There is a form of “robustness” inherent in AC power generated by rotating electro-magnetic fields (spinning generators). Those magnetic fields are a form of very short-term power storage that can fluctuate in reaction to changing loads. This is one form of reactive power or VAR (Volts-Amps-Reactive). VAR provides a level of stability to the power and adds a component of muscle to the power which enhances its transportability across distances.
Virtually all energy experts recognize the need for cheap and efficient energy storage systems. It has become obvious that solar, wind, or any other form of intermittent power generation cannot serve base load requirements or provide reliable peak shaving without storage, but until very recently, the costs have simply been too high.