Tests by the California Independent System Operator (CAISO) have demonstrated that a large utility-scale wind power plant can provide important ancillary services to the electric grid as effectively as conventional resources, like gas-fired peaking plants.
During several days in 2019, CAISO, Avangrid Renewables, National Renewable Energy Laboratory, and General Electric conducted a series of tests at Avangrid Renewables’ Tule Wind Farm, located in CAISO’s balancing authority in the McCain Valley, east of San Diego. The plant currently has a maximum capacity of 131.1 MW and participates in CAISO’s energy market.
Various tests were designed to determine whether a WPP with an advanced plant-level controller with unique operating characteristics can enhance system reliability by providing essential reliability services to:
• Ramp up/down at specified ramp rates
• Respond to 4-second control signals from CAISO’s energy management system
• Control scheduled voltage when the plant’s output varies from zero to full output
• Provide fast frequency control within the inertia response time frame
• Provide frequency regulation similar to the governor actions of a conventional resource on governor control
• Respond to frequency response deviations for low- as well as high-frequency events.
Results were positive on all counts.
The objective was to incentivize increased integration of renewable generation, thereby supporting not only the State of California’s carbon reduction goals but also international efforts to decarbonize the electric power industry.
Similar results were found from a 2018 test on an inverter-controlled solar power plant.
The report, dated March 11, comments that most renewable generation around the country is built to fulfill a renewable portfolio standard (RPS) and is incentivized to maximize energy production. However, providing critical grid services might require renewable resources to operate below their maximum capabilities. On the other hand, it adds, wind resources could offer regulation-down service at times of oversupply; and when curtailed for economic reasons, wind resources could offer regulation-up services. When wind production is curtailed, available headroom could be used to provide other essential grid services, such as frequency response for low-frequency events and ancillary services such as spinning and non-spinning reserves. Policymakers should consider ways to valorize such projects’ potential ancillary functions, it suggests.