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
Generating set of a module minimal if no proper subset of the set generates the module. If "R" is a field, then it is the same thing as a basis. Unless the module is finitely-generated, there may exist no minimal generating set. The cardinality of a minimal generating set need not be an invariant of the module; Z is generated as a principal ideal by 1, but it is also generated by, say, a minimal generating set }. What is uniquely determined by a module is the infimum of the numbers of the generators of the module. Let "R" be a local ring with maximal