Out of the wall in the US we get 120v @ 60Hz (elsewhere is 220v to 240v @ 50Hz). If the load becomes too high, the frequency starts to drop.
Inductive (motors and such) loads do not fare well when the frequency drops which can cause serious damage. Capacitive or Resistive loads can handle a bit more fluxation, but the whole system is built around the idea that voltage and frequency are fixed. Fluxations can cause grid failures, brownouts, or damage to consumer electronics.
AFAIK, that is precisely what is happening here. The batteries are dumping energy into the grid to bring the frequency back up to where it should be. What's cool is that Tesla was not contracted to do, but did anyway. Good PR.
Inductive (motors and such) loads do not fare well when the frequency drops which can cause serious damage. Capacitive or Resistive loads can handle a bit more fluxation, but the whole system is built around the idea that voltage and frequency are fixed. Fluxations can cause grid failures, brownouts, or damage to consumer electronics.
AFAIK, that is precisely what is happening here. The batteries are dumping energy into the grid to bring the frequency back up to where it should be. What's cool is that Tesla was not contracted to do, but did anyway. Good PR.