Grid Connected Inverters

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System layout for a grid-connected inverter solar installationAn inverter that produces AC power with the same sine wave and quality as your utility company can "export" power to the utility just like their own turbines. This was unthinkable a decade ago but today the increasing demand for clean, renewable energy and pressure from environmental and industry advocates has loosened the utilities' hold.

There are still some parts of North America which are slow in making the inevitable change, though some like California, which experiences frequent blackouts, smog and high energy costs, are now ready for politicians to act. Today, anyone in that state can install PV panels on their roof and have them connected to a grid-interconnected inverter for great savings on their electricity bill. The state is even ready to give incentive payments to encourage this to happen.

The graphic shows a simple and effective grid-connected system which allows a renewable source to supply energy to the grid. Here, electrical power normally flows from the grid, through the utility meter to the PV panels and the home's electrical loads. Most homes are set up with this import or purchase of power. Power usage is recorded on the meter.

With a renewable energy system, the inverter synchronizes its sine wave to that of the grid. The inverter produces a higher-voltage waveform than the utility and pushes power out to the utility. The utility tracks the energy received on another electronic counter and billing reflects the amount of power imported and exported by your house. Newer "smart meters" allow such data to be sent from your home meter directly to the grid's central office via wireless broadband, radio, cellular phone networks or other similar communication methods.

For safety purposes, the internal electronics of the inverter perform tests on the electrical system to confirm the utility connection's tolerance. Any disturbance such as lightning, blackout or brownout will cause the inverter to shut down immediately and wait for a few minutes before switching on again, even after grid power returns.