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Embracing Wind

Integrating renewables in New York.

Fortnightly Magazine - May 2011

the potential to over- or under-commit other generation resources to meet forecast load when wind generation—which isn’t required to offer into the day-ahead market—injects megawatts in the real-time market. After the day-ahead commitment, updated wind forecasts, which are provided in 15-minute intervals, are evaluated in the NYISO real-time commitment and dispatch processes. The wind forecast allows the NYISO to produce more efficient commitment decisions in real-time and allows more efficient transaction scheduling with neighboring control areas.

To enhance the NYISO’s operational control of New York wind resources in order to increase the ability to reliably and efficiently operate the New York transmission system—and to accommodate increased levels of wind powered resources—the NYISO in 2009 implemented the capability to direct wind resources to reduce their output when necessary and economically appropriate. The integration of increased levels of wind will be facilitated by using the NYISO’s market software to evaluate the economic offers submitted by all generation resources, including wind plants, to determine the most cost-effective way to address reliability issues (see Figure 3) . Integration of wind plants into NYISO’s real-time dispatch tools serves several objectives, including:

• Minimizing less-efficient manual out-of-market intervention by system operators or wind plant operators to address system reliability issues;

• Allowing wind resources to indicate their economic willingness to generate, identifying the most efficient resources to address constraints and incorporate energy reduction instructions into the market-clearing price;

• Evaluating the operation of wind plants on a five-minute basis to minimize the period and amount of generation curtailments; and

• Enhancing the reliability of the transmission grid and increasing the utilization of the transmission system.

Before the implementation of this feature, wind plants were subject to more negative pricing intervals. Negative prices mean generation has to pay the grid operator for every megawatt it generates. Such pricing patterns occur when wind generation is bottled due to transmission limitations. The negative prices drive wind plants off line, which can also cause reliability problems. Allowing wind plants to be dispatched downwards allows them to ride through congested intervals without pushing the entire plant off-line.

Broader Regional Markets

The intermittency of wind generation can be accommodated more effectively when the balancing area is large. This means that regional coordination is essential as we increase the proportion of wind and other intermittent sources of renewable power. The NYISO is working with its neighbors to implement an initiative called “Broader Regional Markets” that allows this to happen.

The broader regional initiative involves more frequent interchanges with neighboring control areas (currently interchanges are done hourly), coordinated congestion management (where transmission limitations are alleviated by re-dispatching generation on a regional basis), consistent pricing at power interchange points, and charging congestion costs to transactions that cause congestion.

NYISO will be implementing its first Broader Regional Market rule this summer. In this implementation, NYISO will increase the frequency of interchanges with Hydro Quebec from one every hour to once every 15 minutes. This will be increased to once every five minutes by 2012. This increased frequency of transactions will allow NYISO to utilize the immense hydro storage