Wind Plant Modeling and Interconnection
In order to keep the electricity grid stable and the lights on, the power system relies on certain responses from its generating fleet. The response assists in stabilizing the electrical frequency and avoiding the shedding of load. Currently, these responses are very rarely provided by wind turbines. This project evaluates the potential for wind turbines and wind power plants to provide these services and assist the grid during critical times.
Active Power Control from Wind Power
Active Power Control from Wind Power is two-year project that will involve power system simulation studies determining the economic benefit, the impact on steady-state power system operations, as well as the transient response of the system with different types of active power control contributions from wind power.
NREL's Wind Systems Integration group have teamed up with the Electric Power Research Institute, the Colorado School of Mines, and other industry members to research the potential of wind power turbines and wind power plants to provide active power control to the grid (also known as real power or frequency control).
The project will perform simulations and actual field tests on large wind turbines at the National Wind Technology Center, evaluating their responses and providing related analysis to stakeholders. In particular the project will evaluate the following types of control:
Inertial Response
Inertial response is immediate response to a disturbance based on a frequency deviation. This response is currently given by synchronous machines that immediately give kinetic energy to the grid by slowing down the rotation of the machines. The tests will analyze how wind power can extract the inertia it has to provide immediate energy to help reduce the rate of change of the frequency deviation.
Primary Frequency Response
Primary frequency response is the response following inertial response that increases the output of generators to balance the generation and load. This response, also called primary control, frequency responsive reserve, and governor droop, is typically given by conventional generators with governor control that adjusts the output based on the frequency deviation and its governor droop characteristic. The tests will analyze how wind power can provide energy in this time frame to assist in arresting the frequency deviation, raising the frequency nadir for a given loss of supply, and stabilizing the system frequency at different time points following the disturbance.
Automatic Generation Control
Automatic generation control, or AGC, is used during both emergency events and normal conditions. Automatic generation control, also called load frequency control and secondary control, is a response slower than primary frequency control that assists in returning the frequency back to its nominal set point, which in North America is 60 Hz. It also assists in reducing the area control error, or ACE, during all times to ensure that both frequency and interchange energy schedules between regions is kept to schedule. The tests will analyze how wind power can provide this AGC to stabilize frequency and reduce ACE.
Active Power Control from Wind Power Workshop 
NREL and the Electric Power Research Institute conducted a workshop in January 2011. The purpose of the workshop was to discuss the research needs and state of the art of providing active power control from wind turbines and wind plants. Workshop proceedings are available.
Phase 1 Status
The team has put together a status update report on work that has been done since the January 2011 workshop as well as an update on future plans for the project. We invite the workshop participants as well as other industry stakeholders to review the document and send any feedback to Erik Ela.
More Information
Active Power Control Testing at the U.S. National Wind Technology Center. Ela, E. Presented at the Wind Energy Systems Workshop, Riso DTU, Roskilde, Denmark. November 2010.
