Solar panels have no problem if nothing consumes the power they can produce.

Wind turbines can be feathered and the turbine break engaged until they stop, at which point they're not generating anything.

So negative energy prices are not really a technical problem of renewables, rather they're due to the way the decision of "who stops their generation" being left to market systems - rather than there being some kind of centralized control, possibly with agreements in place, that decides which generators are stopped first when there is excess generation, market prices just float as offer and demand float and individual suppliers are left to individually decide if it's worth it for them to generate for a given price or not and thus if they should reduce or stop their generation.

There are delays and inertia in the whole process of signalling demand/supply balance via market prices, so there result is that the price can overshot and undershot, the latter being sometimes all the way down to negative prices.