Grid-Tie Inverters

https://www.raisunpower.com/products/grid-tie-inverters/

The grid-connected inverter is a special inverter. In addition to converting DC power into AC power, the output AC power can be synchronized with the frequency and phase of the mains power, so the output AC power can be returned to the mains. Grid-connected inverters are commonly used in applications where some DC voltage source (such as a solar panel or a small wind turbine) is connected to the grid.