectifier system for 10.5kW/800VDC output and 320V/400V/480V/530V (rms, line-to-line) mains voltage and the corresponding efficiency figures are calculated. Finally, topics of the continuation of the research are identified as, e.g., the realization of a prototype in order to verify the theoretical results experimentally also for unbalanced mains voltage conditions and with non-ideal components such as nonlinear input inductors employing iron powder cores.

/pdf/a-novel-10kw-2-u-three-phase-unity-power-factor-rectifier-2ny9n4houb.pdf

Johann W. Kolar

Papers

Switching device having a cascode circuit

Fundamentals and Application-Oriented Evaluation of Solid-State Transformer Concepts

Comparison of Bearingless Slice Motor Topologies for Pump Applications

Analysis and comparative evaluation of stacked-transistor half-bridge topologies implemented with 14 nm bulk CMOS technology

A Novel 10kW 2-U Three-Phase Unity Power Factor Rectifier Module