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Abstract
This thesis concerns the development of methods that can provide, in realtime,
an early warning for an emerging blackout in electric power systems.
The blackout in E-Denmark and S-Sweden on September 23, 2003 is the
main motivation for the method development. The blackout was caused by
occurrence of two severe system disturbances within a time interval of five
minutes. Following the second disturbance where initial oscillations had
damped out, a period of approximately 80s with slowly decaying voltage
magnitude was observed, before a system blackout was experienced. It was
of interest to develop methods, that could, in such situations, give an early
warning for the emerging blackout.
After investigation of data and plots taken from the time of the blackout, it
was decided to focus the development on assessment of aperiodic small signal
stability. In order to assess the system generators aperiodic small signal
stability, expressions for stability boundaries were algebraically derived in
the injection impedance plane. A method for detecting aperiodic small signal
stability was established, which was based on one of the derived boundaries.
The method carries out an element-wise assessment of the system aperiodic
small signal stability where each generator is assessed specifically by using
the value of its injection impedance and its corresponding system Thevenin
impedance.
For the purpose of obtaining distance-to-instability information, the generators
operating point were visualized in the injection impedance plane. A
mapping of the different operating points into a normalized injection impedance
plane was derived, which enabled a visualization of multiple operating
points on the same screen. Such visualization provides system operators a
new mean of graphically assessing the system conditions in respect of aperiodic
small signal stability and enables a quick identification of critical generators.
The assessment method was implemented in an algorithm, that could effectively
determine the required information for carrying out the stability assessment.
The algorithm received a PMU-snapshot of the system conditions
as an input and determined the injection and Thevenin system impedances
I
for all system generators. A test bench software was written for the purpose
of testing the developed algorithm. A large scale test of the assessment
method was carried out where a simulation of the blackout in E-Denmark
and S-Sweden September 23, 2003 was used as a test case scenario. The
simulation results were used to generate a synthetic PMU-snapshots of the
system conditions which were used as an input to the assessment algorithm.
The test results showed that the loss of aperiodic small signal stability of one
machine was detected approximately 54s before the simulated blackout was
experienced.
The developed assessment method was therefore capable of providing, in
real-time, an early warning for the occurrence of the emerging simulated
blackout almost a minute before it occurred.
Original language | English |
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Publisher | Technical University of Denmark, Department of Electrical Engineering |
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Number of pages | 232 |
ISBN (Print) | 978-87-92465-95-5 |
Publication status | Published - 2011 |
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Dive into the research topics of 'Development of Early Warning Methods for Electric Power Systems'. Together they form a unique fingerprint.Projects
- 1 Finished
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Development of PMU-based early Warning Detection System for the Electric Power System
Jóhannsson, H. (PhD Student), Nielsen, A. H. (Main Supervisor), Østergaard, J. (Supervisor), Bruun, K. E. (Examiner), Kundur, P. S. (Examiner) & Andersson, G. (Examiner)
01/04/2007 → 24/08/2011
Project: PhD