We have always wondered if RE plants can provide frequency and voltage support to the grid, First Solar is making the case:
"First Solar slightly curtailed power output at a 300-megawatt solar farm in California, enabled its array of inverters, and plugged into CAISO’s system. It then orchestrated the plant’s output to follow CAISO’s automatic generation control (AGC) signals, respond to its frequency regulation commands, and use inverters for voltage regulation, power factor regulation and reactive power control."
For more details see https://www.greentechmedia.com/articles/read/PV-Plants-Can-Rival-Frequen...