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Distributed Control of HVDC Transmission Grids
KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.ORCID-id: 0000-0003-3946-7655
2017 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
KTH Royal Institute of Technology, 2017. , s. 51
Serie
TRITA-EE, ISSN 1653-5146 ; 2017:018
Emneord [en]
co-simulation, cyber-physical system, DC slack bus, distributed control, HVDC grids, power injection, topology processor, wind farms
HSV kategori
Forskningsprogram
Elektro- och systemteknik
Identifikatorer
URN: urn:nbn:se:kth:diva-202753ISBN: 978-91-7729-310-1 (tryckt)OAI: oai:DiVA.org:kth-202753DiVA, id: diva2:1078539
Disputas
2017-04-10, F3, Lindstedtsvägen 26 - KTH campus, Stockholm, 10:00 (engelsk)
Opponent
Veileder
Merknad

QC 20170306

Tilgjengelig fra: 2017-03-06 Laget: 2017-03-05 Sist oppdatert: 2017-03-10bibliografisk kontrollert
Delarbeid
1. Study of Centralized and Distributed Coordination of Power Injection in Multi-TSO HVDC Grid with Large Off-shore Wind Integration
Åpne denne publikasjonen i ny fane eller vindu >>Study of Centralized and Distributed Coordination of Power Injection in Multi-TSO HVDC Grid with Large Off-shore Wind Integration
2016 (engelsk)Inngår i: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 136, s. 281-288Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This paper studies centralized and distributed schemes for the coordinationof power injection in an HVDC grid connected to large wind generation.This coordination of power injection aims to keep the power balanced withinthe HVDC grid especially during large wind disturbances. Furthermore, thecoordination tries to follow the converters’ schedules set by the connectingAC-TSOs every 15−minutes. This schedule comes from an overall combinedAC/DC economic dispatch calculation with lower resolution compared to thiscoordination. In this paper, the coordination of power injection has been formulatedas a non-linear constrained optimization problem for the centralizedarchitecture. Next, the centralized optimization problem is decomposed tosub-problems using the Auxiliary Problem Principle (APP) method for thedistributed architecture. This distributed optimization problem is solved byexchanging the required information between the AC TSOs. These two differentapproaches have been evaluated for a 5-terminal HVDC grid. Furthermore,a sensitivity analysis has been carried out to find the optimal updatingrate of power injection set-points. The result shows that the more frequentupdating of power injection coordination in the centralized architecture improvesthe generation reserves in each AC area.

sted, utgiver, år, opplag, sider
Elsevier, 2016
Emneord
Distributed optimization, HVDC grid, Optimal power injection, Wind farm
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-178726 (URN)10.1016/j.epsr.2016.03.001 (DOI)000375505800028 ()2-s2.0-84960905190 (Scopus ID)
Merknad

QC 20160413

Tilgjengelig fra: 2015-12-08 Laget: 2015-12-08 Sist oppdatert: 2017-12-01bibliografisk kontrollert
2. Selection of DC Voltage Controlling Station in an HVDC Grid
Åpne denne publikasjonen i ny fane eller vindu >>Selection of DC Voltage Controlling Station in an HVDC Grid
Vise andre…
2016 (engelsk)Inngår i: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 144, s. 224-232Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This paper proposes a real-time quantitative evaluation of HVDC converters’ in an HVDC grid to select the suitable DC slack converter. This real-time evaluation considers the strength of connecting AC grid and the converter's on-line capacity margin as selection metrics. The strength of AC grid is evaluated in real-time by the estimation of grid short circuit capacity using recursive lease square algorithm. Given these selection metrics, the credibility of HVDC stations in controlling the DC voltage can be offered to the system operator in real-time for further operational decisions. This paper also studies the practical aspect of the estimation algorithm regarding selection of the operating points. As major contribution, it suggests to intelligently use a naturally occurring droop response in HVDC grids as a second operating point in the estimation algorithm to calculate the short circuit capacity. The method has been tested through set of scenarios using a real-time co-simulation platform. This platform includes real-time power system simulator to model AC/DC grid, industrial HVDC controllers and corresponding ICT systems. The results show that the proper selection of DC slack station can improve the AC system response and DC voltage drops during disturbances.

sted, utgiver, år, opplag, sider
Elsevier, 2016
Emneord
HVDC grid, Short circuit capacity, Slack bus selection, Voltage control
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-180715 (URN)10.1016/j.epsr.2016.12.008 (DOI)000392889700024 ()2-s2.0-85006978465 (Scopus ID)
Forskningsfinansiär
SweGRIDS - Swedish Centre for Smart Grids and Energy Storage
Merknad

