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© 2002 F. Alvarado
Slides to be available from http://www.pserc.wisc.edu
Challenges in Power System Control
Fernando Alvarado*
Electrical and Computer Engineering
University of Wisconsin-Madison
(*) Vice-chair, IEEE-USA Energy Policy Committee
Senior Consultant, Christensen Associates
NSF/EPRI Workshop: Economics
Electric Power and Adaptive Systems
Arlington, VA, March 28, 2002
28 March 2002
Challenges in Power System Control
PSERC
How 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
28 March 2002
Challenges in Power System Control
“Everything that can be invented
has been invented,” Charles H. Duell,
commissioner, U.S. Patent Office, 1899
“Gee, power systems is an old area
what are you going to do?”
anonymous sources paraphrased,
National Science Foundation, circa 2002
Themes of this talk
Desirable power system attributes
Interdependencies and complexity
Challenge: Eliminate perception of complexity
Market design challenges
Can the system control the market?
Can the market control the system?
Control challenges
Make the system fundamentally stable
Make the system infinitely responsive
Make the system heal itself
28 March 2002
Challenges in Power System Control
© 2001 F. Alvarado
Desirable system attributes
It depends on who you ask!
End users
Investors/marketers
Regulators/legislators
Engineers/operators
Economists
Control engineers/researchers
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Challenges in Power System Control
End user attributes
Attribute
Importance
Free
5
Always there
4
Pollution free, invisible
3
Glitchless, perfect waveform
1
Exact frequency
1
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Challenges in Power System Control
Investor/marketer attributes
Attribute
Importance
5
Profitable
Understandable rules
2
Contractually feasible
1
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Challenges in Power System Control
Regulator/legislator attributes
Attribute
Importance
Cheap
5
Environmentally sound
4
Reliable
3
Fair to all
2
Simple
1
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Challenges in Power System Control
Engineer/operator attributes
Attribute
Importance
Reliable
5
Secure, robust
4
Flexible
3
Economic
2
Clean
1
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Challenges in Power System Control
Economist attributes
Attribute
Importance
Efficient
5
Efficient
5
Efficient
5
Fair
1
Simple
1
28 March 2002
Challenges in Power System Control
Control viewpoint attributes
Attribute
Importance
Stable
5
Robust, fault tolerant
4
Dispatchable
3
Nimble, flexible
2
Observable
1
28 March 2002
Challenges in Power System Control
Complexity can make the
system 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
28 March 2002
Challenges in Power System Control
© 2001 F. Alvarado
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 untested
New problems may still arise
Challenge: create the illusion of simplicity
28 March 2002
Challenges in Power System Control
© 2001 F. Alvarado
Impact of less centralization
Less centralized planning can lead to
“harder to control” systems
No natural incentive to consider systemwide impact of individual actions
Less centralized operation has pitfalls
A complex system operating under stress
requires coordination of actions
Emergency actions may not be optimal
under time and complexity pressures
28 March 2002
Challenges in Power System Control
© 2001 F. Alvarado
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 effects
Action by one party to gain small additional
profits can greatly increase cost to others
“The gate of the transistor”, or
can one MVAR really be worth that many MW?
28 March 2002
Challenges in Power System Control
© 2001 F. Alvarado
Some 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 system behavior
Interactions among controls
Flow control devices can affect flows in remote
regions of a system
Further understanding of voltage collapse
Countermeasures to malicious actions
Including failure mitigation and restoration
28 March 2002
Challenges in Power System Control
© 2001 F. Alvarado
Complexity reduction
challenges
• 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
28 March 2002
Challenges in Power System Control
© 2001 F. Alvarado
Additional 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
28 March 2002
Challenges in Power System Control
© 2001 F. Alvarado
Research on structural and
policy 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 power
Power system market power has unique features
Beneficial actions to one party can affect
another party adversely
28 March 2002
Challenges in Power System Control
© 2001 F. Alvarado
Additional 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
28 March 2002
Challenges in Power System Control
© 2001 F. Alvarado
It is the nature of markets to result
in higher volatility.
Volatility is not, in and of itself, bad!
variability
volatility
Deregulated
Location or time period
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Challenges in Power System Control
cost
cost
Regulated
variability
volatility
System 2
seam
System 1
28 March 2002
Seams:
spatial
and
temporal
seam
cost
System 1
cost
Deregulated: watch
our for those seams
Challenges in Power System Control
cost
System 2
cost
Regulated: easier
to control seams
Concerns about
interdependencies
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 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
28 March 2002
Challenges in Power System Control
© 2001 F. Alvarado
Some 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
28 March 2002
Challenges in Power System Control
© 2001 F. Alvarado
Related challenge: funding
Attract smart people to power engineering
NSF funding crucial
Higher salaries in industry key
Intellectual and practical excitement important!
New sensors, computing and communication create
new control opportunities
Foster new practical ideas, reject unrealistic ones
Coordinate academic research with industrial experience
Support quality research on a time scale of 10 years
Many problems require years of study
If academic power systems research continues to wither,
the technological leadership will move further abroad
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Challenges in Power System Control
Seven interesting examples of
research in the control area
“Thinking”
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Challenges in Power System Control
Example #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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Challenges in Power System Control
Example #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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Challenges in Power System Control
Example #3: Inherently stable
controls
Adding a new component to the
system guarantees that the system if
more stable than before the
component is added
Yes, they do exist
One 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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Challenges in Power System Control
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?
28 March 2002
Challenges in Power System Control
Example #5: Congestion, properly
managed, stabilizes the system!
Idea has been shown by yours truly
Others have dismissed this as crazy!!!
Congestion is no good for economy
Congested system is less efficient
But congestion decouples and adds rigidity
Mathematics: eigenvalue inclusion theory
Is the converse also true?
Will a larger single grid be LESS STABLE?
YES. But we CAN make it work!
28 March 2002
Challenges in Power System Control
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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Challenges in Power System Control
Example #7: ________________
Fill in your pet idea not yet mentioned
Box
28 March 2002
Challenges in Power System Control
Grand Mini challenges
Develop self-healing stable market-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 electricity
Scratch 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