How do solar microinverters prevent back-powering an electrical grid during a power company power failure?
菲薄是什么意思
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\$\begingroup\$ An emergency power-capable inverter (a hybrid inverter) enables the household to be supplied with power even in the event of a power failure by switching to a power storage unit or providing a basic emergency power supply when necessary. It differs from conventional inverters, which shut down in the event of grid disturbances, and is an important component of a self-sufficient solar power system. \$\endgroup\$– MikeCommented yesterday
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3 Answers
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Microinverters typically will shut down when they sense that the main power grid is down. This is known as anti-islanding protection and is meant to protect power grid workers from working on a section that they think is down, but is actually still being powered by an inverter.
Sensing of the grid state can be passive, detecting things like voltage, frequency or zero-crossing, or it can be active, applying a signal to the grid and seeing if it reacts as expected.
On loss of grid the inverter should shut of rapidly, within a few seconds. On sensing the grid coming back there should be a delay of a minute or two before reconnecting the inverter to try to make sure the grid is stable first.
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They sense the frequency. If it disappears, in means that the grid is gone.
However, if the load includes an induction motor, it will keep on spinning and creating the line frequency. However, the sign of the slip will change: the frequency will drop. If the frequency starts dropping, the inverter knows the grid is gone.
Once they do sense that the grid is gone, they shut down their output.
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As of 2025, the other answers are correct. Inverters sense the grid somehow and refuse to output power if it's missing.
There is a move to give the option for future inverters to be able to power an unpowered grid, to make them more versatile. It's only a software change. It remains to be seen how that facility will be presented to the user and controlled.
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\$\begingroup\$ Wouldn't supplying power to an unpowered grid be a significant safety issue? The answer by @GodJihyo touches on this. \$\endgroup\$ Commented 14 hours ago
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\$\begingroup\$ @MichaelRichardson Absolutely, which it why it remains to be seen how that facility will be presented to the user and controlled. \$\endgroup\$– Neil_UKCommented 12 hours ago
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\$\begingroup\$ Powering an unpowered grid won't work. When the power comes back again, the phase of the inverter is not in sync with the phase of the grid. They will fight each other. The way to allow power in an unpowered grid is with battery inverter/chargers like Victron MultiPlus. You can connect inverters to its output, and if done so, the output maintains AC voltage, and the inverter sees that. When the power goes back up again, the MultiPlus will slowly start to sync its output to the grid, and when that's done, the MultiPlus will give you the grid voltage back again. \$\endgroup\$– juhistCommented 14 mins ago