1. Grid Integration of Intermittent Resources
Bernie Lesieutre
Engineering Physics 602, November 1, 2013

2. The Future?
Distributed Resources
256.com/solar
Concentrated Resources

3. Power System Operation
Power Flow and Optimal Power Flow solvers are tools to help analyze the grid and to help make decisions concerning the grid. Grid Operation must account for the availability of resources, dynamic and voltage stability, unanticipated events, uncertainty, etc. Decisions are made over different timescales.

4. Power System Decision Timescales

5. Electric Grid Overview

6. NERC
“The Interconnected power system shall be operated at all times so that the general system instability, uncontrolled separation, cascading outages, or voltage collapse will not occur as a result of any single contingency or multiple contingencies of sufficiently high likelihood” WECC Operating Handbook, 2005

7. Operation
The power grid is operated reliably. It is carefully monitored, and resources are kept available to respond to changing conditions.

8. Balancing Power
Without significant energy storage available, generation power and load power must balance.
If load exceeds generation, frequency drops.
If generation exceeds load, frequency rises.
Intermittent resources challenge this power balance.

9. Balancing Generation and Load
Measure: “ACE” – Area Control Error
Monitored in Balancing Authorities
Automatic Generation Control (AGC) adjusts generation every 4 seconds.
Penalties for non-compliance.
Generation Reserves: for tracking load, for responding to disturbances.

10. ACE X Area Interchange (Power) ACE Interchange Error Frequency Error
local
system

11. Challenge Intermittent Resources
Replace existing resources for energy, displacing traditional controls
Increase the need for controls

12. Challenge X Area Interchange (Power)
ACE
X Area Interchange (Power)
Need more dispatchable resources to track load and intermittent resource variability.

13. Challenge X Area Interchange (Power)
ACE
X Area Interchange (Power)
Need reserves to guard against (wind) power fluctuations and failure.

14. Wind Fluctuations in Texas

15. Wind Failure in Texas, Feb 2008
Loss of 1400 MW
Dropped 1100 MW
Of “Interruptible” load.
Load can be a resource. Are there limits?

16. Electricity Markets
Allow competition of generating resources, and demand.
Markets operate over different timescales
5 minutes (“real time”).
Hourly/Day-ahead: supports resource commitment.
Long term: capacity and transmission rights.
Details differ by market

17. Market Challenges
Intermittent resources are challenged by and challenge market operations:
What is the value of their “capacity”?
How well can production be anticipated one day in advance? Under-committing wind, over-commits other resources. Over-committing wind may cause reliability concerns.
How might uncertainty affect day-ahead and real-time markets? This could potentially skew market prices.

18. MISO: Load schedule
2012 Appendix, State of the Market Report for the Midwest ISO, p. A-43
97-98% of load is scheduled in the day-ahead market.

19. MISO: Wind Schedule
2012 State of the Market Report for the Midwest ISO, p. 43

20. Challenges
Intermittent resources challenge the traditional operation of the electric grid.
They challenge and are challenged by market dispatch.
New approaches and technologies can help:
Energy storage: Central vs. Distributed
Load as a resource for energy reserves and market participation