Florian Grumm

Converter topology analysis for aircraft application

This paper deals with an aircraft weight optimization through an analysis of different load-converter-architectures. A major effort in the development of new aircraft is the reduction of the weight. This results from a direct relationship between aircraft mass and efficiency. At a first step the global onboard converter architecture is analyzed. In addition to the conventional architectures two DC-grid architectures are shown. In the second step a weight reduction through converter optimization is presented.

Influence of small Constant-Power-Loads on the power supply system of an aircraft

Today most electrical consumers in an aircraft grid are electronic loads. Compared to resistive or motoric loads these loads have constant power consumption, which is independent of the supply voltage. This characteristic may have a negative effect on the stability of a power supply system. In addition real Constant-Power-Loads can have some other peculiarities. Depending of the topology or the supplied voltage type (AC or DC) the dynamic characteristic differs. This paper deals with a characterization of 4 types of Constant-Power-Loads in an actual and future aircraft grid. The investigations are focused to the dynamic characterization of different loads. Theoretical investigations are combined with measurements in an artificial aircraft grid with realistic supply voltage variations.

Implementation of a Solid-State Power Controller for High-Voltage DC Grids in Aircraft

Conventional electrical distribution systems onboard aircraft use a three-phase system with a typical voltage of 115 VAC or 230 VAC to supply electrical loads. Future aircraft demand more electric power due to the replacement of hydraulic and pneumatic systems by electrical ones and the increased use of multimedia entertainment systems. However, the aircraft weight can be decreased if a high-voltage direct current (HVDC) grid with a voltage level of ±270 VDC or 540 VDC is implemented to supply the electrical loads. These higher voltages reduce cable weight, but are a new challenge for solid-state power controllers (SSPC), which are used as protection devices for cables and loads. Currently available SSPCs are limited to lower voltages and currents mainly because of the available power semiconductors. A SSPC for aircraft applications with a nominal voltage of 540 VDC and a nominal load current of 10 A has been developed at the Helmut Schmidt University in Hamburg in cooperation with Airbus Group Innovation using SiC-MOSFETs and has been tested. In this paper the design and experimental results are presented. The SSPC is able to supply itself from the high voltage autarkic and can accomplish various functions.

Graphical analysis method to identify power -balanced grid areas for intended islanding operation

The increasing number of decentralized power generators in the low-voltage and medium-voltage grid induce multiple short-time power- balanced areas. These areas intensify the problem to determine the dynamic energy flow of the distribution grid. The identification of power- balanced grid parts is a time consuming and computationally intensive process. Hence, this contribution presents a simplified identification method that has minor computational effort. The method computes a simplified energy flow over more than one voltage level. So, it is even possible to identify power- balanced grid parts that are spread over different voltage levels. For evaluation and validation the method is compared to a traditional grid simulation with DIgSILENT PowerFactory.

Influence of grid-connected solar inverters and mains monitoring systems on the spectral grid impedance

The impact of harmonic distortion on the power quality, caused by solar inverters, is strongly affected by the spectral characteristic of the grid impedance at the point of common coupling (PCC). The grid impedance at a PCC can be modelled as a parallel connection of the equivalent impedances of the grid structure and the solar inverter system. Yet, it is challenging to determine the exact frequency characteristics of these parameters. It requires detailed spectral models, which are often not available especially for the grid. In this contribution, both parameters are measured and evaluated in the frequency range from DC up to 20 kHz. In order to analyse the impact, the impedance is measured on a test grid structure and a PCC. In particular, this paper analyses the influence of the number of parallel-connected inverters as well as the operation point and the integrated mains monitoring system on the resulting spectral grid impedance.

Die Bundeswasserstraßen als Energiespeicher — Potenzial und Herausforderungen@@@The Federal Waterways as Energy Storage System — Potential and Challenges@@@Водные пути федерального значения как накопители энергии – потенциал и проблемы

Für die Speicherung von Überschüssen aus uktuierenden erneuerbaren Energien ist das Pumpspeicherwerk (PSW) momentan die einzige großtechnisch realisierbare Speichertechnologie. PSW sind technisch ausgereift und sind bei passenden Randbedingungen wirtschaftlich zu betreiben. Konventionelle PSW benötigen geeignete, in Deutschland aber begrenzt vorhandene geologische Rahmenbedingungen. Durch die Nutzung schon bestehender künstlicher Strukturen können neue Speicherkapazitäten erschlossen werden, wie hier am Beispiel der Bundeswasserstraßen gezeigt wird.

Self-testing Solid-State Power Controller for High-Voltage-DC Aircraft Applications

Nowadays solid-state power controllers (SSPC) are widely used in aircraft secondary power supply, because of a higher count of switching cycles, small weight, flexible trip behavior, and a fieldbus connection. Typically, they protect loads and their connection lines. One drawback of these solid-state switches is the typical 28V secondary power supply for the control elements. This paper shows an effective supply arrangement to use the onboard power supply as energy source. Parallel MOSFETs represent the switching unit. This can be used for a self-test without supply interruption of connected loads. A self-test method is shown in this paper.

Simultaneous Implementation of LVRT Capability and Anti-Islanding Detection in Three-Phase Inverters Connected to Low-Voltage Grids

In the future, the provision of ancillary services in low-voltage grids will become more and more important. Low-voltage ride-through capability has been a requirement in medium- and high-voltage grids but will become mandatory even in low-voltage grids. There may be conflicts with existing requirements such as anti-islanding detection. This paper proposes a method that allows for both low-voltage ride-through capability and anti-islanding protection to be implemented simultaneously in three-phase inverters connected to low-voltage grids. This method uses constant voltage and frequency monitoring and reacts according to the relevant specific requirements. With the proposed method, inverters can contribute to system stability without the risk of unintentional islanding operation. The implementation of low-voltage ride-through capability is shown to even facilitate the detection of islanded grids. To prove the merit of this proposal, a model for a three-phase inverter is developed, which incorporates the proposed method and is successfully tested both in simulation and in experiments in the laboratory.

Umbau des Energiesystems, virtuelle Kraftwerke und Kanalpumpspeicher

Seit der Liberalisierung der Energiemarkte und den sicherheits- und klimapolitisch motivierten Planen zur Erhohung des Anteils erneuerbarer Energien befinden sich Energiedargebot und Energiemarkte in einem grundlegenden Wandel. Zur Angleichung von Energiedargebot und -nachfrage werden bei einem wachsenden Anteil flukturierender erneuerbarer Energien Optionen zur Flexibilisierung benotigt, zu denen Speicher zahlen. In der vorliegenden Untersuchung wird der Frage nachgegangen, inwieweit das bestehende Netz der Bundeswasserstrasen dazu geeignet ist, als grostechnischer Energiespeicher zu fungieren. Es wird nach einer Losung gesucht, eine technologisch ausgereifte Speicherform fur elektrische Energie, ein Pumpspeicherkraftwerk, in eine Verbindung mit regionalen Gegebenheiten und moglichst geringen Investitions- und/oder Betriebskosten zu bringen. Der Vorteil eines Pumpspeicherwerks in kunstlichen Strukturen wie Kanalen liegt darin, dass auf eine vorhandene Infrastruktur zuruckgegriffen wird. Der zusatzliche Eingriff in die Landschaft ist somit gering. Im ersten Kapitel wird nach den einfuhrenden Worten (1.1) der Projekthintergrund erlautert (1.2). Das Buch ist im Rahmen des von der EU und dem Land Niedersachsen geforderten Forschungsprojekts EnERgioN entstanden. Hiernach werden Fragestellung und Aufbau des Buches erlautert (1.3).