Integrating Wind Energy into Large Power Systems

wind tubrines and full moon
(cc) TPMartins

Judy Chang and Kamen Madjarov, consultants from The Brattle Group, estimate that approximately 1,000 megawatts of additional generator regulation service will be needed to balance an extra 50,000 megawatts of wind energy resources in a large regional transmission organization (RTO) power system. They presented these estimates at the Infocast Wind & Solar Integration Summit in Phoenix, Arizona yesterday.

Chang and Madjarov used the Renewable Integration Model (RIM), which was jointly developed by The Brattle Group and Pacific Gas & Electric, to quantify the potential effects of integrating variable generation on power systems. They created a case study that utilized empirical wind and load data from their California experience and applied them to a stylized 100,000 MW system to estimate the effects of a high wind penetration scenario that satisfied a 25 percent renewable portfolio standard. By characterizing the statistical relationships between the forecasting errors and variability of generation and load over a range of time frames, the model estimates the regulation, load following, and day-ahead generation commitment requirements and costs of balancing variable energy resources on systems of various sizes and levels of intermittent generation and load.

In their case study, the additional regulation requirements to integrate an extra 50,000 MW of wind generation ranged from 500 MW during the fall to 1,300 MW during the spring, due to the different seasonal patterns of generation. “Our estimates demonstrate that the additional generator regulation service needed to integrate significant amounts of wind generation is fairly modest on a large system, particularly when generation patterns are diverse,” said Chang. “Smaller systems with more concentrated wind resources will tend to experience much larger effects,” she added. There will also be additional demands for load following and day-ahead unit commitment.

The simulations accommodate sub-hourly scheduling, various definitions of the required balancing services, and both RTO and non-RTO industry structures. The modeling tool also allows for simple updates of balancing needs as new operational and forecasting experience becomes available. As Chang and Madjarov explained during the conference, this approach is uniquely well suited to estimate the likely need for additional regulation service under the proposed Schedule 10 of the pro forma transmission tariff, as well as the potential effects on the load following needs associated with intra-hour scheduling using best available forecast information as proposed in the Federal Energy Regulation Commission’s November 2010 Notice of Proposed Rulemaking on the Integration of Variable Energy Resources.

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