Wednesday, 13 December 2017

Session 1: Tutorials

Holistic Optimization of Distribution Automation Network Designs Using Survivability Modeling and Power Flow Equations

Authors:

Anne Koziolek (University of Zurich)
Alberto Avritzer (Siemens Corporation)
Daniel Sadoc Menasché (Federal University of Rio de Janeiro)

Abstract:

Smart grids are fostering a paradigm shift in the realm of power distribution systems. Whereas traditionally different components of the power distribution system have been provided and analyzed by different teams, smart grids require a unified and holistic approach taking into consideration the interplay of distributed generation, distribution automation topology, intelligent features, and others.

In this tutorial, we present how transient survivability metrics can be used to create better distribution automation network designs. Our approach combines survivability analysis and power flow analysis to assess the survivability of the distribution power grid network.

We first describe the reliability challenges power utilities face and discuss the additional challenges and opportunities introduced by a smarter grid with features such as fault detection, isolation, and restoration. We then lay the foundations by introducing relevant reliability metrics and by putting survivability metrics into the broader context of dependability metrics.

We then describe how two complex systems such as a telecommunications server and a smart grid distribution automation grid could be modelled using survivability metrics. Specifically, we show how a smart grid distribution automation grid can be modelled in an abstract way using a Markov reward model and how this model is parameterized with results from power flow analysis and measured data from the utility.

Finally, we present an initial approach to automatically optimize available investment decisions with respect to survivability and investment costs and highlight its benefits by applying it to the design of a real distribution automation circuit.

DOI: 10.1145/2479871.2479873

Full text: PDF

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Use Case-Driven Performance Engineering without "Concurrent Users"

Authors:

Morten Heine Sørensen (Formalit)

Abstract:

The concept of concurrent users often causes confusion when used to define performance requirements in industrial software projects. The term is frequently used to state performance requirements without clarification of what the users will be doing, or how often. This paper offers a thorough analysis of the concept and related notions. Despite the confusion surrounding it, the concept of concurrent users – in a precise form – is advocated in the community for stating performance requirements. However, we argue in this paper that, even when stated in precise terms, this approach has drawbacks. Indeed, a system may perform better than expected, even if the number of concurrent users it can handle is worse than expected. A better suited notion is that of through-put. But even when basing performance requirements on clear, well-suited concepts, there appears to be no uniform format in the literature for such requirements. In particular, the requirements are sometimes stated in general, rather than for the specific areas of functionality of the system. As a consequence, the point may be missed that the through-put may be unevenly distributed over the functionality of the system. In this paper we therefore advocate the format of performance-annotated use cases, adding requirements on through-put and response-time to the traditional use case. It is well-known how functional test cases are developed from use cases. In contrast, less has been said about the generation of performance test cases. Therefore, we show how the enriched use cases not only provide precise and meaningful requirements, but also yield detailed specification of the performance test set-up which can be directly input as configuration of load test clients. As a bonus, initial configuration of the system’s capacity for handling concurrent users and requests is also provided. Finally we outline an overall approach to performance test based on the above ideas. The approach has been followed in several industrial projects.

DOI: 10.1145/2479871.2479874

Full text: PDF

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