Nowadays, I see that photovoltaic systems have Low-voltage-ride-through capabilities. So in case of a fault, when the voltage is decreased, they remain connected to the grid and provide reactive power in order to support the voltage. In order to do so, they decrease the active power that they inject.
Low voltage distribution grids are mostly resistive. So, voltage regulation is more effective by injecting active power rather than reactive (R/X >1) So, why we inject reactive power?