Wind energy technology can support and enhance the reliability of the U.S. power grid by controlling the active power output being placed onto the system, finds a new study from the National Renewable Energy Laboratory (NREL). The rest of the power system's resources have traditionally been adjusted around wind to support a reliable and efficient system; however, NREL says the research that led to its report challenges that concept.
The national lab conducted the study, "Active Power Controls from Wind Power: Bridging the Gaps," with partners from the Electric Power Research Institute and University of Colorado.
The report also finds that it often could be economically beneficial to provide active power control, and potentially damaging loads on turbines from providing this control is negligible. NREL says active power control helps balance load with generation at various times, avoiding erroneous power flows, involuntary load shedding, machine damage and the risk of potential blackouts.
"Utilities and independent system operators are all seeking strategies to better integrate wind and other variable generation into their electric systems," says NREL Analyst Erik Ela. "Few have considered using wind power to support power system reliability."
The study included a number of different power system simulations, control simulations, and field tests using turbines at NREL's National Wind Technology Center (NWTC). The lab says the study developed proposals for new ancillary services designs in U.S. wholesale electricity markets, studied how wind power affects system frequency in the western U.S. with and without active power control, and tested the use of active power control at the NWTC to better understand the performance and structural impacts on wind turbines when providing active power control to the electric system.
"Although many of the control strategies have been proven technically feasible and are used in many regions of the world, only a limited number of wind turbines in the United States are currently providing active power control," Ela explains. "The reason is that the stakeholders - system operators, manufacturers, regulators and the plant owners - all have different goals and perspectives."
According to NREL, wind is one of the fastest-growing sources of power generation - supplying up to 20% of electricity in many areas of the world. In some regions of the U.S., wind sometimes provides more than 50% of the electric power. However, NREL says the challenge with integrating high concentrations of wind power into electric systems is that it is a variable, uncertain resource, commonly considered "non-dispatchable."
The forms of active power control considered in this study are synthetic inertial control, primary frequency control and automatic generation control regulation. For wind power to provide active power control services, NREL says three things must happen:
1) The wind power response needs to improve power system reliability, not impair it.
2) It must be economically viable for wind power plants as well as electricity consumers. Because power plants may incur additional capital costs for the controls and reduce the amount of energy it sells to the market, there must be an incentive to provide the service.
3) Active power control should not have negative impacts on the turbine loading or induce structural damage that could reduce the life of the turbine.
NREL says the comprehensive study analyzed time frames ranging from milliseconds to the lifetime of wind turbines, spatial scopes ranging from turbine components to entire regions and study types ranging from economics to power systems engineering to control design.
"The study's key takeaway is that wind power can act in an equal or superior manner to conventional generation when providing active power control, supporting the system frequency response and improving reliability," Ela concludes.
SOURCE: The National Renewable Energy Laboratory (NREL)