What is the benefits of a hybrid power system as supposed to just a backup power system of a grid-tied solar system?

Grid-tied solar systems depend on a grid being present for it to work. If there is no grid for example during load shedding the solar system also stops working. Having a backup power system in place, allows the solar system to continue working, even if there is a grid power failure. This is achieved by the backup power inverter simulating a local grid for the grid-tied inverter.