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
Galois module of "v" to "L", let "I" denote its inertia group. A Galois module ρ : "G" → Aut("V") is said to be unramified if ρ("I") = {1}. In classical algebraic number theory, let "L" be a Galois extension of a field "K", and let "G" be the corresponding Galois group. Then the ring "O" of algebraic integers of "L" can be considered as an "O"["G"]-module, and one can ask what its structure is. This is an arithmetic question, in that by the normal basis theorem one knows that "L" is a free "K"["G"]-module of rank 1. If the same is