To add to this, when too much energy is fed into the grid, the net frequency increases slightly. Thus, the control variable is net frequency. There is lots of r

To add to this, when too much energy is fed into the grid, the net frequency increases slightly. Thus, the control variable is net frequency. There is lots of research on this problem. When the net frequency increases so does the rotating speed of all turbines. The inertia of those turbines is one way how excess energy is buffered.