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Control of Dynamically Assisted Phase-shifting Transformers
KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
2008 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, controllers for power oscillation damping, transient stability improvement and power flow control by means of a Controlled Series Compensator (CSC) and and a Dynamic Power Flow Controller (DPFC) are proposed. These devices belong to the group of power system components referred to as Flexible AC Transmission System (FACTS) devices. The developed controllers use only quantities measured locally at the FACTS device as inputs, thereby avoiding the risk of interrupted communications associated with the use of remote signals for control.

For power systems with one dominating, poorly damped inter-area power oscillation mode, it is shown that a simple generic system model can be used as a basis for damping- and power flow control design. The model for control of CSC includes two synchronous machine models representing the two grid areas participating in the oscillation and three reactance variables, representing the interconnecting transmission lines and the FACTS device. The model for control of DPFC is of the same type but it also includes the phase shift of the internal phase-shifting transformer of the DPFC.

The key parameters of the generic grid models are adaptively set during the controller operation by estimation from the step responses in the FACTS line power to the changes in the line series reactance inserted by the FACTS device. The power oscillation damping controller is based on a time-discrete, non-linear approach which aims to damp the power oscillations and set the desired power flow on the FACTS line by means of two step changes in the line reactance separated in time by half an oscillation cycle.

A verification of the proposed controllers was done by means of digital simulations using power system models of different complexities. The CSC and DPFC controllers were shown to significantly improve the small-signal- and transient stability in one four-machine system of a type commonly used to study inter-area oscillations. The CSC controller was also tested for 18 different contingencies in a 23-machine system, resulting in an improvement in both the system transient stability and the damping of the critical oscillation mode.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , x, 172 p.
Series
Trita-EE, ISSN 1653-5146 ; 2008:008
Keyword [en]
Thyristor Controlled Series Capacitor, Thyristor Switched Series Capacitor, Controlled Series Compensator, Dynamic Power Flow Controller, Phase-Shifting Transformer, Power Oscillation Damping, Transient Stability, Power Flow Control, Adaptive Control
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-4653ISBN: 978-91-7178-879-5 (print)OAI: oai:DiVA.org:kth-4653DiVA: diva2:13258
Presentation
2008-03-28, E2, Lindstedtsvägen 3, KTH, 13:00
Opponent
Supervisors
Note
QC 20101112Available from: 2008-02-27 Created: 2008-02-27 Last updated: 2010-11-12Bibliographically approved
List of papers
1. Estimation of grid parameters for the control of variable series reactance FACTS devices
Open this publication in new window or tab >>Estimation of grid parameters for the control of variable series reactance FACTS devices
2006 (English)In: 2006 POWER ENGINEERING SOCIETY GENERAL MEETING, VOLS 1-9, 2006, 105-111 p.Conference paper, Published paper (Refereed)
Abstract [en]

For high performance control of Flexible AC Transmission System (FACTS) devices with controllable reactances, a representation of the surrounding grid is essential. Using such a model, an adaptive control strategy can be developed which optimizes the control in real time as the grid parameters change. This paper proposes such a generic grid model and derives the theory of how to estimate the main parameters using measurements of the line active power response from small step reactance changes. The estimation methods are verified using simple grid models in PSCAD simulations and more advanced grid models using SIMPOW simulations of a modified version of the CIGRE Nordic 32 grid. This work should be thought of as a foundation for developing control systems for variable series reactance FACTS devices.

Series
IEEE Power Engineering Society General Meeting, ISSN 1932-5517
Keyword
parameter estimation, power system stability, power transmission control, prediction methods, FACTS
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8038 (URN)10.1109/PES.2006.1708919 (DOI)000247080000022 ()978-1-4244-0492-6 (ISBN)
Conference
General Meeting of the Power-Engineering-Society, Montreal, CANADA, JUN 18-22, 2006
Note
QC 20101112Available from: 2008-02-27 Created: 2008-02-27 Last updated: 2011-10-10Bibliographically approved
2. Discrete open loop control for power oscillation damping utilizing variable series reactance FACTS devices
Open this publication in new window or tab >>Discrete open loop control for power oscillation damping utilizing variable series reactance FACTS devices
2006 (English)In: PROCEEDINGS OF THE 41ST INTERNATIONAL UNIVERSITIES POWER ENGINEERING CONFERENCE, 2006, 785-789 p.Conference paper, Published paper (Refereed)
Abstract [en]

This paper describes an open loop method of controlling FACTS devices for power oscillation damping. The method is based on step-wise series reactance modulation. The principle of the method is to stabilize an oscillation in a power system which is characterized by one major mode of oscillation by switching a reactance in series with one transmission line, thereby changing the total reactance between the areas participating in the oscillation. In order to stabilize the system during an oscillation, the stationary voltage angle difference between the areas is changed to coincide with the present angle at a point where the speed of the lumped machine representations of the areas is nominal. This is the case at the peaks of the oscillation. To determine the required size of the reactance step, a reduced model of the power system is used. The model parameters are continuously updated using local measurements of the active power on the reactance controlled line. Several approaches for damping with different numbers of steps are presented and verified using digital simulations of power system models.

