Download Transmission Topology Control for System Efficiency

Transmission Topology Control for System Efficiency
Simulations on PJM Real Time Markets
Pablo A. Ruiz
M. C. Caramanis, E. Goldis, B. Keshavamurthy, X. Li, M. Patel,
C. R. Philbrick, A. M. Rudkevich, R. D. Tabors, T. B. Tsuchida.
Super Session on Transmission System Efficiency and Reliability Improvements
IEEE PES General Meeting
Vancouver, BC, July 25, 2013
Copyright © 2013 The Brattle Group, Inc.
www.brattle.com
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Agenda
♦ Topology Control Algorithms (TCA): Objectives and Motivation
♦ Illustration of Topology Control
♦ ARPA-E TCA Project
♦ Summary of Simulation Results on PJM RT Markets
♦ Concluding Remarks
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TCA Objectives
The goal of tractable control of the transmission network topology
is to extract more value out of transmission facilities:
1. Significantly lower generation costs
2. Provide additional operational controls
♦ manage congestion
♦ respond during contingency situations
3. Enable higher levels of variable renewable penetration
4. Increase system reliability
TCA Timeframe: between a few days ahead up to real-time
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Congestion in RT Markets: PJM
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18-Jul-2013 15:30
18-Jul-2013 12:20
In the course of a day, congestion patterns and
prices can change significantly:
 Fuel diversity
 Lack of flexibility in the resource mix
Having the ability to dynamically increase transfer
capability from low price areas to high price areas
will help to relieve congestion, improve dispatch of
renewable resources, reduce dispatch costs and
increase system flexibility.
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7-bus Example: All Lines Closed
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7-bus Example: All Lines Closed
$40/MWh
$15/MWh
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7-bus Example:
Open Branch Fed by Congested Facility (Line 3 – 4)
Savings!
$40/MWh
$15/MWh
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Transmission Switching in PJM (Currently)
PJM has switching solutions that operators apply to alleviate congestion:
http://www.pjm.com/markets-and-operations/etools/oasis/system-information/switching-solutions.aspx
“The following is a list of potential transmission switching procedures identified by
PJM that may assist to reduce or eliminate transmission system congestion.
These identified potential transmission switching procedures may or may not be
implemented by PJM based upon system conditions, either projected or actual,
and ultimately are implemented solely at the discretion of PJM and its
Transmission Owners. This posting is for informational purposes only.
Consequently, PJM does not guarantee that any of these identified switching
procedures will be included in any market-based auctions or in the real time
analysis. Accordingly, PJM expressly disclaims any liability for financial
consequences that a Member may incur in taking action in reliance on these
informational postings.”
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ARPA-E TCA Project: Objectives and Focus
To develop a full-scale algorithm and software implementation
for transmission network topology control
♦ operating in conjunction with market engines for security-constrained
unit commitment (UC) and economic dispatch (ED);
♦ meeting tight computational effort requirements
The developed algorithms will be tested in a simulated
environment replicating PJM market operations.
Focus:
♦ Tractability: TCA must work on 13,000+ bus systems
♦ Dynamics: look-ahead TC decisions in ED and UC contexts
♦ Reliability: security constraints, transient stability and voltage criteria
met
♦ Impacts: economic and renewable integration benefit evaluation, with
expected production cost savings in PJM of over $100 million/year
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Basic TC Software Architecture
Topology,
Dispatch,
Commitment,
Marginal Costs
Contingency +
Voltage + Stability
Evaluation *
Topology Control
Voltage, MVA and Stability
Assessment: Feasible/Infeasible,
Constraints to Return to
Feasibility
The simulations in this presentation include contingency evaluation and
enforcement, but do not include voltage or transient stability evaluation
*
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PJM RT Market Test Systems
♦ Based on one operational power flow snapshot per hour (interval 30-35 minutes)
for three selected, representative historical weeks in 2010 (summer, shoulder and
winter weeks). Data taken from the power flows:
•
•
•
•
•
Transmission topology
Branch limits
Fixed interface constraint limits at historical value used by PJM for the same interval
Unit commitment
Fixed dispatch of hydro, wind, landfill, nuclear and reliability must-run thermal units for
the interval
• Loads, losses, interchange
♦ Approximately 13,400 nodes, and 400-500 dispatchable thermal PJM units
♦ About 3500 monitored facilities and 6000 single and multi-element contingencies
♦ Generation economic and constraint data from real-time market
♦ Network service requirements for all loads and generators
♦ No reserve requirements implemented in these models
♦ Model setup and results reviewed by PJM
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TC Economic Performance –
Metrics and Preliminary Results
Production Cost Savings = production cost without TCA (full topology)
– production costs with TCA
Cost of Congestion = production cost with transmission constraints
– production costs without transmission constraints
♦ The production or market Cost of Congestion defined above (different from congestion
rent, which can be many times larger) provides an upper bound on the maximum systemwide Production Cost Savings attainable with any transmission efficiency approach or
technology
The estimated annual savings in PJM RT markets under 2010
conditions are over $100 million
♦ Based on the production cost savings resulting from the weekly simulations*
*
Representative weeks of summer, winter and shoulder seasons were simulated.
