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
Localization of a module of flatness in algebraic geometry, saying in particular that the inclusion of the open set Spec("S""R") into Spec("R") (see spectrum of a ring) is a flat morphism. In terms of localization of modules, one can define quasi-coherent sheaves and coherent sheaves on locally ringed spaces. In algebraic geometry, the quasi-coherent "O"-modules for schemes "X" are those that are locally modelled on sheaves on Spec("R") of localizations of any "R"-module "M". A coherent "O"-module is such a sheaf, locally modelled on a finitely-presented module over "R". Any textbook on commutative algebra covers this topic, such as: Localization of a module In