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  1. Article ; Online: Predicting dynamic stability from static features in power grid models using machine learning.

    Titz, Maurizio / Kaiser, Franz / Kruse, Johannes / Witthaut, Dirk

    Chaos (Woodbury, N.Y.)

    2024  Volume 34, Issue 1

    Abstract: A reliable supply with electric power is vital for our society. Transmission line failures are among the biggest threats for power grid stability as they may lead to a splitting of the grid into mutual asynchronous fragments. New conceptual methods are ... ...

    Abstract A reliable supply with electric power is vital for our society. Transmission line failures are among the biggest threats for power grid stability as they may lead to a splitting of the grid into mutual asynchronous fragments. New conceptual methods are needed to assess system stability that complement existing simulation models. In this article, we propose a combination of network science metrics and machine learning models to predict the risk of desynchronization events. Network science provides metrics for essential properties of transmission lines such as their redundancy or centrality. Machine learning models perform inherent feature selection and, thus, reveal key factors that determine network robustness and vulnerability. As a case study, we train and test such models on simulated data from several synthetic test grids. We find that the integrated models are capable of predicting desynchronization events after line failures with an average precision greater than 0.996 when averaging over all datasets. Learning transfer between different datasets is generally possible, at a slight loss of prediction performance. Our results suggest that power grid desynchronization is essentially governed by only a few network metrics that quantify the networks' ability to reroute the flow without creating exceedingly high static line loadings.
    Language English
    Publishing date 2024-01-25
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1472677-4
    ISSN 1089-7682 ; 1054-1500
    ISSN (online) 1089-7682
    ISSN 1054-1500
    DOI 10.1063/5.0175372
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Optimizing the geometry of transportation networks in the presence of congestion.

    Dahlmanns, Matthias / Kaiser, Franz / Witthaut, Dirk

    Physical review. E

    2023  Volume 108, Issue 4-1, Page(s) 44302

    Abstract: Urban transport systems are gaining in importance, as an increasing share of the global population lives in cities and mobility-based carbon emissions must be reduced to mitigate climate change and improve air quality and citizens' health. As a result, ... ...

    Abstract Urban transport systems are gaining in importance, as an increasing share of the global population lives in cities and mobility-based carbon emissions must be reduced to mitigate climate change and improve air quality and citizens' health. As a result, public transport systems are prone to congestion, raising the question of how to optimize them to cope with this challenge. In this paper, we analyze the optimal design of urban transport networks to minimize the average travel time in monocentric as well as in polycentric cities. We suggest an elementary model for congestion and introduce a numerical method to determine the optimal shape among a set of predefined geometries considering different models for the behavior of individual travelers. We map out the optimal shape of fundamental network geometries with a focus on the impact of congestion.
    Language English
    Publishing date 2023-11-17
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2844562-4
    ISSN 2470-0053 ; 2470-0045
    ISSN (online) 2470-0053
    ISSN 2470-0045
    DOI 10.1103/PhysRevE.108.044302
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Book ; Online ; Thesis: Agent-based Studies of Collective Phenomena in Supply Network Operation

    Han, Chengyuan [Verfasser] / Witthaut, Dirk [Gutachter] / Schadschneider, Andreas [Gutachter]

    2024  

    Author's details Chengyuan Han ; Gutachter: Dirk Witthaut, Andreas Schadschneider
    Keywords Wirtschaft ; Economics
    Subject code sg330
    Language English
    Publisher Universitäts- und Stadtbibliothek Köln
    Publishing place Köln
    Document type Book ; Online ; Thesis
    Database Digital theses on the web

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  4. Article ; Online: Dynamic stability of electric power grids: Tracking the interplay of the network structure, transmission losses, and voltage dynamics.

    Böttcher, Philipp C / Witthaut, Dirk / Rydin Gorjão, Leonardo

    Chaos (Woodbury, N.Y.)

    2022  Volume 32, Issue 5, Page(s) 53117

    Abstract: Dynamic stability is imperative for the operation of the electric power system. This article provides analytical results and effective stability criteria focusing on the interplay of network structures and the local dynamics of synchronous machines. The ... ...

    Abstract Dynamic stability is imperative for the operation of the electric power system. This article provides analytical results and effective stability criteria focusing on the interplay of network structures and the local dynamics of synchronous machines. The results are based on an extensive linear stability analysis of the third-order model for synchronous machines, comprising the classical power-swing equations and the voltage dynamics. The article addresses the impact of Ohmic losses, which are important in distribution and microgrids but often neglected in analytical studies. We compute the shift of the stability boundaries to leading order, and thus provide a detailed qualitative picture of the impact of Ohmic losses. A subsequent numerical study of the criteria is presented, without and with resistive terms, to test how tight the derived analytical results are.
    Language English
    Publishing date 2022-04-11
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1472677-4
    ISSN 1089-7682 ; 1054-1500
    ISSN (online) 1089-7682
    ISSN 1054-1500
    DOI 10.1063/5.0082712
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Book ; Online: Stability bounds of droop-controlled inverters in power grid networks

    Böttcher, Philipp C. / Gorjão, Leonardo Rydin / Witthaut, Dirk

    2023  

    Abstract: The energy mix of future power systems will include high shares of wind power and solar PV. These generation facilities are generally connected via power-electronic inverters. While conventional generation responds dynamically to the state of the ... ...

