Grid frequency control

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Imbalances between supply and demand for electricity might produce variations in the grid frequency.

Over-frequency can be corrected by limiting the electricity supplied to the grid, thus leading to a reduction of the grid frequency back to its normal value. Some grid codes require such active power reduction to act automatically, by reducing the output power of generation proportionally of the deviation from the nominal frequency.

Under-frequency is however a more complex problem to solve for renewable energy power, as these facilities operate normally at the maximum power output resulting from the resource locally available. Thus, an increase in the production in order to raise the frequency in the case that it becomes too low is not possible, or otherwise power plants would have to be operated under its maximum capabilities, thus wasting energy.

However, grid operation requirements are starting to focus also on this need, which can only be carried out effectively by using short term electricity storage solutions. Several storage systems are being developed (batteries, capacitors, flywheels, compressed air, etc.), but the key element for its effectiveness is the management of such devices regarding power exchange with the grid and integration in its control system. Again, power electronics provides the most efficient way to deal with such requirements.