Resilience of data centre power system: modelling of sustained operation under outage, definition of metrics, and application

A novel criterion for quantifying the resilience of power systems supplying data centres is formulated to measure the system's ability to sustain functionality even during an outage. By comparative analysis of two alternative data centre power systems covering apparatus of electrical power supply and environmental control, it is shown that reliability and availability alone are insufficient as metrics to gauge different designs. The gap is bridged by the proposed resilience analysis to further evaluate situations of single and double outages. As a complement to the indicators of single point of failure and double point of failure, respectively, N−1 and N−2 security criteria, the novel metrics of a single point of reduced availability and double point of reduced availability are proposed. These criteria identify those single subsystems or subsystem pairs causing system availability to drop below requested levels in periods when they are out of service. The metrics so offer information on the overall system's availability during times of maintenance and failures. Thanks to this understanding, it is shown that a guided reduction of the number of subsystems considering their relative importance can lead to designs offering desirable trade-offs in terms of complexity, reliability, availability, and resilience.DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli

Smart Grid: The Central Nervous System for Power Supply : New Paradigms, New Challenges, New Services

Im Energiesystem der Zukunft wird ein intelligentes Netz (Smart Grid) Angebot und Nachfrage effizient steuern. Dieser Artikel beschreibt (1) die Trends und Herausforderungen heutiger Ener-giesysteme, die die Entwicklung eines Smart Grid auslösen, identifiziert (2) Elemente eines Smart Grid und stellt (3) die mögliche Rolle eines Telekommunkationsunternehmes im entste-henden Smart Grid Markt dar. Der Trend zu einem steigenden Anteil erneuerbarer und dezentraler Energieerzeugungsanlagen bringt zwei große Herausforderungen mit sich: Eine mangelnde Vorhersagbarkeit und eine man-gelnde Regelbarkeit der Erzeugungsleistung. In diesem Artikel werden vier Elemente eines Smart Grid vorgestellt, die diese Herausforderungen adressieren: Virtuelle Kraftwerke, Demand Side Management, Lastflussregelung und Energiespeicherung. Abschließend wird herausgestellt, dass die Elemente systemisch integiert werden müssen um den eigentlichen Wert des Smart Grid zu heben. Es wird erörtert, dass sich Telekommunkiationsan-bieter in einer guten Ausgangsposition befinden um die Herausforderungen dieser Integration zu adressieren, da sie über wesentliche Erfahrungen und Fähigkeiten verfügen: Umfassendes Ver-ständnis großer IP-Netzwerke, Erfahrungen mit Cloud Computing, umfangreiches Wissen zu Service-Plattformen und Kooperationserfahrung. Online-Version im Universitätsverlag der TU Berlin (www.univerlag.tu-berlin.de) erschienen.In future power systems, a smart grid is expected to manage supply and demand of electricity efficiently. This article explores (1) the trends and challenges of today’s power system that trig-ger the development of smart grids, (2) the elements that may eventually constitute the smart grid and (3) the role a telcommunication provider may adopt in the emerging smart grid market. The trend towards an increasing share of renewable and distributed energy sources bears two major challenges: A lack of predictability and a lack of controllability of power generation. This article introduces four elements of a smart grid which address these challenges: virtual power plants, demand side management, control of power flow and storage and buffering. Finally, it is pointed out that in order to enhance the smart grid’s actual value, the elements have to be systemically integrated. It is argued that telecommunication providers are well positioned to adress the integration challenges as they have crucial experiences and capabilities: profound understanding of large IP networks, experiences in cloud computing, extensive service platform know-how and cooperation experience. Online-Version published by Universitätsverlag der TU Berlin (www.univerlag.tu-berlin.de

Wavelet-Based Harmonic Magnitude Measurement in the Presence of Interharmonics

The increasing proliferation of power electronic converters, nonlinear loads, and distributed generation are leading to increased levels of harmonic and interharmonics in power networks. As a consequence, power quality (PQ) has become a critical performance indicator for power utilities and end-users. This study proposes a novel harmonic estimation method based on the real-time stationary discrete wavelet packet transform (RT-SDWPT). The proposed technique decomposes an input signal into frequency bands with harmonic information at cutoff frequencies and uses a compensation strategy to estimate root mean square (RMS) values of harmonics at every sampling period. The performance and effectiveness of the proposed method are assessed using real measurement data from field cases and experimental setup. The real measurements include challenging scenarios with harmonics, subharmonics, interharmonics, frequency deviation, and non-stationary PQ events. The proposed method outperforms the harmonic estimation provided by the discrete Fourier transform (DFT)-based approach and existing wavelet packet-based methods in terms of accuracy and speed

Assessment of human immediate response capability related to tsunami threats in Indonesia at a sub-national scale

Human immediate response is contextualized into different time compartments reflecting the tsunami early warning chain. Based on the different time compartments the available response time and evacuation time is quantified. The latter incorporates accessibility of safe areas determined by a hazard assessment, as well as environmental and demographic impacts on evacuation speed properties assessed using a Cost Distance Weighting GIS approach. Approximately 4.35 million Indonesians live in tsunami endangered areas on the southern coasts of Sumatra, Java and Bali and have between 20 and 150 min to reach a tsunami-safe area. Most endangered areas feature longer estimated-evacuation times and hence the population possesses a weak immediate response capability leaving them more vulnerable to being directly impacted by a tsunami. At a sub-national scale these hotspots were identified and include: the Mentawai islands off the Sumatra coast, various sub-districts on Sumatra and west and east Java. Based on the presented approach a temporal dynamic estimation of casualties and displacements as a function of available response time is obtained for the entire coastal area. As an example, a worst case tsunami scenario for Kuta (Bali) results in casualties of 25 000 with an optimal response time (direct evacuation when receiving a tsunami warning) and 120 000 for minimal response time (no evacuation). The estimated casualties correspond well to observed/reported values and overall model uncertainty is low with a standard error of 5%. The results obtained allow for prioritization of intervention measures such as early warning chain, evacuation and contingency planning, awareness and preparedness strategies down to a sub-district level and can be used in tsunami early warning decision support

Non-Markovian Quantum Dynamics in Strongly Coupled Multimode Cavities Conditioned on Continuous Measurement

An important challenge in non-Markovian open quantum systems is to understand what information we gain from continuous measurement of an output field. For example, atoms in multimode cavity QED systems provide an exciting platform to study many-body phenomena in regimes where the atoms are strongly coupled amongst themselves and with the cavity, but the strong coupling makes it complicated to infer the conditioned state of the atoms from the output light. In this work we address this problem, describing the reduced atomic state via a conditioned hierarchy of equations of motion, which provides an exact conditioned reduced description under monitoring (and continuous feedback). We utilize this formalism to study how different monitoring for modes of a multimode cavity affects our information gain for an atomic state, and to improve spin squeezing via measurement and feedback in a strong coupling regime. This work opens opportunities to understand continuous monitoring of non-Markovian open quantum systems, both on a practical and fundamental level