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

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

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.

Power System Decision Timescales

Electric Grid Overview www.eia.doe.gov

NERC www.nerc.com “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

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

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.

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.

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

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

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

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

Wind Fluctuations in Texas

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

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

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.

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.

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

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