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Real-Time Estimation of AC-Grid Short Circuit Capacity for HVDC Control Application
KTH, School of Electrical Engineering (EES), Electric power and energy systems.ORCID iD: 0000-0003-3946-7655
KTH, School of Electrical Engineering (EES).
HVDC, ABB Sweden, Ludvika.
HVDC, ABB Sweden, Ludvika.
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2016 (English)In: IET Generation, Transmission & Distribution, ISSN 1751-8687, E-ISSN 1751-8695Article in journal (Refereed) Published
Abstract [en]

Being able to estimate the AC grid strength using Short Circuit Capacity (SCC) fromthe perspective of a connected HVDC station allows adjustment of converter control parameters orto select the converter’s operational control mode. The short circuit capacity can be calculated byestimation of the grid’s impedance and its equivalent voltage. This paper presents the operationaland practical challenges in real-time implementation of the grid estimation algorithms especiallyfor HVDC applications. This paper shows that the Recursive Least Square (RLS) algorithm can bevery efficiently used for the real-time estimation of SCC. This technique forms a regression prob-lem using algebraic complex equations with an objective to minimize the error between estimatedand measured parameters. The algorithm has been reformulated and simplified to make it non-complex without the use of matrices, in order to facilitate further implementation on an industrialreal-time controller. The performance of the real-time implementation has been evaluated usinga HIL platform. A sensitivity analysis has been also carriedout to study the impact of differentparameters and operational conditions on the performance of the estimation algorithm. Finally, theactual application of real-time SCC estimation for the HVDCsystems has been demonstrated.

Place, publisher, year, edition, pages
IET , 2016.
Keyword [en]
estimation, HVDC, real-time, recursive least square, short circuit capacity
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-180714DOI: 10.1049/iet-gtd.2016.0465OAI: oai:DiVA.org:kth-180714DiVA: diva2:896373
Funder
SweGRIDS - Swedish Centre for Smart Grids and Energy Storage
Note

QC 20160901

Available from: 2016-01-21 Created: 2016-01-21 Last updated: 2017-03-05Bibliographically 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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