Wyoming Infrastructure Authority

(October, 2010)

1) Market Characteristics for Efficient Integration of Variable Generation in the Western Interconnection
http://www.nrel.gov/docs/fy10osti/48192.pdf (PDF 1.2 MB)

Authors: Michael Milligan and Brendan Kirby

The Western Electricity Coordinating Council (WECC) convened the Variable Generation Subcommittee (VGS) in 2009. The VGS was commissioned to address all issues related to the predicted increasing penetration of variable generation on reliability, both in the operating and planning time frames. The VGS was split into four Work Groups: Operations, Planning, Markets, and Technology. The Markets Workgroup was tasked with developing a white paper to address the role of electricity markets to help manage variable generation (VG). As part of the white paper effort, prior work from the National Renewable Energy Laboratory (NREL) was used to provide evidence of how markets help with reliable power system operation, both with and without VG. This report, adapted from prior reports and research by the authors and others, was used in the development VGS Market White Paper, still in draft form at the time of this writing.

2) Combining Balancing Areas’ Variability: Impacts on Wind Integration in the Western Interconnection
http://www.nrel.gov/docs/fy10osti/48249.pdf (PDF 881 KB)

Authors: Michael Milligan, Brendan Kirby, and Stephen Beuning

In this paper, we illustrate several ways in which balancing area cooperation can improve the system’s ability to integrate wind energy. We focus on a description of an Energy Imbalance Service (EIS) that has been proposed by WECC’s Seams Issues Subcommittee, and illustrate the potential benefits of the EIS or other form of BA cooperation in the Pacific Northwest. We show that the two primary power system characteristics that help with wind integration are balancing area size and fast (5 minutes) economic dispatch and scheduling. Several approaches can be utilized to acquire these characteristics, including large, fast energy markets (with or without coordinated unit commitment), physical or virtual consolidation, or innovative dynamic scheduling or related measures. Our analysis shows that coordination reduces ramping requirements both operationally and in the planning domain; coordination will result in the need for less flexible generation and lower cost. Further, we find that the approaches discussed in this paper would be efficient even without significant development of wind or other variable generation resources.

3) Utilizing Load Response for Wind and Solar Integration and Power System Reliability
http://www.nrel.gov/docs/fy10osti/48247.pdf (PDF 749 KB)

Authors: Michael Milligan and Brendan Kirby

Demand response is a proven set of technologies that have been used by utilities to improve reliability for decades. Improvements in communications and controls now make it practical to obtain regulation and contingency reserves as well as peak reduction from responsive loads. Real-time price response is also technically feasible though regulatory barriers exist. FERC has assessed the current state of demand response in the United States and concluded that significantly greater capability exists. Increasing the pool of responsive resources is beneficial for wind and solar since they add variability and uncertainty to the power system at the same time that they displace generation that itself can provide response. Both voluntary price response and command and control are useful. Variable generation up-ramps are typically not a reliability concern since wind or solar can be spilled. Up-ramps are an economic concern that load response can help with. Down-ramps can be a reliability concern and are certainly an economic concern. Here too load response can help. Wind and solar ramps are slower than conventional contingencies. Responding to large ramps will require price responsive load and may require a new reserve that is similar to supplemental operating reserve. Renewable generation advocates should work to remove barriers to demand response.

4)Advancing Wind Integration Study Methodologies: Implications of Higher Levels of Wind
http://www.nrel.gov/docs/fy10osti/48944.pdf (PDF 2.0 MB)

Authors: Michael Milligan, Erik Ela, Debra Lew, Dave Corbus, and Yih-huei Wan

Wind integration studies are now routinely undertaken by utilities and system operators to investigate the operational impacts of the variability and uncertainty of wind power on the grid. There are widely adopted techniques and assumptions that are used to model system operation, examine impacts on the regulation, load following, and unit commitment timeframes, and quantify costs. As wind penetration levels increase, some of the assumptions and methodologies are no longer valid and new methodologies have been devised. Based on involvement in conducting studies, reviewing studies, and/or developing datasets for studies in WECC, the Eastern Interconnect, Hawaii, and other regions, the authors report on the evolution of techniques to better model high penetrations (generally, 20% or more energy penetration) of wind energy.

Best regards,

Kelly Wang
NREL – Transmission and Grid Integration
1617 Cole Blvd., MS 3811
Golden, CO 80401
303-384-6930