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Distributed Security-Constrained Secondary Control of HVDC grids in the Presence of Wind Uncertainty
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: Sustainable Energy, Grids and Networks, ISSN 0284-4354, E-ISSN 2352-4677Article in journal (Refereed) Submitted
Abstract [en]

This paper proposes a distributed coordination of converters in an HVDC grid in order to provide close-to-real-time optimal DCvoltage and power profiles in the presence of wind uncertainty. This coordination is a part of HVDC grid secondary control actionthat carries out after the automatic primary control response by DC voltage droop controlling converters. It aims to optimize thegrid operation by finding the new DC power and voltage set-points that minimize the operational costs due to wind fluctuations andprediction error. Furthermore, the N-1 secure operation of HVDC grid is considered in this distributed coordination by adding a setof security constraints that tightens the upper and lower bounds of the problem variables. The coordination problem is formulatedas a convex optimization problem and therefore a modified version of alternating direction method of multipliers is adopted to solvethe problem in distributed manner. The performance of distributed coordination has been tested by a set of scenarios. The resultsimply that the distributed coordination is eligible in terms of time and complexity to be considered as either the main option forsecondary coordination or a complementary back-up solution for the central coordination.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-202751OAI: oai:DiVA.org:kth-202751DiVA: diva2:1078537
Note

QCR 20170306

Available from: 2017-03-05 Created: 2017-03-05 Last updated: 2017-11-29Bibliographically 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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Nordström, Lars

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