Towards Distributed OPF using ALADIN

The present paper discusses the application of the recently proposed Augmented Lagrangian Alternating Direction Inexact Newton (ALADIN) method to non-convex AC Optimal Power Flow Problems (OPF) in a distributed fashion. In contrast to the often used Alternating Direction of Multipliers Method (ADMM), ALADIN guarantees locally quadratic convergence for AC OPF. Numerical results for 5 to 300 bus test cases indicate that ALADIN is able to outperform ADMM and to reduce the number of iterations by about one order of magnitude. We compare ALADIN to numerical results for ADMM documented in the literature. The improved convergence speed comes at the cost of increasing the communication effort per iteration. Therefore, we propose a variant of ALADIN that uses inexact Hessians to reduce communication. Additionally, we provide a detailed comparison of these ALADIN variants to ADMM from an algorithmic and communication perspective. Moreover, we prove that ALADIN converges locally at quadratic rate even for the relevant case of suboptimally solved local NLPs

Distributed State Estimation for AC Power Systems using Gauss-Newton ALADIN

This paper proposes a structure exploiting algorithm for solving non-convex power system state estimation problems in distributed fashion. Because the power flow equations in large electrical grid networks are non-convex equality constraints, we develop a tailored state estimator based on Augmented Lagrangian Alternating Direction Inexact Newton (ALADIN) method, which can handle the nonlinearities efficiently. Here, our focus is on using Gauss-Newton Hessian approximations within ALADIN in order to arrive at at an efficient (computationally and communicationally) variant of ALADIN for network maximum likelihood estimation problems. Analyzing the IEEE 30-Bus system we illustrate how the proposed algorithm can be used to solve highly non-trivial network state estimation problems. We also compare the method with existing distributed parameter estimation codes in order to illustrate its performance

Consensus ALADIN: A Framework for Distributed Optimization and Its Application in Federated Learning

This paper investigates algorithms for solving distributed consensus optimization problems that are non-convex. Since Typical ALADIN (Typical Augmented Lagrangian based Alternating Direction Inexact Newton Method, T-ALADIN for short) [1] is a well-performed algorithm treating distributed optimization problems that are non-convex, directly adopting T-ALADIN to those of consensus is a natural approach. However, T-ALADIN typically results in high communication and computation overhead, which makes such an approach far from efficient. In this paper, we propose a new variant of the ALADIN family, coined consensus ALADIN (C-ALADIN for short). C-ALADIN inherits all the good properties of T-ALADIN, such as the local linear or super-linear convergence rate and the local convergence guarantees for non-convex optimization problems; besides, C-ALADIN offers unique improvements in terms of communication efficiency and computational efficiency. Moreover, C-ALADIN involves a reduced version, in comparison with Consensus ADMM (Alternating Direction Method of Multipliers) [3], showing significant convergence performance, even without the help of second-order information. We also propose a practical version of C-ALADIN, named FedALADIN, that seamlessly serves the emerging federated learning applications, which expands the reach of our proposed C-ALADIN. We provide numerical experiments to demonstrate the effectiveness of C-ALADIN. The results show that C-ALADIN has significant improvements in convergence performance

The ALADIN Interactive Sky Atlas

The Aladin interactive sky atlas, developed at CDS, is a service providing simultaneous access to digitized images of the sky, astronomical catalogues, and databases. The driving motivation is to facilitate direct, visual comparison of observational data at any wavelength with images of the optical sky, and with reference catalogues. The set of available sky images consists of the STScI Digitized Sky Surveys, completed with high resolution images of crowded regions scanned at the MAMA facility in Paris. A Java WWW interface to the system is available at: http://aladin.u-strasbg.fr/Comment: 8 pages, 3 Postscript figures; to be published in A&

Enhancing collaboration and civil benefit through institutional resilience: Five principles to help achieve a longer and more prosperous exchange

Ahead of an event next week on developing collaborative research opportunities, we asked speaker Professor aladin aladin to provide his thoughts on strengthening collaborations and engaging with new partners in the university. He argues that if institutions and individuals deepen their awareness of the civil benefit to society, this will strengthen the resilience of collaborative interactions. With significant experience working across societal sectors, aladin offers five strategic planning principles relevant for institutions and individual researchers looking to achieve long-lasting and mutual beneficial partnerships

Airborne lidar observations supporting the ADM-Aeolus mission for global wind profiling

The Atmospheric Dynamics Mission ADM-Aeolus of ESA will be the first lidar mission to sense the global wind field from space. The instrument is based on a direct-detection Doppler lidar operating at 354.9 nm with two spectrometers for aerosol/cloud and molecular backscatter. In order to assess the performance of the Doppler lidar ALADIN on ADM-Aeolus and to optimize the retrieval algorithms with atmospheric signals, an airborne prototype – the ALADIN Airborne Demonstrator A2D – was developed. The A2D was the first airborne direct-detection Doppler lidar with its maiden flight on the DLR Falcon aircraft in 2005. Three airborne campaigns with a coherent-detection 2-μm wind lidar and the direct-detection wind lidar A2D were performed for pre-launch validation of Aeolus from 2007-2009. Furthermore, a unique experiment for resolving the Rayleigh-Brillouin spectral line shape in the atmosphere was accomplished in 2009 with the A2D from a mountain observatory at an altitude of 2650 m. Results of this experiment and the latest airborne campaign in the vicinity of Greenland and Iceland will be discussed

20 years of Croatian participation in ALADIN and RC LACE projects

U radu je dan kratak osvrt na povijest sudjelovanja Hrvatske u ALADIN i RC LACE projektima. Hrvatski doprinos razvoju ALADIN modela obavlja se u okviru rada RC LACE grupe, pa je posebna pažnja posvećena upravo RC LACE suradnji. Naglašen je znanstveni i stručni doprinos hrvatskih znanstvenika na pojedinim temama, učešće Hrvatske u organizaciji ALADIN I RC LACE sastanaka, radionica i seminara. Od uključenja Hrvatske u ALADIN i RC LACE projekte realizirano je 68 dugotrajnijih boravaka 19 hrvatskih meteorologa u meteorološkim službama zemalja članica. U razdoblju od uspostave ALADIN/HR operative u Hrvatskoj do kraja 2014. godine 22 hrvatska meteorologa je radilo ukupno 593 mjeseci na temama razvoja modela i razvoju i održavanju lokalnog operativnog prognostičkog ALADIN sustava. Rezultat toga je, između ostalog, znatan broj znanstvenih i stručnih radova, te doprinos mnogobrojnim domaćim i međunarodnim znanstvenim projektima.The paper gives a brief overview of the history of Croatian participation in the ALADIN and RC LACE projects. Croatian contribution to the development of the ALADIN model is carried out in the framework of RC LACE cooperation. Therefore, the special emphasis is given to the research and development activities in RC LACE group. Detailed information are given on the scientific contribution of Croatian scientists to specific topics and Croatian role in ALADIN and RC LACE management and meetings, seminar and workshops organizations. From the beginning of ALADIN and RC LACE cooperation 19 Croatian scientists realized 68 visits to consortium countries. In the period from 2000 (start of the pre-operational run in Croatia) to 2014, 22 Croatian meteorologists worked a total of 593 months on model development as well as development and maintenance of the local operational ALADIN weather prediction system. The result is, among others, a substantial number of scientific papers and contributions to numerous national and international scientific projects