Advanced

Power System Damping - Structural Aspects of Controlling Active Power

Samuelsson, Olof LU (1997)
Abstract (Swedish)
Popular Abstract in Swedish

Ekonomiska och miljömässiga problem gör det svårt att bygga ut kraftledningsnätet i samma takt som efterfrågan på elenergi ökar. Ett alternativ är att öka belastningen av befintliga kraftledningar på bekostnad av de säkerhetsmarginaler som finns. En av flera dimensionerande faktorer är risken för otillräckligt dämpade effektpendlingar mellan generatorer i kraftsystemet. Avhandlingen föreslår dämpning av effektpendlingar genom styrning av elpannor eller andra elektriska belastningar som huvudsakligen drar aktiv effekt. Detta demonstrerades vid ett fältförsök där pendlingar mellan ett mindre vattenkraftverk på 900 kW och övriga kraftsystemet dämpades genom att styra fyra värmefläktar på vardera 5... (More)
Popular Abstract in Swedish

Ekonomiska och miljömässiga problem gör det svårt att bygga ut kraftledningsnätet i samma takt som efterfrågan på elenergi ökar. Ett alternativ är att öka belastningen av befintliga kraftledningar på bekostnad av de säkerhetsmarginaler som finns. En av flera dimensionerande faktorer är risken för otillräckligt dämpade effektpendlingar mellan generatorer i kraftsystemet. Avhandlingen föreslår dämpning av effektpendlingar genom styrning av elpannor eller andra elektriska belastningar som huvudsakligen drar aktiv effekt. Detta demonstrerades vid ett fältförsök där pendlingar mellan ett mindre vattenkraftverk på 900 kW och övriga kraftsystemet dämpades genom att styra fyra värmefläktar på vardera 5 kW.



Avhandlingen inriktar sig på att relatera inverkan av styrbar aktiv effekt på effektpendlingar till kraftsystemets struktur. För detta ändamål används ett antal matematiska modeller, där den enklaste beskriver området där fältförsöket gjordes och den största är en modell av hela det svenska kraftsystemet. En modell av ett enkelt mekaniskt system med fjädrar och två massor används genomgående och avhandlingen visar att de fenomen som är relevanta i stor utsträckning kan beskrivas av denna modell. (Less)
Abstract
Environmental and economical aspects make it difficult to build new power lines and to reinforce existing ones. The continued growth in demand for electric power must therefore to a great extent be met by increased loading of available lines. A consequence is that power system damping is reduced, leading to a risk of poorly damped power oscillations between the generators. This thesis proposes the use of controlled active loads to increase damping of such electro-mechanical oscillations. The focus is on structural aspects of controller interaction and of sensor and actuator placement.



On-off control based on machine frequency in a single machine infinite bus system is analysed using energy function analysis and phase... (More)
Environmental and economical aspects make it difficult to build new power lines and to reinforce existing ones. The continued growth in demand for electric power must therefore to a great extent be met by increased loading of available lines. A consequence is that power system damping is reduced, leading to a risk of poorly damped power oscillations between the generators. This thesis proposes the use of controlled active loads to increase damping of such electro-mechanical oscillations. The focus is on structural aspects of controller interaction and of sensor and actuator placement.



On-off control based on machine frequency in a single machine infinite bus system is analysed using energy function analysis and phase plane plots. An on-off controller with estimated machine frequency as input has been implemented. At a field test it damped oscillations of a 0.9 MW hydro power generator by controlling a 20 kW load.



The linear analysis uses two power system models with three and twenty-three machines respectively. Each damper has active power as output and local bus frequency or machine frequency as input. The power system simulator EUROSTAG is used both for generation of the linearized models and for time simulations.



Measures of active power mode controllability and phase angle mode observability are obtained from the eigenvectors of the differential-algebraic models. The geographical variation in the network of these quantities is illustrated using the resemblance to bending modes of flexible mechanical structures. Eigenvalue sensitivities are used to determine suitable damper locations.



A spring-mass equivalent to an inter-area mode provides analytical expressions, that together with the concept of impedance matching explain the structural behaviour of the power systems. For large gains this is investigated using root locus plots. The effect of using two dampers is studied. For the three machine system this is done for all combinations of the two gains in a certain range. In the twenty-three machine case one gain takes only two values as the other is varied. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Professor Verghese, George, Department of Electrical Engineering and Computer Science, MIT, Cambridge, MA, USA
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Electronics and Electrical technology, controller interaction, mode controllability, mode observability, mechanical equivalent, linear differential-algebraic equations, modal analysis, active power, power system damping, electro-mechanical oscillations, Elektronik och elektroteknik, Automation, robotics, control engineering, Automatiska system, robotteknik, reglerteknik
pages
196 pages
publisher
IEA, LTH, Box 118, SE-221 00 Lund, Sweden,
defense location
Room M:B, M-building, LTH
defense date
1997-05-16 10:15
external identifiers
  • Other:ISRN: LUTEDX/(TEIE-1014)/1-196/(1997)
ISBN
91-88934-05-5
language
English
LU publication?
yes
id
4746cd9f-1711-4077-9bef-67dcd3703995 (old id 18213)
date added to LUP
2007-05-24 10:44:16
date last changed
2016-09-19 08:45:14
@misc{4746cd9f-1711-4077-9bef-67dcd3703995,
  abstract     = {Environmental and economical aspects make it difficult to build new power lines and to reinforce existing ones. The continued growth in demand for electric power must therefore to a great extent be met by increased loading of available lines. A consequence is that power system damping is reduced, leading to a risk of poorly damped power oscillations between the generators. This thesis proposes the use of controlled active loads to increase damping of such electro-mechanical oscillations. The focus is on structural aspects of controller interaction and of sensor and actuator placement.<br/><br>
<br/><br>
On-off control based on machine frequency in a single machine infinite bus system is analysed using energy function analysis and phase plane plots. An on-off controller with estimated machine frequency as input has been implemented. At a field test it damped oscillations of a 0.9 MW hydro power generator by controlling a 20 kW load.<br/><br>
<br/><br>
The linear analysis uses two power system models with three and twenty-three machines respectively. Each damper has active power as output and local bus frequency or machine frequency as input. The power system simulator EUROSTAG is used both for generation of the linearized models and for time simulations.<br/><br>
<br/><br>
Measures of active power mode controllability and phase angle mode observability are obtained from the eigenvectors of the differential-algebraic models. The geographical variation in the network of these quantities is illustrated using the resemblance to bending modes of flexible mechanical structures. Eigenvalue sensitivities are used to determine suitable damper locations.<br/><br>
<br/><br>
A spring-mass equivalent to an inter-area mode provides analytical expressions, that together with the concept of impedance matching explain the structural behaviour of the power systems. For large gains this is investigated using root locus plots. The effect of using two dampers is studied. For the three machine system this is done for all combinations of the two gains in a certain range. In the twenty-three machine case one gain takes only two values as the other is varied.},
  author       = {Samuelsson, Olof},
  isbn         = {91-88934-05-5},
  keyword      = {Electronics and Electrical technology,controller interaction,mode controllability,mode observability,mechanical equivalent,linear differential-algebraic equations,modal analysis,active power,power system damping,electro-mechanical oscillations,Elektronik och elektroteknik,Automation,robotics,control engineering,Automatiska system,robotteknik,reglerteknik},
  language     = {eng},
  pages        = {196},
  publisher    = {ARRAY(0x97cf6f0)},
  title        = {Power System Damping - Structural Aspects of Controlling Active Power},
  year         = {1997},
}