Keyword
Damping, Electric impedance, Electric power systems, Electric power transmission networks, Model structures, Modulation, Active Power (CO), angle difference, Digital simulations, FACTS (Flexible AC Transmission System) devices, In order, International (CO), Local measurements, machine representations, Model parameters, Open loop controlling, Open-loop method, power engineering, Power oscillation damping, Power system modelling, power systems, Reduced models, Transmission line (TL)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8039 (URN)10.1109/UPEC.2006.367586 (DOI)000256054900159 ()2-s2.0-46849086754 (Scopus ID)
Conference
41st International Universities Power Engineering Conference, Newcastle upon Tyne, ENGLAND, SEP 06, 2006-SEP 08, 2008
Note
QC 20101112Available from: 2008-02-27 Created: 2008-02-27 Last updated: 2011-08-19Bibliographically approved
3. An adaptive model predictive approach to power oscillation damping utilizing variable series reactance FACTS devices
Open this publication in new window or tab >>An adaptive model predictive approach to power oscillation damping utilizing variable series reactance FACTS devices
2006 (English)In: PROCEEDINGS OF THE 41ST INTERNATIONAL UNIVERSITIES POWER ENGINEERING CONFERENCE, 2006, 790-794 p.Conference paper, Published paper (Refereed)
Abstract [en]

This paper describes an adaptive method of controlling FACTS devices for power oscillation damping. The method is based on step-wise series reactance modulation. Here, a reduced model of the power system with only two rotating masses is used as a basis for the control design. The model parameters are updated using local measurements of the active power on the controlled line. An adaptive closed loop controller is developed based on the principle that it is possible to stabilize an oscillation in a power system which is characterized by one major mode of oscillation by switching a reactance in series with one transmission line in a small number of steps. The reduced model parameters are recomputed when new information of the system response is known making the control scheme an adaptive one. The paper also includes the derivation of a damping controller with a power flow control feature and a verification of the controllers using digital simulations of power system models of different complexities.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8040 (URN)10.1109/UPEC.2006.367587 (DOI)000256054900160 ()2-s2.0-46849089203 (Scopus ID)978-1-86135-342-9 (ISBN)
Conference
41st International Universities Power Engineering Conference, Newcastle upon Tyne, ENGLAND, SEP 06, 2006-SEP 08, 2008
Note
QC 20101112Available from: 2008-02-27 Created: 2008-02-27 Last updated: 2011-08-19Bibliographically approved
4. Adaptive control of controlled series compensators for power system stability improvement
Open this publication in new window or tab >>Adaptive control of controlled series compensators for power system stability improvement
2007 (English)In: 2007 IEEE LAUSANNE POWERTECH, 2007, 355-360 p.Conference paper, Published paper (Refereed)
Abstract [en]

This paper describes the design and verification of a time-discrete adaptive controller for damping of inter-area power oscillations, power flow control, and transient stability improvement Only locally measured signals are used as inputs to the controller. The controller may be used with any FACTS device which operates as a variable series reactance in the power grid, such as for example the TCSC. The controller is based on a reduced system model which relies on the assumption of one dominating inter-area oscillation mode in the power system where the FACTS device is placed. Verification of the controller is performed by means of digital simulations of a four-machine system commonly used to study inter-area oscillations.

Keyword
control, FACTS, power oscillation, TCSC, TSSC, transient stability
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8041 (URN)10.1109/PCT.2007.4538343 (DOI)000258730100062 ()2-s2.0-50849087016 (Scopus ID)978-1-4244-2189-3 (ISBN)
Conference
IEEE Lausanne Powertech, Lausanne, SWITZERLAND, JUL 01-05, 2007
Note
QC 20101112Available from: 2008-02-27 Created: 2008-02-27 Last updated: 2011-08-19Bibliographically approved
5. A dynamic power flow controller for power system stability improvement and loss reduction
Open this publication in new window or tab >>A dynamic power flow controller for power system stability improvement and loss reduction
2008 (English)In: The 16th Power Systems Computation Conference, Power Systems Computation Conference ( PSCC ) , 2008Conference paper, Published paper (Refereed)
Abstract [en]

In this paper, a novel FACTS device denoted Dynamic Power Flow Controller (DPFC) is described. The device consists of a Phase-Shifting Transformer (PST) connected in series with a set of thyristor-switched capacitive and/or inductive elements. When compared to a normal PST, this device has faster dynamic properties and in addition to the normal PST functions, it also allows for power oscillation damping, transient stability improvement, and voltage stability improvement in a power grid. The DPFC is believed to be less costly than other FACTS devices with the same functionalities. In this paper, the benefits and functions of the DPFC are discussed. Additionally, an adaptive controller for DPFC power oscillation damping, transient stability improvement, and power flow control is presented and verified by means of digital simulations.

Place, publisher, year, edition, pages
Power Systems Computation Conference ( PSCC ), 2008
Keyword
Adaptive control, Dynamic Power Flow Controller, FACTS, Phase-Shifting Transformer, Power Oscillation Damping, Transient Stability, Power Flow Control
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8042 (URN)2-s2.0-84944111649 (Scopus ID)
Conference
16th PSCC, Glasgow, Scotland, July 14-18, 2008
Note

QC 20101112

Available from: 2008-02-27 Created: 2008-02-27 Last updated: 2016-03-07Bibliographically approved

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