Without having studied the Norwegian grid, the Swedish one that it is connected to also experience negative prices som nights when there’s a lot of wind and we generate some 10 GW of wind power. Coupled with the nuclear plants in Sweden that still are online and we pretty much have an issue with too much being generated… Then again things freaked out in the opposite direction when two of the plants went a offline, the wind was basically zero and we had freezing temps all over the country.