Change search
ReferencesLink to record
Permanent link

Direct link
Coordinated Control of HVDC Links in Transmission Systems
KTH, School of Electrical Engineering (EES), Electric Power Systems.
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Dynamic security limits the power transfer capacity between regions and therefore has an economic impact. The power modulation control of high-voltage direct current (HVDC) links can improve the dynamic security of the power system. Having several HVDC links in a system creates the opportunity to coordinate such control, and coordination also ensures that negative interactions do not occur among the controllable devices.

This thesis aims to increase dynamic security by coordinating HVDC links, as an alternative to decreasing the transfer capacity. This thesis contributes four control approaches for increasing the dynamic stability, based on feedforward control, adaptive control, optimal control, and exact-feedback linearization control. Depending on the available measurements, dynamic system model, and system topology, one of the developed methods can be applied. The wide-area measurement system provides the central controller with real-time data and sends control signals to the HVDC links.

The feedforward controller applies rapid power dispatch, and the strategy used here is to link the N-1 criterion between two systems. The adaptive controller uses the modal analysis approach; based on forecasted load paths, the controller gains are adaptively adjusted to maximize the damping in the system. The optimal controller is designed based on an estimated reduced-order model; system identification develops the model based on the system response. The exact-feedback linearization approach uses a pre-feedback loop to cancel the nonlinearities; a stabilizing controller is designed for the remaining linear system.

The conclusion is that coordinating the HVDC links improves the dynamic stability, which makes it possible to increase the transfer capacity. This conclusion is also supported by simulations of each control approach.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , x, 51 p.
Series
Trita-EE, ISSN 1653-5146 ; 2011:004
Keyword [en]
coordinated control, dynamic security, exact-feedback linearization, feedforward control, HVDC poser modulation
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-30625ISBN: 978-91-7415-875-5OAI: oai:DiVA.org:kth-30625DiVA: diva2:401164
Public defence
2011-03-24, Sal K2, Teknikringen 28, Entréplan, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20110302Available from: 2011-03-02 Created: 2011-03-01 Last updated: 2011-03-02Bibliographically approved
List of papers
1. Coordination of multiple power flow controlling devices in transmission systems
Open this publication in new window or tab >>Coordination of multiple power flow controlling devices in transmission systems
2010 (English)In: ACDC 2010: 9th International Conference on AC and DC Power Transmission, 2010Conference paper (Refereed)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-30621 (URN)
Conference
9th International Conference on AC and DC Power Transmission, London 2010
Note
QC 20110302Available from: 2011-03-01 Created: 2011-03-01 Last updated: 2011-03-02Bibliographically approved
2. Transfer capacity enhancement by adaptive coordinated controlof HVDC-links based on forecasted load paths
Open this publication in new window or tab >>Transfer capacity enhancement by adaptive coordinated controlof HVDC-links based on forecasted load paths
2011 (English)In: European transactions on electrical power, ISSN 1430-144X, E-ISSN 1546-3109, Vol. 21, no 3, 1455-1466 p.Article in journal (Refereed) Published
Abstract [en]

Due to the intensive use of the transmission networks one of the major issues in electric energy trading is bottlenecks limiting the transfer capacity between different system areas. In this article, a new method for increasing transfer capacity is suggested. The increase in transfer capacity is obtained by an adaptive coordinated modulation control of multiple HVDC-links in the system. The control method is based on maximizing the distance to the bifurcation surface by adjusting the feedback gain of the HVDC-links modulation controllers. The system is linearized along the forecasted load path. The feedback gains are then chosen in such a way that system remains stable, in a small signal sense, as long as possible along the forecasted load path. The arising optimization problem is then solved using a particle swarm optimization method. If the load is predicted to increase, instability will eventually occur when the loading reaches a critical limit. Using the proposed control method the point in load-space where instability occur will be at a significantly higher loading level. The main contribution of this paper is the proposed new method for adaptively coordinating the power modulation of multiple HVDC-links in a power system, to enhance the total transfer capacity. This in turn will lead to a possibility to increase the traded volumes on the electricity market.

