Johann W. Kolar

Bio: Johann W. Kolar is an academic researcher from ETH Zurich. The author has contributed to research in topics: Rectifier & Three-phase. The author has an hindex of 97, co-authored 965 publications receiving 36902 citations. Previous affiliations of Johann W. Kolar include Alstom & Infineon Technologies.

Modulation Scheme Optimization for a Dual Three-Phase Active Bridge (D3AB) PFC Rectifier Topology

Abstract: The recently presented Dual Three-Phase Active Bridge (D3AB) converter integrates a three-phase Power Factor Corrected (PFC) rectifier and a DC–DC converter stage with galvanic isolation, originating from the Dual Active Bridge converter, in a single converter unit, and accordingly features low complexity, high efficiency, and high power density. This paper proposes a multi-objective optimization procedure that considers the objectives of low RMS transformer currents and/or switching losses in order to identify Pareto-optimal low-loss modulation schemes for the D3AB rectifier that meet given specifications, prevent power pulsation, and facilitate interleaved operation. From the obtained results, which are verified by means of detailed circuit simulations, an improved modulation scheme is selected, which, compared to conventional modulation, reduces the primary-side switching losses by 54% and the total converter losses by 11%. Due to the general nature of the presented method, the application to other three-phase rectifier/inverter topologies is directly feasible.

Rotary electric machine and non-contact power generator

Abstract: Provided is a rotary electric machine including: a permanent magnet rotatable around a first rotational shaft and disposed at a distance from a main surface of a moving body rotating or moving, at least a part of a side surface of the permanent magnet continuous to an outer peripheral surface thereof being opposed to the main surface of the moving body, wherein the permanent magnet is rotated around the first rotational shaft by a reaction force acting on the permanent magnet, the reaction force being caused by eddy currents produced in the main surface of the moving body in such a direction as to hinder a change of magnetic flux from the permanent magnet, and a surface speed of the side surface of the permanent magnet opposed to the moving body is lower than a surface speed of the main surface of the moving body opposed thereto.

A multiphase ac power converter and method for controlling a multiphase ac power converter

Abstract: A power converter comprises • a multiphase primary stage between a multiphase voltage source and a DC link; • an input filter for the primary stage; • a secondary stage between the DC link and a multiphase load, with an additional bridge leg for a neutral point of the load; • the input filter comprising an input filter star point connected to a midpoint of the DC link via a connection capacitance (C my ); A method to control the converter comprises the steps for controlling a ground current ( i gnd ) flowing into the power converter: • an outer controller for the ground current ( i gnd ) by generating a reference value ( u * my ) for a voltage across the connection capacitance ( C my ); • an inner controller for this voltage ( u my ) generating a reference value ( i * zs ) for a zero sequence current flowing through the connection capacitance ( C my ); • a zero sequence current controller.

100MS/s 10-25MHz Wireless Voltage Probe

Abstract: For developing and testing of power electronic converters and circuits, voltages and currents have to be measured to verify the proper mode of operation. In cascaded converters or multi-level topologies, the voltages to be measured contain common mode components up to several kV with transients up to several tens of kV/µs. Conventional isolated voltage measurement systems do either not meet the high voltage isolation requirements or exhibit a rather large coupling capacitance to ground. In combination with the high voltage transients, this coupling capacitance on the one hand impacts the circuit under test and on the other hand influences the voltage measurement. To reduce these effects, the coupling capacitance of the measurement system must be minimized. In this paper, a wireless voltage probe (WVP) is introduced to measure accurately on a high and transient reference voltage with minimal impact on the circuit under test. The basic concept and practical realization of the WVP are discussed and finally verified with measurements on a high power medium voltage IGBT converter system.

Operating device for e.g. LED, of lighting system for lighting e.g. rooms, has power factor correction circuit comprising storage throttle that comprises secondary winding, where winding is switched in series with coupling capacitor

Abstract: The device (A) has a driver circuit for operating a lighting unit, and an energy storage for feeding the driver circuit A power factor correction circuit (PFC) is designed as a boost converter, where the circuit feeds the energy storage and comprises a storage throttle with a secondary winding The secondary winding is magnetically coupled with a primary coil of the storage throttle such that ripples of current is reduced or compensated by the storage throttle The secondary winding is switched in series with a coupling capacitor The power factor correction circuit is designed as a filter circuit and a rectifier circuit

I and i

Abstract: 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 …

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

Abstract: 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.

Recent Advances and Industrial Applications of Multilevel Converters

Abstract: 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.