28 march 2002challenges in power system control fernando alvarado* electrical and computer...
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28 March 2002 Challenges in Power System Control
Challenges in Power System ControlChallenges in Power System Control
Fernando Alvarado*Electrical and Computer Engineering
University of Wisconsin-Madison
PSERC
NSF/EPRI Workshop: EconomicsElectric Power and Adaptive SystemsArlington, VA, March 28, 2002
(*) Vice-chair, IEEE-USA Energy Policy CommitteeSenior Consultant, Christensen Associates
Slides to be available from http://www.pserc.wisc.edu© 2002 F. Alvarado
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28 March 2002 Challenges in Power System Control
How I got hereHow I got here
Bruce:I want you to give a 30/45 minute talk on
challenges in control of power systems
Fernando:It is going to be difficult to prepare it
Bruce:I want the big picture
Fernando:Oh, the big picture is easy. I thought you
wanted details
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“Gee, power systems is an old areawhat are you going to do?”
anonymous sources paraphrased, National Science Foundation, circa 2002
“Everything that can be inventedhas been invented,” Charles H. Duell, commissioner, U.S. Patent Office, 1899
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28 March 2002 Challenges in Power System Control
Themes of this talkThemes of this talk
Desirable power system attributes
Interdependencies and complexityChallenge: Eliminate perception of complexity
Market design challengesCan the system control the market?
Can the market control the system?
Control challengesMake the system fundamentally stable
Make the system infinitely responsive
Make the system heal itself
© 2001 F. Alvarado
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28 March 2002 Challenges in Power System Control
Desirable system attributesDesirable system attributes
It depends on who you ask!End users
Investors/marketers
Regulators/legislators
Engineers/operators
Economists
Control engineers/researchers
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28 March 2002 Challenges in Power System Control
End user attributesEnd user attributes
Attribute Importance
5
Always there 4
Pollution free, invisible 3
Glitchless, perfect waveform 1
Exact frequency 1
Free
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28 March 2002 Challenges in Power System Control
Investor/marketer attributesInvestor/marketer attributes
Attribute Importance
5
Understandable rules 2
Contractually feasible 1
Profitable
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28 March 2002 Challenges in Power System Control
Regulator/legislator attributesRegulator/legislator attributes
Attribute Importance
5
4
3
2
1
Cheap
Environmentally sound
Reliable
Fair to all
Simple
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28 March 2002 Challenges in Power System Control
Engineer/operator attributesEngineer/operator attributes
Attribute Importance
5
4
Flexible 3
Economic 2
Clean 1
Reliable
Secure, robust
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28 March 2002 Challenges in Power System Control
Economist attributesEconomist attributes
Attribute Importance
5
5
5
Fair 1
Simple 1
Efficient
Efficient
Efficient
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28 March 2002 Challenges in Power System Control
Control viewpoint attributesControl viewpoint attributes
Attribute Importance
5
Robust, fault tolerant 4
Dispatchable 3
Nimble, flexible 2
Observable 1
Stable
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28 March 2002 Challenges in Power System Control
Complexity can make the Complexity can make the system vulnerablesystem vulnerable
The transmission system was designed area by area. Inter-area interconnections evolved in order to
Perform economy exchanges
Enable assistance during emergencies
Design and operation presumes cooperation among grid participants
Deregulation of the electric market leads to greater utilization of the grid
© 2001 F. Alvarado
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28 March 2002 Challenges in Power System Control
Is complexity increasing?Is complexity increasing?
New patterns of grid utilization result in new flow and congestion patterns
Less ability to control all aspects of the system introduces vulnerabilities
“Humans in the loop” requires the development of intuition
A larger interconnection is untestedNew problems may still arise
© 2001 F. Alvarado
Challenge: create the illusion of simplicity
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28 March 2002 Challenges in Power System Control
Impact of less centralizationImpact of less centralization
Less centralized planningplanning can lead to “harder to control” systems
No naturalnatural incentive to consider system-wide impact of individual actions
Less centralized operationoperation has pitfallsA complex system operating under stress
requires coordination of actions
Emergency actions may not be optimal under time and complexity pressures
© 2001 F. Alvarado
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28 March 2002 Challenges in Power System Control
What do markets do?What do markets do?
Markets often align self-serving interests with society's interests
Self-serving behavior can affect others adversely (even without market power)
The grid magnifies adverse effectsAction by one party to gain small
additional profits can greatly increase cost to others
© 2001 F. Alvarado
“The gate of the transistor”, orcan one MVAR really be worth that many MW?
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28 March 2002 Challenges in Power System Control
Some challengesSome challenges
Understanding stability when markets control significant aspects of the system
The combination of economies of scale in supply and changing congestion patterns can lead to erratic and unstable systemsystem behavior
Interactions among controlsFlow control devices can affect flows in remote
regions of a system
Further understanding of voltage collapse
Countermeasures to malicious actionsIncluding failure mitigation and restoration
© 2001 F. Alvarado
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28 March 2002 Challenges in Power System Control
Complexity reduction Complexity reduction challengeschallenges
• Study complexity-reduction technologies– Breakup the power grid by use of DC and/or FACTS
technologies– Use dispersed technologies to mitigate the effect of
failures– Build a grid that Wall Street can understand?