QC 20160901

Tilgjengelig fra: 2016-01-21 Laget: 2016-01-21 Sist oppdatert: 2017-11-30bibliografisk kontrollert
3. Real-Time Estimation of AC-Grid Short Circuit Capacity for HVDC Control Application
Åpne denne publikasjonen i ny fane eller vindu >>Real-Time Estimation of AC-Grid Short Circuit Capacity for HVDC Control Application
Vise andre…
2016 (engelsk)Inngår i: IET Generation, Transmission & Distribution, ISSN 1751-8687, E-ISSN 1751-8695Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
IET, 2016
Emneord
estimation, HVDC, real-time, recursive least square, short circuit capacity
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-180714 (URN)10.1049/iet-gtd.2016.0465 (DOI)
Forskningsfinansiär
SweGRIDS - Swedish Centre for Smart Grids and Energy Storage
Merknad

QC 20160901

Tilgjengelig fra: 2016-01-21 Laget: 2016-01-21 Sist oppdatert: 2017-11-30bibliografisk kontrollert
4. Distributed Security-Constrained Secondary Control of HVDC grids in the Presence of Wind Uncertainty
Åpne denne publikasjonen i ny fane eller vindu >>Distributed Security-Constrained Secondary Control of HVDC grids in the Presence of Wind Uncertainty
(engelsk)Inngår i: Sustainable Energy, Grids and Networks, ISSN 0284-4354, E-ISSN 2352-4677Artikkel i tidsskrift (Fagfellevurdert) 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.

HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-202751 (URN)
Merknad

QCR 20170306

Tilgjengelig fra: 2017-03-05 Laget: 2017-03-05 Sist oppdatert: 2017-11-29bibliografisk kontrollert
5. Distributed Two-stage Network Topology Processor for HVDC Grid Operation
Åpne denne publikasjonen i ny fane eller vindu >>Distributed Two-stage Network Topology Processor for HVDC Grid Operation
2017 (engelsk)Inngår i: 2017 IEEE Manchester PowerTech, Powertech 2017, IEEE, 2017, artikkel-id 7980841Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

This paper presents the results of an analysis of distributed two-stage coordination of network topology processor for HVDC grids. In the first stage of the two-stage processor, the substation topology is analyzed locally using an automated graph-based algorithm. Thereafter, a distributed algorithm is proposed to used the neighboring information to realize the grid connectivity. For distributed islanding detection, the connectivity problem is formulated as a set of linear equations and solved iteratively using successive-over-relaxation method. The performance of the proposed methods versus conventional one-stage method has been tested in an islanding scenario for a 5-terminal HVDC grid.

sted, utgiver, år, opplag, sider
IEEE, 2017
Emneord
distributed coordination, HVDC grid, topology processor
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-202752 (URN)10.1109/PTC.2017.7980841 (DOI)000411142500054 ()2-s2.0-85034774933 (Scopus ID)9781509042371 (ISBN)
Konferanse
12th IEEE PES PowerTech Conference, Towards and Beyond Sustainable Energy Systems, juni 18-22, Manchester, UK
Forskningsfinansiär
SweGRIDS - Swedish Centre for Smart Grids and Energy Storage
Merknad

QC 20170627

Tilgjengelig fra: 2017-03-05 Laget: 2017-03-05 Sist oppdatert: 2018-02-26bibliografisk kontrollert
6. Implementation of agent-based power flow coordination in AC/DC grids using co-simulation platform
Åpne denne publikasjonen i ny fane eller vindu >>Implementation of agent-based power flow coordination in AC/DC grids using co-simulation platform
Vise andre…
2014 (engelsk)Inngår i: 2014 IEEE International Conference on Smart Grid Communications, SmartGridComm 2014, 2014, s. 188-193Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

This paper presents work on the coordination of power sharing contribution of converters in an overlaid HVDC grid using a Multi-Agent System (MAS) approach. This approach is further implemented in a real-time co-simulation platform in order to study the proposed control scheme including the supporting information and communication Technology (ICT) systems. The platform consists of OPNET, a communication network simulator, connected to a real-time power system simulator through virtualized and real devices. Furthermore, the impact of different supporting system parameters such as bit-error rate has been studied using this real-time co-simulation platform.

Emneord
Co-Simulation, DMU, Graph Theory, HVDC grid, Multi-Agent System, PSMIX-P
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-138036 (URN)10.1109/SmartGridComm.2014.7007644 (DOI)2-s2.0-84922422813 (Scopus ID)9781479949342 (ISBN)
Konferanse
2014 IEEE International Conference on Smart Grid Communications, SmartGridComm 2014; Venice; Italy; 3 November 2014 through 6 November 2014
Forskningsfinansiär
StandUp
Merknad

QC 20150601

Tilgjengelig fra: 2013-12-17 Laget: 2013-12-17 Sist oppdatert: 2017-03-05bibliografisk kontrollert

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