    Abstract The energy mix of future power systems will include high shares of wind power and solar PV. These generation facilities are generally connected via power-electronic inverters. While conventional generation responds dynamically to the state of the electric power system, inverters are power electronic hardware and need to be programmed to react to the state of the system. Choosing an appropriate control scheme and the corresponding parameters is necessary to guarantee that the system operates safely. A prominent control scheme for inverters is droop control, which mimics the response of conventional generation. In this work, we investigate the stability of coupled systems of droop-controlled inverters in arbitrary network topologies. Employing linear stability analysis, we derive effective local stability criteria that consider both the overall network topology as well as its interplay with the inverters' intrinsic parameters. First, we explore the stability of an inverter coupled to an infinite grid in an analytic fashion and uncover stability and instability regions. Secondly, we extend the analysis to a generic topology of inverters and provide mathematical criteria for stability and instability of the system. Last, we showcase the usefulness of the criteria by examining two model systems using numerical simulations. The developed criteria show which parameters might lead to an unstable operating state.

    Comment: 13 pages, 7 figures
    Keywords Electrical Engineering and Systems Science - Systems and Control ; Physics - Physics and Society
    Subject code 621
    Publishing date 2023-03-29
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Article ; Online: Network isolators inhibit failure spreading in complex networks.

    Kaiser, Franz / Latora, Vito / Witthaut, Dirk

    Nature communications

    2021  Volume 12, Issue 1, Page(s) 3143

    Abstract: In our daily lives, we rely on the proper functioning of supply networks, from power grids to water transmission systems. A single failure in these critical infrastructures can lead to a complete collapse through a cascading failure mechanism. ... ...

    Abstract In our daily lives, we rely on the proper functioning of supply networks, from power grids to water transmission systems. A single failure in these critical infrastructures can lead to a complete collapse through a cascading failure mechanism. Counteracting strategies are thus heavily sought after. In this article, we introduce a general framework to analyse the spreading of failures in complex networks and demostrate that not only decreasing but also increasing the connectivity of the network can be an effective method to contain damages. We rigorously prove the existence of certain subgraphs, called network isolators, that can completely inhibit any failure spreading, and we show how to create such isolators in synthetic and real-world networks. The addition of selected links can thus prevent large scale outages as demonstrated for power transmission grids.
    Language English
    Publishing date 2021-05-25
    Publishing country England
    Document type Journal Article
    ZDB-ID 2553671-0
    ISSN 2041-1723 ; 2041-1723
    ISSN (online) 2041-1723
    ISSN 2041-1723
    DOI 10.1038/s41467-021-23292-9
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article ; Online: Revealing drivers and risks for power grid frequency stability with explainable AI.

    Kruse, Johannes / Schäfer, Benjamin / Witthaut, Dirk

    Patterns (New York, N.Y.)

    2021  Volume 2, Issue 11, Page(s) 100365

    Abstract: Stable operation of an electric power system requires strict operational limits for the grid frequency. Fluctuations and external impacts can cause large frequency deviations and increased control efforts. Although these complex interdependencies can be ... ...

    Abstract Stable operation of an electric power system requires strict operational limits for the grid frequency. Fluctuations and external impacts can cause large frequency deviations and increased control efforts. Although these complex interdependencies can be modeled using machine learning algorithms, the black box character of many models limits insights and applicability. In this article, we introduce an explainable machine learning model that accurately predicts frequency stability indicators for three European synchronous areas. Using Shapley additive explanations, we identify key features and risk factors for frequency stability. We show how load and generation ramps determine frequency gradients, and we identify three classes of generation technologies with converse impacts. Control efforts vary strongly depending on the grid and time of day and are driven by ramps as well as electricity prices. Notably, renewable power generation is central only in the British grid, while forecasting errors play a major role in the Nordic grid.
    Language English
    Publishing date 2021-10-08
    Publishing country United States
    Document type Journal Article
    ISSN 2666-3899
    ISSN (online) 2666-3899
    DOI 10.1016/j.patter.2021.100365
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Book ; Online: Regulatory Changes in Power Systems Explored with Explainable Artificial Intelligence

    Pütz, Sebatian / Kruse, Johannes / Witthaut, Dirk / Hagenmeyer, Veit / Schäfer, Benjamin

    2023  

    Abstract: A stable supply of electrical energy is essential for the functioning of our society. Therefore, the electrical power grid's operation and energy and balancing markets are subject to strict regulations. As the external technical, economic, or social ... ...

