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The Dynamic Impact of Large Wind Farms on Power System Stability
KTH, School of Electrical Engineering (EES), Electric Power Systems.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

As the installed capacity of wind power increases across the world, its impact on power systems is becoming more important. To ensure the reliable operation of a power system which is significantly fed by wind power, the dynamics of the system must be understood. The purpose of this study is to analyse the dynamic impact of large-scale wind farms on the stability of a power grid, and to investigate the possibility of improving the stabilisation and damping of the grid by smart control strategies for wind turbines.

When unconventional types of generators are used in a power system, the system behaves differently under abnormal dynamic events. For example, new types of generators such as doubly fed induction generators (DFIGs) cause different modes of oscillation in the system. In order to damp oscillations in the system, it is necessary to understand the equipment causing these oscillations, and the methods of optimally damping the oscillations.

Large power oscillations can occur in a power system as a result of disturbances. Ordinarily these oscillations are slow and, in principle, it is possible to damp them with the help of wind power. This suggests the use of a power oscillation damping (POD) controller for a DFIG, similar to a power system stabiliser (PSS) for a synchronous generator. To demonstrate this concept, we design PODs for DFIGs in a wind farm.

Voltage stability is another important aspect of the safe operation of a power system. It has been shown that the voltage stability of a power system is affected by induction generators and also DFIGs. The voltage stability must therefore also be analysed in order to guard against a power system collapse.

In this study we develop models and control strategies for large wind farms comprising DFIGs, and study the impact of the wind farms on power systems. The design of multiple PODs in a wind farm is performed using linear matrix inequalities (LMIs), and the impact of the wind turbines is investigated through the use of linear and dynamic simulations. It has been demonstrated that DFIGs can be used for damping oscillations, and that they can also improve the critical clearing time of some faults. However, they may have an adverse impact on power systems after large voltage disturbances.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , viii, 63 p.
Series
Trita-EE, ISSN 1653-5146 ; 2012:016
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-93220ISBN: 978-91-7501-316-9 (print)OAI: oai:DiVA.org:kth-93220DiVA: diva2:516618
Public defence
2012-05-03, sal H1, Teknikringen 33, KTH, Stockholm, 10:30 (English)
Opponent
Supervisors
Note
QC 20120419Available from: 2012-04-19 Created: 2012-04-12 Last updated: 2012-04-19Bibliographically approved
List of papers
1. On the rotor angle stability of power systems with Doubly Fed Induction Generators
Open this publication in new window or tab >>On the rotor angle stability of power systems with Doubly Fed Induction Generators
2007 (English)In: 2007 IEEE LAUSANNE POWERTECH, VOLS 1-5, NEW YORK: IEEE , 2007, 213-218 p.Conference paper, Published paper (Refereed)
Abstract [en]

This article is concerned with the impact of large scale wind farms utilising doubly fed induction generators on the stability of a traditional thermal power system. Inspection of the eigenstructure of the power system provides a foundation for assessment of the impact, which is then quantifted by means of detailed numerical simulations. Simplified state-space models are used to describe the dynamics of the generators in a very simple system., whose network is described by algebraic relations. A third order model is derived for a doubly fed induction generator. Mathematical models are used to identify the behavioural patterns of the system when it is subject to disturbances. Eigenvalue analysis reveals certain interesting properties of the system when it is subject to small disturbances. Numerical simulations show that the addition to a power system of doubly fed induction generators, such as those found in wind farms, improves the response of the system to small disturbances, but can have an adverse impact after larger disturbances.

Place, publisher, year, edition, pages
NEW YORK: IEEE, 2007
Keyword
DFIG, doubly fed induction generator, stability, power system, one-axis model, third order, eigenvalues
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-36828 (URN)10.1109/PCT.2007.4538319 (DOI)000258730100038 ()2-s2.0-50849101958 (Scopus ID)
Conference
IEEE Lausanne Powertech Lausanne, SWITZERLAND, JUL 01-05, 2007
Note
QC 20110718Available from: 2011-07-18 Created: 2011-07-15 Last updated: 2012-04-19Bibliographically approved
2. Using power system stabilisers in doubly fed induction generators
Open this publication in new window or tab >>Using power system stabilisers in doubly fed induction generators
2008 (English)In: 2008 Australasian Universities Power Engineering Conference, AUPEC 2008, 2008Conference paper, Published paper (Refereed)
Abstract [en]

This article deals with the design and usage of a power system stabiliser (PSS) and its impact in the controller of a doubly fed induction generator (DFIG). Eigenvalue analysis and numerical simulations are used to design and tune the PSS for different types of input signals, and the suitability of the signals is assessed. The impact of large scale wind farms utilising DFIGs on the oscillations of a conventional power system is compared to the impact of conventional generators in a test power system. The dynamics of a wind farm can be represented by a third order DFIG model and a simple controller model. Modal analysis and dynamic simulations are used to demonstrate the contribution made by the wind farm to power system damping. Numerical simulations show that DFIGs, such as those found in wind farms, are capable of damping oscillations.

