Use of Wind Turbine Kinetic Energy to Supply Transmission Level Services

Abstract

This paper discusses the broad use of rotational kinetic energy stored in wind turbine rotors to supply services to the electrical power grid. The grid services are discussed in terms of zero-net-energy, which do not require a reduction in power output via pitch control (spill), but neither do they preclude doing so. The services discussed include zero-net-energy regulation, transient and small signal stability, and other frequency management services. The delivery of this energy requires a trade-off between the frequency and amplitude of power modulation and is limited, in some cases, by equipment ratings and the unresearched long-term mechanical effects on the turbine. As wind displaces synchronous generation, the grid's inertial storage is being reduced, but the amount of accessible kinetic energy in a wind turbine at rated speed is approximately 6 times greater than that of a generator with only a 0.12% loss in efficiency and 75 times greater at 10% loss. The potential flexibility of the wind's kinetic storage is also high. However, the true cost of providing grid services using wind turbines, which includes a potential increase in operations and maintenance costs, have not been compared to the value of the services themselves.

Review of wake management techniques for wind turbines

“…These services include active power control (APC) in which the power production of a wind farm is actively managed to either hold some power in reserve by operating below its rated power or automatic generation control (AGC) in which a wind farm is asked to follow a reference power signal 8,9 . While wind farms cannot provide inertia to the grid automatically as synchronous generators can, they can be quickly actuated to adjust their production levels, 10 and they can store kinetic energy in their rotors for quick release to aid in frequency regulation 10–13 . Finally, with advances in power electronics, wind turbines are now also able to provide reactive power control to maintain system voltage at least locally 14–16 .…”

“…While it is necessary to consider the results more cautiously due to the use of wake models, which may not capture the effects of changing thrust and/or TSR , as opposed to the high‐fidelity CFD methods used above, other studies have optimized wind farms for frequency regulation, 11–13,46,51,58,73 reducing power gradients, 80 and providing reactive power dispatch 16 using some form of AIC. It is likely that all of these capabilities have great potential with AIC, but future work using high‐fidelity methods that accurately represent wind turbine wake dynamics and their effects on power production are needed.…”

WGRID-49 GMLC Project Report: Understanding the Role of Short-Term Energy Storage and Large Motor Loads for Active Power Controls by Wind Power

“…We consider a WPP composed of equal turbines. The harvested power by an -th turbine, = 1, … , , is [35]:…”