    Abstract A stable supply of electrical energy is essential for the functioning of our society. Therefore, the electrical power grid's operation and energy and balancing markets are subject to strict regulations. As the external technical, economic, or social influences on the power grid change, these regulations must also be constantly adapted. However, whether these regulatory changes lead to the intended results is not easy to assess. Could eXplainable Artificial Intelligence (XAI) models distinguish regulatory settings and support the understanding of the effects of these changes? In this article, we explore two examples of regulatory changes in the German energy markets for bulk electricity and for reserve power. We explore the splitting of the German-Austrian bidding zone and changes in the pricing schemes of the German balancing energy market. We find that boosted tree models and feedforward neural networks before and after a regulatory change differ in their respective parametrizations. Using Shapley additive explanations, we reveal model differences, e.g. in terms of feature importances, and identify key features of these distinct models. With this study, we demonstrate how XAI can be applied to investigate system changes in power systems.

    Comment: 7 pages, 3 figures
    Keywords Electrical Engineering and Systems Science - Systems and Control
    Subject code 303
    Publishing date 2023-03-30
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  9. Book ; Online: Multivariate Probabilistic Forecasting of Intraday Electricity Prices using Normalizing Flows

    Cramer, Eike / Witthaut, Dirk / Mitsos, Alexander / Dahmen, Manuel

    2022  

    Abstract: Electricity is traded on various markets with different time horizons and regulations. Short-term intraday trading becomes increasingly important due to the higher penetration of renewables. In Germany, the intraday electricity price typically fluctuates ...

    Abstract Electricity is traded on various markets with different time horizons and regulations. Short-term intraday trading becomes increasingly important due to the higher penetration of renewables. In Germany, the intraday electricity price typically fluctuates around the day-ahead price of the European Power EXchange (EPEX) spot markets in a distinct hourly pattern. This work proposes a probabilistic modeling approach that models the intraday price difference to the day-ahead contracts. The model captures the emerging hourly pattern by considering the four 15 min intervals in each day-ahead price interval as a four-dimensional joint probability distribution. The resulting nontrivial, multivariate price difference distribution is learned using a normalizing flow, i.e., a deep generative model that combines conditional multivariate density estimation and probabilistic regression. Furthermore, this work discusses the influence of different external impact factors based on literature insights and impact analysis using explainable artificial intelligence (XAI). The normalizing flow is compared to an informed selection of historical data and probabilistic forecasts using a Gaussian copula and a Gaussian regression model. Among the different models, the normalizing flow identifies the trends with the highest accuracy and has the narrowest prediction intervals. Both the XAI analysis and the empirical experiments highlight that the immediate history of the price difference realization and the increments of the day-ahead price have the most substantial impact on the price difference.

    Comment: manuscript (20 pages, 11 figures, 5 tables), supporting information (8 pages, 5 figures, 4 tables)
    Keywords Computer Science - Machine Learning
    Subject code 330
    Publishing date 2022-05-27
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  10. Book ; Online: Revealing interactions between HVDC cross-area flows and frequency stability with explainable AI

    Pütz, Sebastian / Schäfer, Benjamin / Witthaut, Dirk / Kruse, Johannes

    2022  

    Abstract: The energy transition introduces more volatile energy sources into the power grids. In this context, power transfer between different synchronous areas through High Voltage Direct Current (HVDC) links becomes increasingly important. Such links can ... ...

    Abstract The energy transition introduces more volatile energy sources into the power grids. In this context, power transfer between different synchronous areas through High Voltage Direct Current (HVDC) links becomes increasingly important. Such links can balance volatile generation by enabling long-distance transport or by leveraging their fast control behavior. Here, we investigate the interaction of power imbalances - represented through the power grid frequency - and power flows on HVDC links between synchronous areas in Europe. We use explainable machine learning to identify key dependencies and disentangle the interaction of critical features. Our results show that market-based HVDC flows introduce deterministic frequency deviations, which however can be mitigated through strict ramping limits. Moreover, varying HVDC operation modes strongly affect the interaction with the grid. In particular, we show that load-frequency control via HVDC links can both have control-like or disturbance-like impacts on frequency stability.

    Comment: 14 pages, 8 figures; submitted version
    Keywords Electrical Engineering and Systems Science - Systems and Control ; Computer Science - Artificial Intelligence ; Physics - Data Analysis ; Statistics and Probability
    Subject code 612
    Publishing date 2022-04-22
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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