Sixth Northwest Conservation & Electric Power Plan
Adding Incremental Flexibility to the
Pacific Northwest Power System?
Maury Galbraith
Northwest Power and Conservation Council
Portland, OR
August 21, 2008
System Flexibility Defined in Terms of
Ancillary Services:
• Continuous Response:
– Regulation
– Load Following
• Contingency Response:
– Spinning Reserve
– Non-spinning Reserve
– Replacement (Supplemental) Reserve
• Other Services:
– Voltage Control
– Black Start
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Regulation Services:
• Regulation is the use of online generation that is
equipped with automatic generation control (AGC) to
track the moment-to-moment fluctuations in customer
loads and generation
– Compensates for short-term largely random fluctuations in load
and generation
– Automatic: Requires AGC
– Response Speed: ~ 1 minute
– Duration: minutes
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Load Following Services:
• Load Following is the use of online generation to track
the intra- and inter-hour changes in customer loads and
generation
– Compensates for larger, slower and generally predictable swings
associated with the daily load cycle or wind generation ramping
events
– Can be manual
– Response Speed: ~ 10 minutes
– Duration: 10 minutes to hours
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Scheduling and Load Balancing in the Pacific
Northwest:
90
80
Regulation Up
70
Intra-hour Load Following
MW
60
50
Inter-hour Load Following
Regulation Down
40
30
20
10
0
-20 -15 -10 -5
0
5
10 15 20 25 30 35 40 45 50 55
Previous Schedule
Final Schedule
0
5
10
Actual Generation
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Control Area Operation:
• Operators focus on maintaining the net interchange with
neighboring Control Areas at the final scheduled amount
– Accurately measuring net load is difficult because of large
number of loads and system losses
– Easier to accurately measure flows on tie lines to neighboring
Control Areas because of small number of lines
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NERC Control Performance Standards:
• Impossible to perfectly match generation and load
• NERC has established Control Performance Standards
(CPS) to determine the amount of imbalance the is
permissible for reliability purposes
• System frequency is the fundamental indicator of
Interconnection health
– Frequency drops when load > generation
– Frequency rises when load < generation
– Target = 60 Hz
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NERC Control Performance Standards:
• Area Control Error (ACE) is a measure of a Control
Area’s contribution to Interconnection health
– ACE is negative when load > generation (under-generation)
– ACE is positive when load < generation (over-generation)
– ACE is zero when load = generation
• CPS1 is an annual standard that measures the relationship
between the Control Area’s ACE and the Interconnection
frequency.
• CPS2 is a monthly standard that limits the Control Area’s
maximum ACE.
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Implications of NERC CPS for the Provision
of Incremental System Flexibility:
• Load and generation volatility is important to a Control
Area if it affects CPS performance and the costs of
staying within NERC CPS bounds
• CPS compliance is Pass/Fail
– Must simultaneously satisfy both CPS1 and CPS2
– Reducing ACE is of little benefit unless the reduction moves the
Control Area from non-compliance to compliance
• CPS compliance is measured over long time frames
– Good performance can offset poor performance
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Does the Region Need to Augment Power
System Flexibility?
• Continued growth of wind generation is likely to increase
the need for incremental system flexibility
Appears to be
the most
significant
factor
– Typically adds generation volatility at the seconds to minutes time
scale increasing the demand for regulation
– Increases the frequency and sometimes the magnitude of subhourly and hourly ramping events increasing the demand for load
following
– The need to shape wind output to load over longer time scales may
increase the value of some energy storage alternatives
• Environmental constraints are likely to continue to
constrain existing hydro system flexibility
– The tradeoff between system flexibility and environmental
protection is not well-understood
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Sources of Incremental System Flexibility
See: Wind Integration Action Plan – Appendix D
• Generation Technologies
• Storage Technologies
• Demand-side Options
• System Operation Options
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Generation Technologies
Status
Flexibility
Application
SCCT (e.g. LM6000, LMS100)
Mature
Reg/ LF
Reciprocating Engines
Mature
Reg/ LF
Duct Firing Added to CCCT
Mature
Reg
Capacity Added to Existing Hydro Projects
Mature
Reg/ LF
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Storage Technologies
Status
Flexibility
Application
Pumped Storage Hydro
Mature
Reg/ LF
Batteries - Conventional
Mature
Reg/ LF
Batteries – Flow/Redox
Beta
Reg/ LF
Early Commercial
Reg/ LF
In Development
Reg/ LF
Mature for Cavern
Reg/ LF
Batteries - NAS
Capacitors/ Ultracapacitors
Compressed Air
Plug-in Hybrid Electric Vehicles
Conceptual
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Demand-side Options
Status
Flexibility
Application
Load Interruption Rights
Mature
LF
Dispatchable Distributed Generation
Mature
LF
Dispatchable Load Cycling
Mature
Reg/ LF
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System Operation Options
AGC Added to Existing Resources
ACE Diversity Exchange
Standardized Ancillary Services Contracts
Status
Flexibility
Application
Mature
Reg
In Development
Reg/LF
Reg/LF
Improved Wind Prediction
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Discussion Points:
• Have we accurately characterized the system flexibility
issues?
• Have we listed all of the major options available to
increase system flexibility?
• How should we prioritize our investigation of the issues
and options?
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