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Notes on the TC Economic Performance
Realistic criteria:
♦ Solution time: 5 minutes (computation limit) for each interval solution
♦ Cost of switching: minimum savings of $100 per open or close breaker
operation required to switch
♦ Reliability
• Full security evaluation (6000 contingencies) and enforcement (included in the 5
minute time limit)
♦ Starting conditions: same historical conditions as the RT markets
Conservative estimate:
♦ Savings are in addition to any topology control action PJM implemented in that
week
♦ Standard, commercially available server (two 4-core 2.66-GHz Intel Xeon
processors, 24 GB of RAM)
♦ Many potential topology change options are not visible in the “reduced” busbranch power flow models (e.g., opening bus ties)
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Number of Topology Changes per Hour
(Preliminary)
Week
Metric
Branches
Open
Switched
Opened
Switched
Closed
Summer
Maximum
85
15
18
Median
56
5
5
Maximum
89
18
19
Median
57
5
4
Winter
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Different due to
weekly start with
full topology which
requires additional
openings and fewer
closings
Number of Topology Changes per Hour
(Preliminary)
A daily cycle of number of breakers open is
very evident in the summer week, with the
largest number of breakers opened
corresponding to hours with lower load
(early morning), and with more re-closings
as load increases to meet security
constraints.
Number of breakers open per hour seems
to increase during Winter week, indicating
that the average number of branches
opened has not reached a steady state
during the week (this is under
investigation, including looking at the
impacts of different starting topologies for
the weekly simulations). Initially, (Sunday),
topology did not change significantly since
congestion was limited.
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Summary of Breakers Operated (Preliminary)
Nominal kV
Summer
Week
Winter
Week
<200 kV
46%
51%
230 kV
26%
22%
345 kV
11%
14%
500 kV
11%
9%
765 kV
6%
4%
765 kV breakers are mostly opened
during low load periods, such as
during the weekend or very early
mornings, when they are not needed
for reliability, are lightly loaded, and
may cause overvoltages.
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Summary of Flow on Breakers Operated
(Preliminary)
Summer Week
Breakers Switched Open
Breakers Switched Close
nominal kV
median
flow MW
median
flow %
nominal kV
median
flow MW
median
flow %
115kV
47
24%
115kV
58
31%
138 kV
51
20%
138 kV
89
31%
230 kV
168
22%
230 kV
230
30%
345 kV
182
20%
345 kV
240
23%
500 kV
442
17%
500 kV
546
20%
765 kV
474
16%
765 kV
492
15%
Flows opened or closed are well below normal facility
ratings, and orders of magnitude below short circuit
ratings, reducing the expected maintenance required to
sustain the increased breaker duty
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Concluding Remarks and Work in Progress
♦ Most system operators employ TC today, mainly on an ad-hoc basis
using operators’ previous experience
♦ The TCA project will provide practical technology to enable transparent,
consistent and routine implementation of topology control with
significant efficiency gains
♦ The technology is being assessed on detailed models of PJM markets,
with review from PJM staff
• Hourly security-constrained TCA solutions are obtained in few minutes
• Simulations on detailed PJM RT market models indicate that annual PJM
savings are over $100 million (under 2010 conditions)
• Impacts on DA markets are expected to be significantly larger, since TC
could enable more efficient unit commitment, and will be analyzed next
♦ Off-line advisory tool planned to be ready for deployment by mid 2014
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Contact Info
Pablo A. Ruiz
The Brattle Group and Boston University,
[email protected]
(617) 234-5748
Please sign up for the TCA periodic updates!
References
[1]
[2]
[3]
[4]
P. A. Ruiz, J. M. Foster, A. Rudkevich and M. C. Caramanis, “Tractable transmission topology control using
sensitivity analysis,” IEEE Transactions on Power Systems, vol. 27, no. 3, Aug 2012, pp. 1550 – 1559.
P. A. Ruiz, A. Rudkevich, M. C. Caramanis, E. Goldis, E. Ntakou and C. R. Philbrick, “Reduced MIP formulation
for transmission topology control,” in Proc. 50th Allerton Conference on Communications, Control and Computing,
Monticello, IL, October 2012.
J. M. Foster, P. A. Ruiz, A. Rudkevich and M. C. Caramanis, “Economic and corrective applications of tractable
transmission topology control,” in Proc. 49th Allerton Conference on Communications, Control and Computing,
Monticello, IL, September 2011.
P. A. Ruiz, J. M. Foster, A. Rudkevich and M. C. Caramanis, “On fast transmission topology control heuristics,” in
Proc. 2011 IEEE Power and Energy Society General Meeting, Detroit, MI, July 2011.
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