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  • 1.
    Elkington, Katherine
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Modelling and Control of Doubly Fed Induction Generators in Power Systems: Towards understanding the impact of large wind parks on power system stability2009Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The rapid development of wind power technology is reshaping conventional power grids in many countries across the world. As the installed capacity of wind power increases, its impact on power grids is becoming more important. To ensure the reliable operation of a power system which is significantly fed by wind power, the dynamics of the power system must be understood, and the purpose of this study is to develop suitable analytical tools for analysing the dynamic impact of large-scale wind parks 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.Many of the newer, larger turbines now being produced are variable speed turbines, which use doubly fed induction generators (DFIGs). These are induction generators which have their stator and rotor independently excited. When unconventional generators of this type are used in a power system, the system behaves differently under abnormal dynamic events.  For example, new types of generators cause different modes of oscillation in the power system, not only because of their dynamic characteristics, but also because they load the system differently.Very large power oscillations can occur in a power system as a result of internal disturbances.  Ordinarily these oscillations are slow and, in principle, it is possible to damp them with the help of wind power.  This leads to the idea of using a power system stabiliser (PSS) for a DFIG.  In order to damp oscillations in the system, it is necessary to understand the equipment causing these oscillations, and the methods to optimally damp the oscillations.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.  The voltage stability must therefore be carefully analysed in order to guard against a power system collapse.By using modal analysis and dynamic simulations, we show that the presence of a wind farm in the vicinity of a power system will improve the angular behaviour of the power system under small disturbances, but may decrease voltage stability under larger disturbances. We compare the performance of wind turbines to that of conventional synchronous generator power plants, and we show that a wind park consisting of DFIGs, which are equipped with PSSs, may be used as a positive contribution to power system damping.

  • 2.
    Elkington, Katherine
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    The Dynamic Impact of Large Wind Farms on Power System Stability2012Doctoral 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.

  • 3.
    Elkington, Katherine
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Wind power stabilising control: Demonstration on the Nordic grid2012Report (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.

  • 4.
    Elkington, Katherine
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Comparison of reduced order doubly fed induction generator models for nonlinear analysis2009In: 2009 IEEE Electrical Power and Energy Conference, EPEC 2009, 2009Conference paper (Refereed)
    Abstract [en]

    This article compares the behaviour of different order models, for large scale wind farms comprising doubly fed induction generators (DFIGs). While it is important to have a model which is detailed enough that all interesting phenomena can be examined, it is also important to have simple models, not only to reduce computation time, but also to simplify the design of controllers. This article compares the characteristics of different order models for DFIGs and their responses to control. Eigenvalue analysis and numerical simulations are used to compare the characteristics of the different order models.

  • 5.
    Elkington, Katherine
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Nonlinear Power Oscillation Damping Controllers for Doubly Fed Induction Generators in Wind Farms2013In: IET Renewable Power Generation, ISSN 1752-1416, E-ISSN 1752-1424, Vol. 7, no 2, p. 172-179Article in journal (Refereed)
    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.

  • 6.
    Elkington, Katherine
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Using power system stabilisers in doubly fed induction generators2008In: 2008 Australasian Universities Power Engineering Conference, AUPEC 2008, 2008Conference 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.

  • 7.
    Elkington, Katherine
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Knazkins, Valerijs
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Modal analysis of power systems with doubly fed induction generators2007In: 2007 IREP SYMPOSIUM- BULK POWER SYSTEM DYNAMICS AND CONTROL: VII REVITALIZING OPERATIONAL RELIABLITY, VOLS 1 AND 2, NEW YORK: IEEE , 2007, p. 140-147Conference 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 conventional power system. Inspection of the eigenstructure of the system provides a foundation for assessment of the impact, which is then quantified by means of detailed numerical simulations. Simplified state-space models are used to describe the dynamics of 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.

  • 8.
    Elkington, Katherine
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Knazkins, Valerijs
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    On the rotor angle stability of power systems with Doubly Fed Induction Generators2007In: 2007 IEEE LAUSANNE POWERTECH, VOLS 1-5, NEW YORK: IEEE , 2007, p. 213-218Conference 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.

  • 9.
    Elkington, Katherine
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Latorre, Hector
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Operation of Doubly Fed Induction Generators in Power Systems with VSC-HVDC Transmission2010In: AC and DC Power Transmission, 2010. ACDC, 2010, p. 1-6Conference paper (Refereed)
    Abstract [en]

    In this article we investigate the interaction of a wind park comprising doubly fed induction generators and a VSC-HVDC link in a test power system. We look at the combined impact of the components on power oscillation damping and voltage support.

  • 10.
    Elkington, Katherine
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Slootweg, J. G.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Kling, W. L.
    Reduced-Order Modelling of Wind Turbines2012In: Wind Power in Power Systems, John Wiley & Sons, 2012, 2, p. 821-847Chapter in book (Refereed)
    Abstract [en]

    In this chapter power system dynamics simulation(PSDS) isused to study the dynamics of large-scale power systems. It is necessary to incorporate models of wind turbine generating systems into PSDS software packages in order to analyse the impact of high wind power penetration on electrical power systems. These models need to match the assumptions and simplifications applied in this type of simulation. This chapter presents models that can be used to represent wind turbines in PSDSs. We give a brief introduction to PSDS, and describe the three main wind turbine types and the assumptions on which they are modelled. We then present the models of the various subsystems of each of the most important current wind turbine types are then presented. The response of the models to a simulated wind speed sequence is then shown.

  • 11.
    Hamon, Camille
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Elkington, Katherine
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Doubly-fed Induction Generator Modeling and Control in DigSilent PowerFactory2010In: 2010 International Conference on Power System Technology: Technological Innovations Making Power Grid Smarter, POWERCON2010, IEEE , 2010, p. 1-7Conference paper (Refereed)
    Abstract [en]

    Several computer programs exist to carry out dynamicsimulations and this study will focus on one of them,namely DigDilent PowerFactory. It offers two built-in modelsof doubly-fed induction generator. A new model has also beendeveloped, based upon a controllable voltage source. Thesethree models are compared, in terms of dynamic behavior andsimulation time. One of them is then used to study the impact ofan input control signal based on the single machine equivalentmethod. This signal provides power oscillation damping.

1 - 11 of 11
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  • modern-language-association-8th-edition
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