Keyword
Controller models, Conventional power, Damping oscillation, Doubly fed induction generators, Doubly-fed induction generator, Dynamic simulation, Eigenvalue analysis, Input signal, Numerical simulation, Power system damping, Power system stabiliser, Power systems, Test power, Third order, Wind farm, Asynchronous generators, Damping, Dynamic analysis, Eigenvalues and eigenfunctions, Electric fault currents, Electric power transmission networks, Electric utilities, Farms, Modal analysis, Power transmission, Wind power, Simulators
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-36379 (URN)2-s2.0-67649663859 (Scopus ID)9781424441624 (ISBN)
Conference
2008 Australasian Universities Power Engineering Conference, AUPEC 2008; Sydney, NSW; Australia; 14 December 2008 through 17 December 2008
Note

QC 20110712

Available from: 2011-07-12 Created: 2011-07-12 Last updated: 2014-10-24Bibliographically approved
3. Nonlinear Power Oscillation Damping Controllers for Doubly Fed Induction Generators in Wind Farms
Open this publication in new window or tab >>Nonlinear Power Oscillation Damping Controllers for Doubly Fed Induction Generators in Wind Farms
2013 (English)In: IET Renewable Power Generation, ISSN 1752-1416, E-ISSN 1752-1424, Vol. 7, no 2, 172-179 p.Article in journal (Refereed) Published
Abstract [en]

This study presents two methods for designing power oscillation damping (POD) controllers for wind farms comprising doubly fed induction generators (DFIGs). The first is the residue method, which uses linear feedback. The second method uses a non-linear signal as feedback. Here linear matrix inequalities (LMIs) and regional pole placement are used to determine the feedback gains for multiple wind farms simultaneously so that the power system satisfies a minimum damping ratio. The impact of the designed POD controllers in wind farms is demonstrated in a test power system. Modal analysis is used to design controllers using both the residue and LMI methods, and dynamic simulations are used to demonstrate the contribution of the wind farms to power system damping. Numerical simulations show that DFIGs, such as those found in wind farms, are capable of damping oscillations, and also illustrate the effectiveness of using non-linear feedback controllers.

Place, publisher, year, edition, pages
Institution of Engineering and Technology, 2013
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-93221 (URN)10.1049/iet-rpg.2011.0145 (DOI)000321713300008 ()2-s2.0-84879372336 (Scopus ID)
Note

Updated from "Submitted" to "Published". QC 20160602

Available from: 2012-04-18 Created: 2012-04-12 Last updated: 2017-12-07Bibliographically approved
4. Wind power stabilising control: Demonstration on the Nordic grid
Open this publication in new window or tab >>Wind power stabilising control: Demonstration on the Nordic grid
2012 (English)Report (Other academic)
Abstract [en]

When unconventional types of generators such as doubly fed induction generators (DFIGs) are used in a power system, the system behaves differently under abnormal dynamic events. For example, DFIGs cause different modes of oscillation in the power system, and respond differently to changes in voltage. In order to damp oscillations in the system, it is necessary to understand the equipment causing these oscillations, and the methods of optimally damping the oscillations.

Large power oscillations can occur in a power system as a result of disturbances. Ordinarily these oscillations are slow and, in principle, it is possible to damp them with the help of wind power. This suggests the use of a power oscillation damping (POD) controller for a DFIG, similar to a power system stabiliser (PSS) for a synchronous generator.

Voltage stability is another important aspect of the safe operation of a power system. It has been shown that the voltage stability of a power system is affected by induction generators and also DFIGs, and we investigate some aspects of this here.

In this study we develop control strategies for large wind farms comprising DFIGs, and study the impact of the wind farms on a system which is designed to reflect the dynamics of the Nordic power system. The design of multiple PODs in a wind farm is undertaken using linear matrix inequalities (LMIs). The impact of the wind turbines is investigated through the use of linear and dynamic simulations. It has been demonstrated that DFIG-based wind farms can be used for damping oscillations, even when they are not producing their rated power, and that they can also improve the critical clearing time of some faults. However, they may have an adverse impact on power systems after large voltage disturbances.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. iv, 19 p.
Series
Trita-EE, ISSN 1653-5146 ; 2012:015
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-92302 (URN)
Note
QC 20120402Available from: 2012-04-02 Created: 2012-04-01 Last updated: 2012-04-19Bibliographically approved

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More languages
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