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
Length of a module precisely the simple modules. For every finite-dimensional vector space (viewed as a module over the base field), the length and the dimension coincide. The length of the cyclic group Z/"n"Z (viewed as a module over the integers Z) is equal to the number of prime factors of "n", with multiple prime factors counted multiple times. A module "M" has finite length if and only if it is both Artinian and Noetherian. (cf. Hopkins' theorem) If "M" has finite length and "N" is a submodule of "M", then "N" has finite length as well, and we have length("N") ≤ length("M"). Furthermore,