Frequency Regulation

For small power systems, for example where there are only one or a few generators, significant load increases will cause the frequency to slow and the voltage to droop.  Similarly, the frequency will increase when there is loss of load.  If the frequency varies by too large an amount, there are system wide impacts as motors speed up or slow down, etc.  Of particular significance is the case where the frequency and voltage decrease.  Under these conditions, electric motors tend to demand greater current to maintain power output and thus worsen the effect.

Large power systems have frequency control requirements that set limits at which the utility or the generator must carry out some action.  An electricity storage device can supplement the power system while total generation is increased either by the addition of generators or while the power output of online generation is increased.