Alfred Engler

Alfred Engler
Liebherr Elektronik GmbH, Germany · Development Technologies

Dr. Eng.

About

75
Publications
34,634
Reads
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1,940
Citations
Additional affiliations
January 2008 - August 2015
Liebherr-International Deutschland GmbH
Position
  • Manager

Publications

Publications (75)
Article
In the frame of the more electric aircraft and to achieve the goal of replacing hydraulic systems by electrical ones, the power density is one of the major key parameters for electrical designs. Recent advances in predevelopment activities and technologies allow today to be competitive in term of performances and weight with the existing solutions....
Conference Paper
This paper deals with the implementation of the opposition method for testing power electronics converter in aerospace applications. The methodology and test results are presented. The method is successfully applied on a 48kW inverter dedicated to future Electrical Environmental Conditioning System for aerospace application.
Conference Paper
A partial discharges-free power source is a prerequisite for appropriate partial discharges (PD) evaluation in power electronics systems. Moreover, the voltage waveform is a significant parameter which can affect the discharges’ nature. This paper describes the development of a PD-free voltage source delivering pulse width modulation voltage for re...
Conference Paper
This paper presents the impact of voltage fall time of SiC MOSFETs, applied in converters of aerospace DC fed AC drives, on a HF conducted EMI signals. Simple frequency domain behavioral model is proposed for the use. Simulation results and real system measurements are successfully compared. It was shown that appropriate tuning of MOSFET voltage fa...
Conference Paper
In order to achieve the goal of replacing hydraulic systems by electrical systems, the power density is a key parameter for electrical designs. Especially applications in unpressurized area require hermetic sealed heavily weighted housings. The approach to replace these housings by a sealed weight reduced open box design with liquid cooling covers...
Conference Paper
The implementation of power electronics in aircraft is progressively going up on the last aircraft developments. The aim is to replace current hydraulic, pneumatic or mechanical system by equivalent electrical systems. However, some major challenges need to be addressed: first of all, the power electronics systems must be lighter than the standard...
Chapter
This chapter describes intelligent control concepts for power electronics interfaced microsources. These controllers are responsible for voltage and frequency control in microgrids and are essential for stable microgrid operation. The chapter discusses control concepts based on frequency/active power and voltage/reactive power droops as applied on...
Conference Paper
This paper deals with the calculation of the common mode current at the input power supply of a driver board for power semiconductor modules. Applying a proven method for main power circuit to the driver stage, calculations are successfully compared with measurements and lead to an aerospace compliant filter design.
Conference Paper
Full-text available
The intentions of the More Electrical Aircraft (MEA) concept are weight reduction and higher efficiency by application of more electrical systems. Conventionally, power electronic devices apply 12-pulse autotransformers to rectify the 360 to 800 Hz supply. An interesting alternative is the parallel active power filter (APF), which compensates for t...
Conference Paper
Full-text available
Over the past years, the number of electrical systems in airplanes, and thus their power ratings have been rising. Therefore, the optimization of devices and actuators regarding efficiency and power density has become increasingly important. Besides the large topic of weight reduction at component level, aircraft manufacturers and several research...
Conference Paper
Full-text available
The rising number of electrical systems in airplanes and their power ratings, results in new grid architectures. A possible topology comprises several sub-networks with an active power filter maintaining the power quality at the connection point to the main bus. This paper presents the characterization and evaluation of 1700V SiC-MOSFET modules for...
Conference Paper
This paper deals with partial discharges issues in aerospace power electronic system. Indeed, considering the housing, due to the severe environment of the aerospace equipment, a standard solution is to provide a hermetically sealed product. This leads to reliability issue, weight and price increase. Not using a hermetically sealed housing is a pro...
Conference Paper
Full-text available
The requirements for high efficiency and low weight of subsystems in aerospace has led to increased research in power electronic devices. These play an important role in present and future airplanes. One major topic is the substitution of conventional hydraulic or pneumatic systems with electrical systems such as electrical environmental condition...