• Methodologies for rapid understanding of a system under crisis conditions– The extremely large size of the grid has led to large
computational challenges
• Uncertainty and risk management tools for security management in the presence of large-scale system threats
© 2001 F. Alvarado
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28 March 2002 Challenges in Power System Control
Additional control challengesAdditional control challenges
Understand threats and failure modes that occur as a result of complexity
Develop tools to mitigate the effects of complexity
Mitigate the impact of complexity by ab-initio design
Understand cascading failures
© 2001 F. Alvarado
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28 March 2002 Challenges in Power System Control
Research on structural and Research on structural and policy implications on securitypolicy implications on security
Self interests can differ greatly from the common good
Aligning the two by appropriate means can be difficult as a result of interdependencies complexities and vested interests
A particular concern is market powerPower system market power has unique
features
Beneficial actions to one party can affect another party adversely
© 2001 F. Alvarado
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28 March 2002 Challenges in Power System Control
Additional questionsAdditional questions
Understanding impact of rules for markets, for ISOs and for end users
Measure security taking into account uncertainties introduced by separate ownership of system assets
Better understanding of conditions that hamper competition
© 2001 F. Alvarado
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28 March 2002 Challenges in Power System Control
Regulated cost
variabilityvolatility
Deregulated cost
variabilityvolatility
It is the nature of markets to resultin higher volatility.
Volatility is not, in and of itself, bad!
Location or time period
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28 March 2002 Challenges in Power System Control
System 1 cost
System 2
cost
seam
System 1
cost
System 2
cost
seam
Regulated: easier to control seams Deregulated: watch
our for those seams
Seams:spatial
andtemporal
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28 March 2002 Challenges in Power System Control
Concerns about Concerns about interdependenciesinterdependencies
Dependency of the telecommunication and Web infrastructure on electric power
Consider impact that energy conservation efforts can have on vulnerability
Increased penetration of power electronic devices can have an undesirable effectundesirable effect on network security as a result of the removal of the "natural" voltage and frequency dependencies of loads
Distributed generation can make systems less vulnerable
© 2001 F. Alvarado
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28 March 2002 Challenges in Power System Control
Some specific activitiesSome specific activities
Dynamic interaction between market and power system can induce instabilities
Extended eigenanalysis including discrete effects We may have the first evidence of this in
practice
Interdependency of markets, policymaking and reliability can lead to system failure
Unreliability: any involuntary curtailment of load
Load as a resource
© 2001 F. Alvarado
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28 March 2002 Challenges in Power System Control
Related challenge: fundingRelated challenge: funding
Attract smart people to power engineeringNSF funding crucialHigher salaries in industry keyIntellectual and practical excitement important!
New sensors, computing and communication create new control opportunities
Foster new practical ideas, reject unrealistic onesCoordinate academic research with industrial experience
Support quality research on a time scale of 10 yearsMany problems require years of studyIf academic power systems research continues to wither,
the technological leadership will move further abroad
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28 March 2002 Challenges in Power System Control
Seven interesting examples of Seven interesting examples of research in the control arearesearch in the control area
“Thinking”
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28 March 2002 Challenges in Power System Control
Example #1: WAMSExample #1: WAMS
A global view of the status of the grid is essential
Controls based in insufficient information are incapable of dealing with today’s complexities
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28 March 2002 Challenges in Power System Control
Example #2: Cascading outagesExample #2: Cascading outages
Should we try to prevent them?Maybe they are inevitable!
Work on self-organized criticality suggests this
If so, would we not be better off by learning to cope with them?
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28 March 2002 Challenges in Power System Control
Example #3: Inherently stable Example #3: Inherently stable controlscontrols
Adding a new component to the system guarantees that the system if more stable than before the component is added
Yes, they do existOne such control strategy was
developed for FACTS devices by J. Gronquist
Can we generalize this type of control?
What do we give up?
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28 March 2002 Challenges in Power System Control
Example #4: Break up the grid?Example #4: Break up the grid?
Would we be better off by splitting the grid into many Texas-sized grids connected solely by DC?
Casazza, others have suggested it
A phase shifter on every line???Do phase shifters break up the grid?
Really?
How about even smaller grids?Micro-grids?
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28 March 2002 Challenges in Power System Control
Example #5: Congestion, properly Example #5: Congestion, properly managed, stabilizes the system!managed, stabilizes the system!
Idea has been shown by yours trulyOthers have dismissed this as crazy!!!
Congestion is no good for economyCongested system is less efficient
But congestion decouples and adds rigidityMathematics: eigenvalue inclusion
theoryIs the converse also true?Will a larger single grid be LESS STABLE?
YES. But we CAN make it work!
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28 March 2002 Challenges in Power System Control
Example #6: Control by price?Example #6: Control by price?
And by price alone!Yes or no?
YES!Shown by Glavitsch and yours truly
But…Difficult to attain
Linearity makes it difficult! (surprise here)
Economies of scale make it hard
Not everyone is “on their toes”
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28 March 2002 Challenges in Power System Control
Example #7: ________________Example #7: ________________
Fill in your pet idea not yet mentioned
Box
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Grand Mini challengesGrand Mini challenges
Develop self-healing stable market-drivenmarket-driven controls that adapt to changing conditions
Provide effective control by market means alone to the extent possible
Monitor and manage environmental externalities
Develop new ways of delivering electricityScratch that: develop new ways of meeting the user’s
desire for electric energy in general
Design controls with “humans in the loop”Make a single continental-sized grid work!Design for apparent simplicity!
The bottom line: the needed work is multidisciplinary