Grid-tie inverter

Grid-tie inverters are used between local electrical power generators: solar panel, wind turbine, hydro-electric, and the grid.

In this case the electricity company would pay for the 100 kilowatt hours balance of power fed back into the grid.

[3] Instead of converting direct current directly into AC suitable for the grid, high-frequency transformers types use a computer process to convert the power to a high-frequency and then back to DC and then to the final AC output voltage suitable for the grid.

But transformerless inverters have been slow to enter the US market because of concerns that transformerless inverters, which do not have galvanic isolation between the DC side and grid, could inject dangerous DC voltages and currents into the grid under fault conditions.

Amendments to VDE 0126-1-1 and IEC 6210 define the design and procedures needed for such systems: primarily, ground current measurement and DC to grid isolation tests.