Grid-connected photovoltaic power system Solar energy gathered by photovoltaic solar panels, intended for delivery to a power grid, must be conditioned, or processed for use, by a grid-connected inverter. Fundamentally, an inverter changes the DC input voltage from the PV to AC voltage for the grid. This inverter sits between the solar array and the grid, draws energy from each, and may be a large stand-alone unit or may be a collection of small inverters, each physically attached to individual solar panels. See AC Module. The inverter must monitor grid voltage, waveform, and frequency. One reason for monitoring is if the grid is dead
Injective module group Q/Z and the circle group are also injective Z-modules. The factor group Z/"nZ for "n" > 1 is injective as a Z/"nZ-module, but "not" injective as an abelian group. More generally, for any integral domain "R" with field of fractions "K", the "R"-module "K" is an injective "R"-module, and indeed the smallest injective "R"-module containing "R". For any Dedekind domain, the quotient module "K"/"R" is also injective, and its indecomposable summands are the localizations formula_1 for the nonzero prime ideals formula_2. The zero ideal is also prime and corresponds to the injective "K". In this way there is a