A solar inverter or PV inverter is a critical component in a Photovoltaic system. It performs the conversion of the variable DC output of the Photovoltaic (PV) modulesinto a utility frequency AC current that can be fed into the commercial electrical gridor used by a local, off-grid electrical network. An inverter allows use of ordinary mains-operated appliances on a direct current system. Solar inverters have special functions adapted for use with PV arrays, including maximum power point trackingand anti-islanding protection.
Solar inverters may be classified into three broad types:
- tand-alone inverters, used in isolated systems where the inverter draws its DC energy from batteries charged by photovoltaic arrays. Many stand-alone inverters also incorporate integralbattery chargers to replenish the battery from an AC source, when available. Normally these do not interface in any way with the utility grid, and as such, are not required to have anti-islanding protection.
- Grid tie inverters, which match phase with a utility-supplied sine wave. Grid-tie inverters are designed to shut down automatically upon loss of utility supply, for safety reasons. They do not provide backup power during utility outages.
- Battery backup inverters, are special inverters which are designed to draw energy from a battery, manage the battery charge via an onboard charger, and export excess energy to the utility grid. These inverters are capable of supplying AC energy to selected loads during a utility outage, and are required to have anti-islanding protection.
Solar inverters may fail due to transients from the grid or the PV panel, component aging and operation beyond the designed limits.