Ines Hauer

Transmission properties of a 1D resonant cavity

Acoustic band gap materials, so-called phononic crystals, provide a new platform for sensing material properties in small cavities. The sensor employs a specific feature of the band gap to determine properties of one component that builds the phononic crystal. The dependence of the frequency within the band gap where transmission takes place due to a resonant mode in the cavity is correlated to material properties. The capability of this concept will be demonstrated with a one-dimensional periodic arrangement of solid plates and liquid filled cavities. The properties of this 1D phononic crystal will be analyzed in terms of its effective acoustic impedance and the resulting transmission properties and experimentally verified.

Smart grid in critical situations. Do we need some standards for this? A german perspective

The power system is changing rapidly due to the wide integration of renewable energy sources. In order to ensure a secure energy supply in the future power system (smart grid) the current laws, rules and standards concerning measures in critical system states to save or re-establish the system need to be examined. In this paper the authors provide a definition of critical states in the electric power system and describe measures to react in critical states or to prevent system instability based on current rules in Europe and Germany. The study aims to identify the demand for standardization in this area.

Concept, architecture and components of a smart distribution control center

The power system, especially on the distribution level, is subject to different changes due to transition process to renewable energies. On the other hand customers receive more possibilities to operate actively with the local system. In this paper a concept of a future control center for the smart distribution energy systems is presented to meet these challenges. Starting with an overview of future tasks a proposed architecture of a future distribution system is shown. The new components that are need for distribution system automation are introduced and modeled in HTML in detail. An overview of future services like full observability is given and components that are incorporated into the power system are described. An execution of the data management of such complex systems requires standardized plug in protocols, i.e. IEC 61850 and IEC 61970. This most relevant aspect is prioritized also in this paper. Finally a structure of a smart control center for future distribution systems is given.

Use of multifunctional power electronic network controllers in smart distribution systems

Diverse and dynamic load and generation patterns are putting new demands on the operation of distribution networks. New network management approaches and innovative equipment are needed to handle highly volatile voltage profiles resulting from intermittent distributed generation. This paper investigates the use of an inline voltage regulator in a LV network. As simulations based on realistic feed-in scenarios show, it is an efficient tool for influencing a networks voltage profile. Since voltage regulation is not required permanently, such a flexible power electronic device can be further used to increase a power systems efficiency and reliability by implementing features such as reactive power compensation or mitigation of harmonics. Concerning this matter, an approach for an adaptive system management is discussed that allows the provision of additional functionality whenever the converter is not used to its full capacity for the voltage regulation task.

Communication interface requirements during critical situations in a Smart Grid

The power system is changing rapidly also due to the wide integration of renewable energy sources, mostly in the distribution grid. In order to ensure a secure energy supply today and especially in the future power system (Smart Grid) the current laws, rules and standards need to be examined concerning measures in critical system states to save or re-establish the system. In this paper the authors justify the standardization demand focusing on the expanded data exchange between TSO and DSO and propose a common communication concept according to IEC 61968/70.

Technical integration of virtual power plants into German system operation

This paper critically evaluates the operational perspective of Virtual Power Plants (VPP) in Germany by analyzing key factors to replace conventional power plants in the future power system. Therefore, its necessity for the secure operation as well as the technical and economic benefits for the German power system are pointed out. The single sections describe in detail how the requirements on technical functions and standardized communication can be reconciled with the increasing challenges on volatile generation. Furthermore, a new sensitivity calculation concept based on accounting areas and under consideration of VPP are presented. Based on that, different operation concepts are assessed with respect to their mathematical algorithms and their practical feasibility under consideration of given circumstances and future developments.

Optimal tariff system for integration of distributed resources based on a comparison of Brazil's and Germany's system

The energy trading in Brazil is conducted in two different environments: the Free Market (ACL) and the Regulated Market (ACR). In ACL, the free and specials consumers can freely negotiate their own energy. In contrast, the captive consumers belong to ACR, and do not have the option to choose their energy supplier. Germany also has a similar system, where the big consumers (industrial) can freely negotiate their energy and the small consumers (residential) must choose a provider and pay a fixed price for the energy, where prices vary very little from one provider to another. Recently in Brazil, it was created the white tariff providing conditions that stimulate some consumers to shift consumption from peak periods to those periods that the distribution network has idle capacity. Regarding distributed energy resources (DER), there are also some peculiarities between the two countries. The objective of this paper is to verify the impacts that German residential consumers and the distribution network would have with the implementation of an hourly tariff equivalent to the white tariff of Brazil. The tariff structure and energy market regulation from both countries are compared and several simulations considering real data from German consumers and tariffs are done.

Lastabwurfkonzept auf Basis von Jahresmittelwerten

Kurzfassung — Vor dem Hintergrund des steigenden Anteils von erneuerbaren Erzeugungsanlagen im Netz werden immer mehr konzeptionelle Anpassungen zur Sicherstellung der Systemstabilität notwendig, um z.B. einen vermehrten Leistungsfluss vom Verteilungsnetz zum Übertragungsnetz zu berücksichtigen. Die vorgestellten Untersuchungen befassen sich speziell mit dem frequenzabhängigen automatischen Lastabwurf gemäß eines modifizierten 5-Stufenplans zur Behebung der Unterfrequenz. Da die Schutzsysteme bzw. die Frequenzrelais unabhängig von der Lastflussrichtung automatisch auslösen, kann es im Problemfall dazu kommen, dass anstatt Lasten Erzeugungsanlagen vom Netz getrennt werden. Für die Lösung dieser Problematik wurde in den Untersuchungen ein neues, alternatives Lastabwurfkonzept auf Basis von Jahresmittelwerten analysiert und unter Anwendung verschiedener Szenarien an einem Netzmodell getestet. Dafür wurden auf Grundlage einer gegebenen Datenbasis der 50Hertz Transmission GmbH Referenzwerte je Transformator und anschließend die Wahrscheinlichkeit, dass an einem Transformator die geforderte Last abgeschaltet werden kann, ermittelt. Weiterhin werden Lastabwurf und Erzeugerzeitreihen berechnet sowie eine Lastabschätzung für jedes Szenario vorgenommen und in das Modell implementiert. Das Paper bietet abschließend einen qualitativen Vergleich des aktuellen Lastabwurfkonzepts auf Basis der Jahreshöchstlast mit dem neuen Konzept auf Basis des Jahresmittelwerts.

Dimensioning of the peripheral components for a fuel cell based auxiliary power unit in vehicle electrical system

The increasing demand of electrical energy in automobiles has led to the problem that the vehicle electrical system does not get enough energy from the generator. Therefore, an additional energy converter is needed to supply the system with the higher demand. A fuel cell system can be used as an additional converter. However, this fuel cell system needs a lot of peripheral components in order to operate. This paper presents the investigation of the peripheral components of such a fuel cell system as an auxiliary power unit (APU) in the vehicle electrical system. A model of a fuel cell system was designed to determine the peripheral power requirement of PEM fuel cell systems between 300 W and 5 kW. For this purpose, appropriate electric factors of different performance classes were selected on the basis of measurements and data sheets. The result produced is the net power that can be made available for the connected vehicle electrical distribution system. On average, one should budget for 20% of the maximum output to be used by the peripheral power supply and power adjustment.