Do energy storage systems really improve the quality of the energy?
The distortion added by an inverter can be mitigated to whatever arbitrary standard is needed. Is 10% total harmonic distortion (THD) acceptable? That is probably easy to achieve. But if 1% THD is needed, then I am sure that can be achieved also. It is just a matter of balancing cost vs power quality etc.
But I believe most of the problems on the power line are caused by the loads, not the generators/inverters. So having inverters distributed widely should improve the power quality for most people because the disturbances caused by the loads can't propagate as far on the line. They will be corrected or compensated at the nearest generation source whether it is an inverter or something else.
The one thing about inverters is that some thought has to be given to how they interact with the other generators on the grid. If demand drops suddenly, the inverters need to scale back their output because the big generators can't adjust their output too quickly. I believe what this means is that the inverters must &quot;throttle back&quot; when the voltage and frequency increase, and increase output when the grid voltage and frequency slow down. This should help keep everything stable.