With the current structure of the electrical system, this actually causes problems in isolated markets. In Hawaii, there are sections of the grid that are oversupplying 250% of what it should take and causing problems with the interconnect getting power from regions that it wasn't built to handle.

https://www.utilitydive.com/news/an-embarrassment-of-riches-...

100% renewable is great if it can be sustained. But if there is too much power put into the grid, that because an issue. Also it means that other systems need to shut down (its really hard to shut down the distributed solar on rooftops of residential units).

Its really hard to curtail an oil plant - they don't shut down or power up quickly. And neither wind nor solar can provide the base power generation necessary in Hawaii for extended night use currently (it needs a sizable power storage system).

Load shifting is something that needs to be looked into more (and that is what Tesla is doing with their battery packs).

https://electronics.stackexchange.com/q/117437 is a good read.