An inverter converts direct current (DC) into alternating current (AC) by mechanical
or electronic means and makes renewable resources and energy-storage systems
utility interactive. Inverters are basic components on most small and large energy
systems that convert low-voltage DC power generated from a renewable energy
source into higher-voltage AC power required for many residential, commercial, and
industrial applications. Grid-tied inverters are required in energy systems that
produce or store electric energy in DC form and transfer that energy to or from an
AC power system. Typical energy systems include solar photovoltaics (PV), wind
turbines, batteries, and fuel cells. Grid-tied inverters were considered unreliable
when they were first commercially introduced in the early 1980s. Their problems
were attributed to the lack of quality control that comes from mass production.