Surely when the price of power turns negative, you just start to disconnect panels from the inverters at the low-voltage side? The voltage remains, but no current flows, and no power is generated. If switching huge DC currents is the issue, this disconnection can be pushed down towards the panel level; relays/contactors would do fine, and you can dial capacity up and down by connecting or disconnecting a greater or lesser area of panels.

Is there some electrical engineering reason this cannot be done?