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NREL and EPRI Actively Embrace Active Power Control Systems for Wind Power

December 2, 2013

The Second Workshop on Active Power Control (APC) cohosted by the National Renewable Energy Laboratory (NREL) and the Electric Power Research Institute (EPRI) in Broomfield, Colorado, last May drew more than 60 industry experts from around the world to participate in a comprehensive discussion about the need for and impacts of active power controls from wind plants.

Various forms of active power control can help stabilize the grid by enabling generating sources to increase or decrease power output to meet the constantly fluctuating needs of meeting the load demand and avoid events that can cause brownouts and power failures. The three forms of active power control discussed during the workshop were inertial control, primary frequency control, and automatic generation control. These forms all provide active power output adjustments to help support the generation and load balance at different timescales. Traditional thermal and hydropower generators provide this control, but until recently, active power control was not considered for wind generators.

Although there are currently a limited number of wind turbines providing active power control in the United States, with the rapid growth of wind energy, the industry is now considering the benefits of allowing the provision of these ancillary services from wind. In 2012, wind power was the largest source of new electric-generating capacity, contributing 43% of the total additions in the United States. By the end of the year, wind power provided more than 12% of the total electricity generation in nine states (with three of these states above 20%) and meets roughly 4.4% of total U.S. electricity demand in 2013.

For the past 3 years, NREL and EPRI have been working together to conduct research on the benefits and impacts of active power control from wind. NREL published several papers on its work to develop a control system at the individual turbine level that is capable of de-rating or actively curtailing a turbine to follow a power schedule and track de-rating commands to assist in grid frequency regulation. The system can also provide a primary frequency response to help recover grid frequency during a frequency event. In addition, the team is in the process of publishing a paper on a technical market design for primary frequency response, and another on how the frequency response of the Western Interconnection changes with wind providing active power control.