Article
This paper deals with the prediction of radiated emission of power electronics drive systems in the environmental conditions of aerospace applications. The aerospace norm and constraints define limits of radiated emissions for such systems. Thus, it is of importance to predict them in the design phase of the product development to ensure the electr...
Article
Full-text available
A major intention of the “More Electric Aircraft” concept (MEA) [1], is the use of power electronics instead of mechanical, hydraulical or pneumatical systems, which promises reduced weight, higher efficiency and less maintenance costs. This paper presents the design of rectifier topologies Active Power Factor Correction (APFC) and Autotransformer...
Conference Paper
Full-text available
This paper presents the power core developed for the 70kW inverter dedicated for future aeronautical applications in the frame of the MOET program, a FP6 European Integrated Project [1]. Description, principle of operation and experimental results are presented. Considered as a major sub-assembly of the inverter, attention has been paid on the desi...
Conference Paper
This paper presents the 70 kW inverter dedicated for future aeronautical applications in the frame of the MOET program, a FP6 European Integrated Project. Design considerations, principle of operation and experimental results will be presented hereunder. For DC to AC conversion, technologies improvements and specific integration allow reducing weig...
Article
This paper presents a transformerless three-phase inverter designed for the integration into a special type of a photovoltaic (PV) module, which is capable of providing an output voltage of several hundred volts. The chosen topology, a current-source inverter, features a single-stage power conversion system that directly feeds into the grid. The pr...
Article
Full-text available
Photovoltaic ac-modules may become a future trend in PV system technology. For a reliable integration of the power electronic converter into the PV panel (also called PV module) the thermal mission profile of the photo- voltaic system has to be analysed. In this paper, a mechatronic integration strategy is introduced and a thermal test setup is pre...
Article
Full-text available
Im Rahmen des europäischen Projekts PV-MIPS (Photovoltaic Module with Integra-ted Power Conversion and Interconnection System) werden Wechselrichter für die Integration in PV-Module unterschiedlicher Technologie entwickelt. Diese Kombination aus PV-Modul und Wechselrichter bildet ein AC-Modul. Es kann als geschlossenes System aufgefasst werden, das...
Conference Paper
Full-text available
This paper deals with the analysis, design and optimization of a LCL filter topology to connect a 7MW NPC inverter to the grid. Following the requirements based on the IEEE 519-1992 recommendation and the German Guideline VDEW, simulation results were evaluated in order to access the performance of the proposed filter and the quality of the current...
Conference Paper
Full-text available
Voltage control in networks with predominantly resistive coupling is most efficient when controlling the active power flow. By introducing a series connected inductor for a dedicated part of the network the coupling can be shifted to the inductive type. Hence the voltage in such sub-networks can be influenced by injection of reactive power. Further...
Conference Paper
Full-text available
A transformerless three-phase power conditioning unit interfacing with a high voltage (>200 V) photovoltaic module is presented. The chosen topology, a Current Source Inverter, features a single-stage power conversion system that feeds directly into the grid. A robust and highly efficient laboratory prototype of a Module Integrated Converter has be...
Conference Paper
Full-text available
Microgrids comprise Low Voltage distribution systems with distributed energy sources, such as micro-turbines, fuel cells, PVs, etc., together with storage devices, i.e. flywheels, energy capacitors and batteries, and controllable loads, offering considerable control capabilities over the network operation. These systems are interconnected to the Me...
Article
Full-text available
Das AC-Kopplungskonzept für Inselnetze hat sich in den letzten Jahren in vielen Systemen weltweit bewährt. Es zeichnet sich gegenüber herkömmlichen Konzepten durch eine Reihe von Vorteilen hinsichtlich der Anlagenplanung und des Aufbaus (Design, Installation, Erweiterbarkeit und Kompatibilität) aus und des senkt gleichzeitig die spezifischen System...
Article
Full-text available
In order to validate the different functions of a low voltage microgrid, a specific test configuration has been set up in the Design Centre for Modular Systems Technology ("DeMoTec") of the Institut für Solare Energieversorgungstechnik (ISET). In this highly innovative microgrid configuration, the grid control is distributed among three distant inv...
