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Alfred Rufer

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Related publications (215)

Control Challenges and Solutions for a Multi-cellular Converter for Use in Electricity Networks

This paper presents the concept of a multi-cellular power converter, structure targeted towards use in future electricity networks. Control of such a converter is challenging because of the distributed energy storage intrinsic to concept If the energy flow ...

2009

Investigations on a 1kVA Reactive Power Compensated Current Converter using monolithic RB-IGBT modules

Alfred Rufer, Daniel Siemaszko

This work presents a current converter topology with an added free-wheeling path on the output load. This converter allows the compensation of the reactive power consumption by forcing the input current fundamental component to be in phase with the input v ...

2009

Description and Efficiency Comparison of Two 25 kVA DC/AC Isolation Modules

Alfred Rufer, Frédéric Zurkinden, Daniel Siemaszko, Lukas Fleischli, Irma Villar

In the frame of the European project UNIFLEX-PM, two AC/AC converter topologies hove been studied and implemented. Both converters, rated for 25 kVA, are isolated by a medium-frequency power transformer. The first topology is based on a dual active bridge ...

2009

Global Loss Evaluation Methods for Nonsinusoidally Fed Medium-Frequency Power Transformers

Alfred Rufer, Irma Villar

Medium-voltage conversion systems, such as traction and grid-connected converters, are continuously evolving toward higher power densities. Consequently, volume, weight, and material reductions are becoming major design issues, which lead the research focu ...

2009

Poly-Phased Matrix Converter for large Synchronous Generators - Design of the Voltage Surge Protection

Alfred Rufer, Antoine Béguin

This paper introduces a special mx3 matrix converter connected between the stator of a poly-phased synchronous generator and a power grid. Some commutations of the chosen switching scheme induce voltage surges due to leakage inductances of the generator. T ...

Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2009

A Novel Multilevel Converter Structure Integrated into Power Systems and its Performance Evaluation

Alfred Rufer, Stephan Kenzelmann

The paper introduces an advanced multicellular power converter structure for flexible power management in future electricity networks. The power converter structure is analysed and the control approaches required in order to overcome the technical challeng ...

2009

Fuzzy Logic Control of the Cross Connected Intermediate Level (CCIL) Voltage Source Inverter

Alfred Rufer

The Cross Connected Intermediate Level (CCIL) Voltage Source Inverter Topology was first introduced in 2007 [1]. The idea behind this novel multilevel topology is to explore the area of reduced number of component topologies producing large number of volta ...

2009

Controlled Resonant Circuit with Commutated Capacitors using Self-Switching Power Devices

Alfred Rufer, Daniel Siemaszko, Christian Rod

This paper presents a preliminary work on a resonant circuit, also called AC-dipole. The resonance frequency of the circuit is changed by the mean of a variable capacitor connecting an inductor. For this purpose, a bank of switched capacitors of different ...

Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2009

Comparison of Control Strategies for Maximizing Energy in a Supercapacitor Storage Subsystem

Alfred Rufer, Philippe Barrade

A storage supercapacitor subsystem is studied for insertion in a series hybrid electric vehicle (Fig. 1). This subsystem is composed of a supercapacitor bank and a braking resistor used when the supercapacitor voltage is at its maximum value. Generally, wh ...

2009

The Monophasor Theory: Analytical Development and Practical Demonstration on a Single Phase Voltage Source Inverter

Alfred Rufer, Philippe Barrade, Yannick Louvrier, Stephan Kenzelmann

A method for simplifying the analytical treatment of single phase systems is introduced. This method, called monophasor theory, makes it possible to apply the same calculation methods and control strategies used for three-phase systems. This way, the spaci ...

Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2009

UNIFLEX-PM - A Key-Enabling Technology for Future European Electricity Networks

Alfred Rufer

More "green" power provided by Distributed Generation will enter into the European electricity network in the near future. hi order to control the powerflow and to ensure proper and secure operation of this future grid, with an increased level of the renew ...

2009

Multistage hydraulic gas compression/expansion systems and methods

Alfred Rufer

Multistage hydraulic systems and methods for converting the potential energy of a pressurized gas, particularly air, into mechanical work operating in motor, and for producing compressed gas from the mechanical work of the rotating shaft (A1.1 ) when rotat ...

2009

Vector Control of Single-Phase Voltage Source Converters based on Fictive Axis Emulation

Alfred Rufer, Stephan Kenzelmann, Behrooz Bahrani

This paper presents an alternative way for controlling the current of single-phase voltage source dc-ac inverters in a dq synchronous reference frame. In a dq reference frame, ac (time varying) quantities appear as dc (time invariant) quantities allowing t ...

Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2009

Altitude Performance of Heat sink in Standard Atmosphere

Alfred Rufer, Yannick Louvrier

Power Electronic components require cooling to limit junction temperatures to ensure long and reliable operation. Heat sinks are used for cooling the components. In applications which entail operation at altitudes, derating factors are provided by manufact ...

2009

Optimization of the Operating Point of a Vanadium Redox Flow Battery

Alfred Rufer, Christian Blanc

Modeling a vanadium redox flow battery (VRB) is intrinsically a multiphysics task based on electrochemistry and fluid mechanics. The electrochemical model predicts the stack voltage and determines the internal losses and the vanadium concentrations within ...

Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2009

Weight and efficiency optimization strategy of an interleaved DC-DC converter for a solar aircraft

Alfred Rufer, Philippe Barrade, Yannick Louvrier

Today, energy saving is one of the main objectives for engineers. In the case of mobile applications, energy can be saved by two different ways. First, decreasing the total masse of the system, and second, increasing the efficiency of the overall system.Th ...

Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2009

Transient Thermal Model of a Medium Frequency Power Transformer

Alfred Rufer, Irma Villar

Nowadays medium voltage conversion systems, like traction and energy distribution systems, aim to increase power density. Volume, weight and material reduction are gaining the market today. Due to the development of new high power semi-conductor devices a ...

2008

Rendements Energétiques de Convertisseurs DC-AC 25kVA Isolés à Deux ou Trois Etages

Alfred Rufer, Frédéric Zurkinden, Daniel Siemaszko, Lukas Fleischli

Dans le cadre du projet européen UNIFLEX-PM, deux topologies de convertisseur AC/AC ont été étudiées et implémentés. Les deux convertisseurs réalisés sont isolés par un étage transformateur moyenne fréquence pour une puissance nominale de 25kW. La première ...

2008

A New Three-Level Quadratic (T-LQ) DC-DC Converter Suitable for Fuel Cell Applications

Alfred Rufer

This paper presents a new non-insulated three-level DC-DC boost converter with quadratic static gain. ...

2008

Replacement and emulation of a lead-acid battery with supercapacitors for a UPS application

Alfred Rufer, Philippe Barrade, Yannick Louvrier

This contribution proposes the study of an ‘On-Line’ UPS, where adaptations have been made to replace the initial batteries with supercapacitors. As the electrical behavior of supercapacitors is different from that one of lead-acid batteries, a power elect ...

2008

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