Negative prices (i.e. excess of energy), and really high ones (lack of it) rarely happen. When they do, there is ancillary services that take over (which there is plenty in Europe).

Actually, the share of intermittent renewable energy is negligible in France. Let's worry about that later, as there will be plenty of choices (demand response, PHES, and even tesla, which is building AS plants without us noticing (Belgium))