The ability of wind power to deliver FFR, part 2

Wind power has a good ability and capacity to contribute to rapid frequency control to the electricity grid. Part 1 of this project focused on investigating wind power's possible and cost-effective contribution to the Fast Frequency Reserve (FFR) system service. It means maintaining a power reserve to quickly support the grid with, if the frequency drops below a certain level (around 49.7 Hz).

By increasing the rotor speed in wind speeds below rated wind, an additional rotational energy is generated, which quickly can be converted into additional power (FFR) to the grid, if the frequency should drop for any reason. With a coordinated and active control of the wind turbines, it is theoretically possible to handle the worst possible failure case (an FFR capacity of 280 MW) with wind power alone. The cost in lost energy production would then be approximately one percent (1%), as a result of operating at a higher rotor speed than optimal speed in low winds.

This part 2 of the project, funded by the Swedish Energy Agency, deepens the study and focuses on the economic consequences. A loss of production costs different depending on when the loss occurs. Therefore, it is important to go a step further and calculate whether or not it is financially beneficial to offer FFR for the hours to come. Therefore, the operation of wind turbines at different locations has been studied and compared hour by hour based on which product (energy or FFR) gives the best revenue.

To carry out the study, the wind speed has been estimated, hour by hour. First aactual wind measurements from 2016 and 2017 have been downloaded from twelve (12) locations around Sweden, three (3) in each SE area. Second, the wind speed has been calculated based on actual production data in each SE area. The result of a comparison can be seen in the graph below, which shows October 2017, where the wind speed has been measured at a height of 150 meters.

By this method, the wind speed for recent years has been calculated, when price information is available for both energy and purchased FFR.

T0 and T1 are two generic wind turbines IEA-3.4-130-RWT. By simulating different ways of running the turbines, the compensation for producing energy alone has been compared to the compensation for producing both energy and FFR. T0 runs in the traditional way to deliver maximum energy production. T1 runs at increased RPM in low winds, provided FFR is requested. T1 can thereby also receive income from FFR.

An example of how the revenue is distributed between the different operating modes is shown below, during two summer weeks in 2021. In this period, the FFR compensation far exceeds the compensation from the energy production, thereby compensating for the lower production.

By summing up the total revenues from the respective turbines T0 and T1 over the entire year, it can be shown whether FFR can generate additional revenues. Delivered FFR is a standby service, i.e. the turbine is ready to support the grid if the frequency would drop below 49.5 Hz. This does not mean that the extra power is actually executed, as such frequency drops are very rare.

The results show that FFR would generate an extra income of between 300 and 500 kSEK per year in 2021 and 2022, even though energy production decreased by approximately 1 percent. During 2023, however, SVK has procured significantly smaller volumes of FFR, also at lower marginal prices. Therefore, the corresponding earnings are significantly lower for this year.

Conclusion: If a wind turbine were to offer FFR, the income from FFR compensates for the loss of production that the higher speed entails.