The produced energy can be used to power a local load (off-grid systems) or it can be fed into the public power-grid (grid-connected systems). As the PV generator output is direct DC and most loads and public grids generally accept only AC, PV inverters are used to perform the necessary DC-AC conversion. As the current and voltage output of a PV generator are not constant, the inverter must also adjust to the changes at its input circuit so that the maximum possible power is drawn from the generator. By way of an example, the amount of light available naturally contributes to the PV cells' current output, whereas the voltage output is inversely affected by the cell temperature. Between the PV panels and the AC grid are the so-called balance-of-system (BOS) components. These include the inverter, the interconnecting cables, wires, over-current and surge protection, earthing equipment and a means for switching and disconnecting different parts of the circuit. For example, the international standard IEC 60364-7-712 requires a means for disconnecting the inverter from both sides. Moreover, the standard specifically demands a switch disconnector to be provided on the DC side of the PV inverter. This allows the disconnection and reliable isolation of the inverter from all DC sources. Additional switch equipment can be used for disconnecting parts of the PV array, for system earthing or for switching possible energy-storage circuits.
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