Keyword
transfer capacity, bifurcation surface, coordinated control, HVDC, stochastic nodal loading, Monte Carlo simulation
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-30619 (URN)10.1002/etep.511 (DOI)000290234100008 ()2-s2.0-79955444469 (ScopusID)
Note

QC 20110302 QC 20110609

Available from: 2011-03-01 Created: 2011-03-01 Last updated: 2014-01-22Bibliographically approved
3. Coordinated control design of multiple HVDC links based on model identification
Open this publication in new window or tab >>Coordinated control design of multiple HVDC links based on model identification
2010 (English)In: Computers and Mathematics with Applications, ISSN 0898-1221, Vol. 60, no 4, 944-953 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a method for designing a centralized coordinated controller for several HVDC links. The controller increases the damping of the power oscillations by modulating the current through the HVDC links in a coordinated fashion. To design a centralized coordinated controller a reduced order open system model is estimated. The open system model of the power system is estimated using the Numerical Algorithms for Subspace State-Space System Identification (N4SID) algorithm which is a black-box system identification technique. The current set-point change through the HVDC links is the set of input signals and the speeds of the generators are the set of outputs. This controller design method increases the damping significantly, which is shown for a small power system.

Keyword
Coordinated control, HVDC link, Modal analysis, Small signal stability, System identification
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-29234 (URN)10.1016/j.camwa.2010.02.037 (DOI)000281175200003 ()2-s2.0-77955428022 (ScopusID)
Note
QC 20110128Available from: 2011-01-28 Created: 2011-01-27 Last updated: 2011-03-02Bibliographically approved
4. Wide-Area measurement system-based subspace identification for obtaining linear models to centrally coordinate controllable devices
Open this publication in new window or tab >>Wide-Area measurement system-based subspace identification for obtaining linear models to centrally coordinate controllable devices
2011 (English)In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 0885-8877, Vol. 26, no 2, 988-997 p.Article in journal (Refereed) Published
Abstract [en]

The contribution of this paper is the application of subspace system identification techniques, to derive a low-order black-box state-space model of a power system with many controllable devices using global signals. This model is a multiinput, multioutput open system model describing the power oscillatory behavior of the power system. The input signals are the controllable setpoints of the controllable devices, the output signals are the speed of selected generators measured by a wide-area measurement system. This paper describes how to achieve and preprocess the data to use subspace techniques to estimate and validate to finally assign an accurate model. This new approach can be used directly to design a central coordinating controller for all of the relevant controllable devices, with the aim to increase the damping of the modes in the system. Previously presented methods use local measurements or output signals dependent on the actual operational point. The benefit of the presented method is that the used output signals are independent of the system state. This makes it possible to use state-feedback control to combine the controllable devices to coordinately damp the modes. The presented method is applied in the CIGRÉ Nordic 32-bus system including two HVDC links. The case study demonstrates that accurate low-order state-space models can be estimated and validated by using the described method to accurately model the system's power oscillatory behavior.

Keyword
Flexible ac transmission system (FACTS) devices, Generators, HVDC, HVDC transmission, N4SID, Noise, Oscillators, Power system dynamics, Power system stability
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-30623 (URN)10.1109/TPWRD.2010.2094628 (DOI)000288758400054 ()2-s2.0-79953200099 (ScopusID)
Note
QC 20110302Available from: 2011-03-01 Created: 2011-03-01 Last updated: 2012-01-11Bibliographically approved
5. Optimal coordinated control of multiple HVDC links for power oscillation damping based on model identification
Open this publication in new window or tab >>Optimal coordinated control of multiple HVDC links for power oscillation damping based on model identification
2012 (English)In: European transactions on electrical power, ISSN 1430-144X, E-ISSN 1546-3109, Vol. 22, no 2, 188-205 p.Article in journal (Refereed) Published
Abstract [en]