Conference Paper
Full-text available
This paper describes a micro grid management system developed using agent based technologies and its application to the effective management of generation and storage devices connected to a LV network forming a micro grid. The micro grid is defined as a set of generation, storage and load systems electrically connected and complemented by a communi...
Conference Paper
Full-text available
Within the frame of the European project "Microgrids" several test set-ups have been installed or enlarged at different laboratories. Three of them are presented in this contribution: a specially designed single phase system of the NTUA with agent control software, the DeMoTec at ISET, which is a general test site for DER and the flywheel test rig,...
Conference Paper
Full-text available
Remote electrification with island supply systems, the increasing acceptance of the microgrids concept and the penetration of the interconnected grid with DER and RES require the application of inverters and the development of new control algorithms. One promising approach is the implementation of conventional f/U-droops into the respective inverte...
Article
This contribution introduces two inverter topologies for fuel cell inverters. Furthermore the regulatory grid interface and the common control techniques are described. An outlook for the application of fuel cell inverters in microgrids with the respective control technique is presented.
Article
Full-text available
Remote electrification with island supply systems, the increasing acceptance of the microgrids concept and the penetration of the interconnected grid with distributed energy resources and renewable energy resources require the application of invert-ers and the development of new control algorithms. One promising approach is the implementation of co...
Article
Full-text available
Technological advances and environmental pressures are driving the interconnection of renewable energy sources to the distribution network. The interconnection of large amounts of non-traditional generation however causes problems in a network designed for 'conventional' operation. The use of power electronics interfaces and the 'bundling' of micro...
Conference Paper
Full-text available
The paper presents experimental results from the operation of a prototype microgrid system, installed in the National Technical University of Athens, which comprises a PV generator, battery energy storage, local load and a controlled interconnection to the LV grid. Both the battery unit and the PV generator are connected to the AC grid via fast-act...
Conference Paper
Full-text available
The consequent AC-coupling of generators, storage units and loads for setting up hybrid systems or hybrid microgrids is under investigation at ISET since more than ten years. After the development of suitable components like the PV-inverter Sunny Boy/sup /spl reg// and the battery inverter Sunny Island/sup /spl reg// and after the implementation of...
Article
Full-text available
In the majority of autonomous Aegean island grids, the annual penetration of wind energy is lower than 10%, even though there is exceptional wind potential in this area. This situation is due to large fluctuations of demand in summer and winter periods in combination with the technical restrictions of diesel gensets of the autonomous power stations...
Article
Full-text available
The integration of renewable energies into electrical power supply systems is of growing relevance. ISET has been working on this topic since more then ten years. The activities were starting with developing inverters for the integration of photovoltaic generators into the interconnected grid. After these activities emphasis was put on setting up i...
Article
Full-text available
Due to the increasing number of inverters in renewable supply systems and a lot of UPS-applications the control of single phase systems is becoming more important. Hence a new control strategy for single phase inverters has been derived which allows both precise control and fast signal conditioning. The vector control with PI-controllers, which is...
Article
Full-text available
The AC-coupling of components for stand-alone PV-battery-diesel hybrid power systems and the dis-tributed generation in renewable energy micro grids is a challenging task for the control technology. Today's systems mostly run in master/slave operation with one battery inverter or one genset as the grid master. Extendable distributed power supplies...
Article
Full-text available
The dynamic growth of grid-connected photovoltaic systems in some member countries of the Euro-pean Union has stimultated the development of high quality and reliable inverters as well as of other system compo-nents. By looking to the learning curves of these components it can be seen that cost reductions could be performed with the same speed as w...
Article
Full-text available
The approach of modular systems technology has now become generally accepted for the design of island grids with different renewable energy converters. This technology is characterised by a stipulated energy coupling (ac-bus bar 230/400 V, 50 Hz), a standardised information exchange and a supervisory control. These preconditions allow an adaptable...
Article
Full-text available
Die Bereitstellung elektrischer Energie kann nach den technischen Anforderungen in die Aufgaben • Einspeisung in leistungsstarke Netze, • Versorgung einzelner Lasten und • Bildung von Inselnetzen unterteilt werden. Während ein leistungsstarkes Netz die Netzgrößen vorgibt und zur Einspeisung die Netzanschlußbedingungen -im wesentlichen für Oberschwi...
