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Analysis of Centralized versus Distributed Two-stage Network Topology Processor for HVDC Grid Operation
KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.ORCID iD: 0000-0003-3946-7655
KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.ORCID iD: 0000-0003-3014-5609
(English)In: Journal of Engineering Applications of Artificial IntelligenceArticle in journal (Refereed) Submitted
Abstract [en]

This paper proposes and analyzes a two-stage network topology processorthat considers a centralized or a distributed method to identify the HVDCgrids connectivity. In the first stage of the two-stage processor, the substationtopology is analyzed locally using an automated graph-based algorithm.Thereafter, the processed information is sent to the second stage todetermine the HVDC grid connectivity and detect islands. Two possible approachesnamely, centralized and distributed methods, are formulated andstudied for this second stage. In the centralized method, k-means clusteringis used to detect islands. In the distributed method, the informationprocessed locally at the substation is exchanged between neighboring substationsto realize the grid connectivity. For distributed islanding detection,the connectivity problem is formulated as a set of linear equations and solvediteratively using successive-over-relaxation method. The performance of twoproposed methods versus conventional one-stage method has been tested inan islanding scenario for a 5-terminal HVDC grid.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-202752OAI: oai:DiVA.org:kth-202752DiVA: diva2:1078538
Note

QCR 20170306

Available from: 2017-03-05 Created: 2017-03-05 Last updated: 2017-03-06Bibliographically approved
In thesis
1. Distributed Control of HVDC Transmission Grids
Open this publication in new window or tab >>Distributed Control of HVDC Transmission Grids
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Recent issues such as priority access of renewable resources recommended by European energy directives and increase the electricity trading among countries lead to new requirements on the operation and expansion of transmission grids. Since AC grid expansions are limited by legislative issues and long distance transmission capacity, there is a considerable attention drawn to application of HVDC transmission grids on top of, or in complement to, existing AC power systems. The secure operation of HVDC grids requires a hierarchical control system. In HVDC grids, the primary control action to deal with power or DC voltage deviations is communication-free and local. In addition to primary control, the higher supervisory control actions are needed to guarantee the optimal operation of HVDC grids. However, the implementation of supervisory control functions is linked to the arrangement of system operators; i.e. an individual HVDC operator (central structure) or sharing tasks among AC system operators (distributed structure).

This thesis presents distributed control of an HVDC grid. To this end, three possible supervisory functions are investigated; coordination of power injection set-points, DC slack bus selection and network topology identification. In this thesis, all three functions are first studied for the central structure. For the distributed solution, two algorithms based on Alternating Direction Method of Multipliers (ADMM) and Auxiliary Problem Principle (APP) are adopted to solve the coordination of power injection. For distributed selection of DC slack bus, the choice of parameters for quantitative ranking of converters is important. These parameters should be calculated based on local measurements if distributed decision is desired. To this end, the short circuit capacity of connected AC grid and power margin of converters are considered. To estimate the short circuit capacity as one of the required selection parameters, the result shows that the recursive least square algorithm can be very efficiently used. Besides, it is possible to intelligently use a naturally occurring droop response in HVDC grids as a local measurement for this estimation algorithm. Regarding the network topology, a two-stage distributed algorithm is introduced to use the abstract information about the neighbouring substation topology to determine the grid connectivity.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. 51 p.
Series
TRITA-EE, ISSN 1653-5146 ; 2017:018
Keyword
co-simulation, cyber-physical system, DC slack bus, distributed control, HVDC grids, power injection, topology processor, wind farms
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-202753 (URN)978-91-7729-310-1 (ISBN)
Public defence
2017-04-10, F3, Lindstedtsvägen 26 - KTH campus, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20170306

Available from: 2017-03-06 Created: 2017-03-05 Last updated: 2017-03-10Bibliographically approved

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