This paper deals with optimal coordinated control of several high voltage direct current (HVDC) links based on an estimated model of large power systems. The model of the power system is estimated by using subspace system identification techniques. An optimal controller is designed based on the estimated model with the aim to improve the damping in the system. The main contribution of this paper is the development of a new method which uses global Phasor measurement units (PMUs) signals for coordinated damping control of multiple HVDC links. The input signals are the controllable set-points of the HVDC links, the output signals are the speed signals of selected generators obtained from PMU. The PMU signals are used to estimate the current state of the model, i.e., the state of the system, an appropriate control action can then be applied to dampen the system. The benefit of the method is that the used output signals, i.e., the used PMU signals, are independent of the system equilibrium and therefore makes it possible to use state-feedback control, i.e., coordinated control. The method is applied to the Cigre Nordic 32-bus system including two HVDC links. The consistent results show that the damping can be significantly increased.

Keyword
HVDC, inter-area oscillations, modal analysis, N4SID, Nordic 32-bus system, PMU, optimal control, small signal analysis, subspace system identification, WAMS
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-30624 (URN)10.1002/etep.554 (DOI)000302015200006 ()2-s2.0-84859025613 (ScopusID)
Funder
StandUp
Note

QC 20120503

Available from: 2011-03-01 Created: 2011-03-01 Last updated: 2013-04-16Bibliographically approved
6. Coordinated control of multiple HVDC links using input-output exact linearization
Open this publication in new window or tab >>Coordinated control of multiple HVDC links using input-output exact linearization
2010 (English)In: Electric power systems research, ISSN 0378-7796, Vol. 80, no 12, 1406-1412 p.Article in journal (Refereed) Published
Abstract [en]

This paper is concerned with the investigation of a new control technique for the conventional High Voltage Direct Current (HVDC) link. The proposed technique relies upon nonlinear state feedback linearization of the AC/DC power system. The idea in input-output exact feedback linearization is to algebraically transform nonlinear systems dynamics into a linear control problem using a nonlinear pre-feedback loop, and then for the linearized power system one can design another feedback loop using a well established technique such as a linear-quadratic regulator. The primary goal of the controller presented in this paper is to contribute to the enhancement of both the transient and the small-signal stability of the power system. Since the proposed state feedback linearization does not rely on the assumption that there is only small deviation of the states from an equilibrium, the enhancement of both is feasible. The simulation results obtained in the framework of the study show that the proposed controller is capable of stabilizing the system in various system operating conditions.

Keyword
Nonlinear control, Coordinated control, High Voltage Direct Current (HVDC), Power system stability, Feedback linearization
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-26646 (URN)10.1016/j.epsr.2010.06.001 (DOI)000282404500003 ()2-s2.0-77956339406 (ScopusID)
Note
QC 20101203Available from: 2010-12-03 Created: 2010-11-26 Last updated: 2011-03-02Bibliographically approved
7. A general approach to coordinated control of multiple HVDC links using input-output exact linearization
Open this publication in new window or tab >>A general approach to coordinated control of multiple HVDC links using input-output exact linearization
(English)Article in journal (Other academic) Submitted
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-30639 (URN)
Note
QS 20120326Available from: 2011-03-02 Created: 2011-03-02 Last updated: 2012-03-26Bibliographically approved

Open Access in DiVA

fulltext(402 kB)2573 downloads
File information
File name FULLTEXT01.pdfFile size 402 kBChecksum SHA-512
bd2e09e0e9bf303962b3eb2887d211604c6b8b7c61df9094b62bc55a0f9ca6f6f2dfdb6a8de6807eb09edfa878f1d4282053b578c02238c92df54a34e7ee753f
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Eriksson, Robert
By organisation
Electric Power Systems
Other Electrical Engineering, Electronic Engineering, Information Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 2573 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 8399 hits
ReferencesLink to record
Permanent link

Direct link