Article
Full-text available
This paper deals with the basic design and benchmark of a multilevel dc-ac conversion system for interconnecting a high power wind turbine to the grid. The benchmark has been performed for different system voltages and devices in terms of efficiency, grid filter design and cost. In this context the NPC loss calculation and basic filter design rules...
Article
Full-text available
The test and validation of prototypes in the area of Distributed Generation is often related to the effect of these devices on the electrical grid. However, due to the scale of the mentioned equipment it is difficult to observe this effect when the device interacts with the main grid. A first approximation to this behavior can be simulated using a...
Article
The approach of modular systems technology has now become generally accepted for the design of island grids with different renewable energy converters. This technology is characterised by a stipulated energy coupling (ac-bus bar 230/400 V, 50 Hz), a standardised information exchange and a supervisory control. These preconditions allow an adaptable...
Article
Energy systems are experiencing an evolution from a completely centralized and rigid structure to a decentralized one. This change brings, however, a series of challenges as how to integrate and coordinate the increasing number of distributed generation resources (DG). One of the ways of integrating DG technologies is associating them in coordinate...
Article
Full-text available
Modular PV and hybrid systems are most suitable for local power supplies and can be easily adapted to the needs of the consumer. However, in order to overcome the problems of setting up expandable sup-ply systems based on multiple renewable energy sources, a standard communication interface has to be devel-oped. This paper puts forward the requirem...
Article
Full-text available
1 Werkzeuge und Vorgehensweise bei der Simulation Dem Entwickler stehen heute zahlreiche Werkzeuge für das Design elektronischer Schaltungen oder elektrischer Systeme zur Verfügung. Im einfachsten Fall ermöglichen solche Werkzeuge die Überprüfung eines vorhandenen Designs, aber auch Auslegung und Dimensionierung (z. B. von Reglern) werden unterstüt...
Article
Full-text available
Distributed Energy Resources (DER), e. g. wind turbines, combined heat and power units, photovoltaic and inverter controlled DER, gain importance in today's power system. Their fluctuating behaviour and their specific control characteristics require manifold investigations. Due to the nature of ATP-EMTP with regard to simulating supply structures i...
Article
Full-text available
Within the European project PV-MIPS (Photovoltaic Module with Integrated Power Conversion System) an inverter for the integration into a 240W high-voltage thin-film PV module in CIS (Copper Indium Diselenide) technology has been designed. This combination of PV module and inverter forms an AC module. At first, the paper provides an overview about p...
Article
This conference paper introduces parts of an ATP-EMTP model library, which was developed at ISET. The paper concentrates on two battery inverter models which are implemented in ATP-EMTP as well as in PowerFactory. Transient simula- tions in both tools show the response of the modelled battery inverter to load steps. The results of the simulations i...
Article
Full-text available
Within the project PV-MIPS (Photovoltaic Module with Integrated Power Conversion System) funded by the European Commission an inverter for a 200W PV module is being designed. In order to be successful the module integrated PV-MIPS inverter needs to meet strict requirements in terms of cost, reliability and compact-ness. The usage of thin film photo...
Article
Full-text available
Within the 6th framework program funded by the European Commission the project PV-MIPS (Photovoltaic Module with Integrated Power Conversion System) was launched in November 2004. Together with eleven European partners from Germany, Austria, Greece and the Netherlands a solar module with integrated in-verter shall be developed that can feed solar e...
Article
Full-text available
Renewable energies are gaining increasing importance for the electrical supply system. The integration of distributed electricity generation (DG) by many small generation units into the existing supply structure calls for new technological solutions. New developed devices, improved energy management procedures and advanced communication technologie...
Article
Full-text available
The AC-coupling of components for stand-alone PV-battery-diesel hybrid power systems and the distributed generation in renewable energy micro grids is a challenging task for the control technology. Today's systems mostly run in master/slave operation with one battery inverter or one genset as the grid master. Extendable distributed power supplies c...