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Transfer capacity enhancement by adaptive coordinated controlof HVDC-links based on forecasted load paths
KTH, School of Electrical Engineering (EES), Electric Power Systems.ORCID iD: 0000-0002-2356-4795
KTH, School of Electrical Engineering (EES), Electric Power Systems.
KTH, School of Electrical Engineering (EES), Electric Power Systems.ORCID iD: 0000-0002-8189-2420
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.

Place, publisher, year, edition, pages
2011. Vol. 21, no 3, 1455-1466 p.
Keyword [en]
transfer capacity, bifurcation surface, coordinated control, HVDC, stochastic nodal loading, Monte Carlo simulation
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-30619DOI: 10.1002/etep.511ISI: 000290234100008Scopus ID: 2-s2.0-79955444469OAI: oai:DiVA.org:kth-30619DiVA: diva2:401153
Note

QC 20110302 QC 20110609

Available from: 2011-03-01 Created: 2011-03-01 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Coordinated Control of HVDC Links in Transmission Systems
Open this publication in new window or tab >>Coordinated Control of HVDC Links in Transmission 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
coordinated control, dynamic security, exact-feedback linearization, feedforward control, HVDC poser modulation
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-30625 (URN)978-91-7415-875-5 (ISBN)
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
2. A Stochastic Control Approach to Include Transfer Limits in Power System Operation
Open this publication in new window or tab >>A Stochastic Control Approach to Include Transfer Limits in Power System Operation
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The main function of the power grid is to transfer electric energy from generating facilities to consumers. To have a reliable and economical supply of electricity, large amounts of electric energy often have to be transferred over long distances.

The transmission system has a limited capacity to transfer electric power, called the transfer capacity. Severe system failures may follow if the transfer capacity is reached during operation.

Due to uncertainties, such as the random failure of system components, the transfer capacity for the near future is not readily determinable. Also, due to market principles, and reaction times and ramp rates of production facilities, power flow control is not fully flexible. Therefore, a transfer limit, which is below the transfer capacity, is decided and preventative actions are taken when the transfer reaches this limit.

In this thesis an approach to deciding an optimal strategy for power flow control through activation of regulating bids on the regulating power market is outlined. This approach leads to an optimal definition of transfer limits as the boundary between the domain where no bid should be activated and the domains where bids should be activated. The approach is based on weighing the expected cost from system failures against the production cost. This leads to a stochastic impulse control problem for a Markov process in continuous time.

The proposed method is a novel approach to decide transfer limits in power system operation. The method is tested in a case study on the IEEE 39 bus system, that shows promising results.

In addition to deciding optimal transfer limits, it is also investigated how the transfer capacity can be enhanced by controlling components in the power system to increase stability.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. xi, 67 p.
Series
Trita-EE, ISSN 1653-5146 ; 2011:070
Keyword
Frequency control, power regulating market, power system operation, power system security, stochastic impulse control, transfer capacity, transfer limit
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-41986 (URN)978-91-7501-132-5 (ISBN)
Public defence
2011-11-07, F3, Lindstedtsv 26, entréplan, KTH, S, 10:00 (English)
Opponent
Supervisors
Note
QC 20111010Available from: 2011-10-10 Created: 2011-10-04 Last updated: 2011-10-10Bibliographically approved

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