A photovoltaic (PV) inverter is an inverter that converts the variable DC voltage generated by photovoltaic solar panels into AC power at the grid frequency. This AC power can be fed back into commercial transmission systems or supplied to off-grid systems. PV inverters are an important component of the balance of systems (BOS) in a photovoltaic array system and can be used in conjunction with general AC-powered equipment.
Photovoltaic inverters can be divided into the following three categories:
Stand-alone inverters: Used in stand-alone systems, where the photovoltaic array charges the batteries, and the inverter uses the batteries' DC voltage as its energy source. Many stand-alone inverters also integrate battery chargers, allowing the batteries to be charged using AC power. Generally, these inverters are not connected to the grid, therefore they do not require islanding protection.
Grid-tie inverters: The output voltage of these inverters can be fed back to commercial AC power, therefore the output sine wave needs to be identical to the phase, frequency, and voltage of the power supply. Grid-tie inverters have safety features; if not connected to a power source, they will automatically shut off the output. If the grid power supply trips, the grid-tie inverter does not have a backup power supply function.
Battery backup inverters are a special type of inverter that uses batteries as its power source, charging them with an integrated battery charger. Excess power is fed back to the AC power source. These inverters can provide AC power to designated loads during grid power outages, therefore requiring islanding protection.
