Generally the voltage is a bad signal for grid load, it varies from too much from one part of the grid to another. It makes to have a safety cut-out if it goes

Generally the voltage is a bad signal for grid load, it varies from too much from one part of the grid to another. It makes to have a safety cut-out if it goes too far out of bounds, but if it trips the grid is likely already quite over-supplied and other problems have happened first. The main signal that's generally used to evaluate grid load is instead the frequency: it's the same everywhere on a synchronous grid, and because of inertial generation it will increase when there's more supply than demand, and decrease when there's more demand than supply, and that's what grid operators monitor to adjust the supply to meet demand. Though it's worth noting, there's nothing that fundamentally stops an inverter from emulating an intertial generator: solar panel inverters can smoothly output anywhere from 0 to 100% of the power available from the solar panel (the remaining energy just gets dissipated as heat inside the panel, which doesn't harm it since it's at most an increase equal to the efficiency of the panel in the first place). A grid which has enough spare capacity in solar panels could operate stably off of them alone, while there's enough margin, if enough of the inverters were doing this emulation (OK, it would be slightly more complicated, you would still need some central control of generation to keep power flows balanced in the grid) But in general home solar inverters don't implement this, there would still need to be some standardisation on how the grid controls them, and you probably still want some battery storage anyway as they can do it much more efficiently (solar inverters doing this emulation would necessarily not be running near 100% output), and it may be cheaper and easier to mostly delegate it to them.