Can anyone explain how solar power gets injected back into the incoming mains supply ?In the UK, the normal 'simple' inverter has an output power limited to ~3.6KW @220v/240v (16A) without the need for heavy paperwork approval. The incoming mains mus have a very low impedance to how does the inverter push power back into the grid ? I guess there must be a similar situation in the USA...
mandag den 10. oktober 2022 kl. 16.23.36 UTC+2 skrev TTman:
just like you would charge a battery, which is also very low impedance. Provide a voltage slightly higher than the battery
Not really.. I'm ex electronics engineer but not mains stuff. microwatt
433MHz stuff. I get the basics, PLL to the incoming mains and as Lasse says- a slightly higher output voltage will result in export to grid. Thanks, both.
Trace engineering has some patents on their stuff. Once they sync to the line, they wiggle their frequency to stay synced and verify the mains freq is still present.
Cheers
The Trace SW4024, SW5548 etc was one of the first inverters to sell back to the grid. Voltage source actually. The wiggle you mention is for making sure that the grid was still there. Anti-Islanding they call it. Solar inverters must also do something similar. I don't think there were any patents issues on the SW inverter(s) though... I know there was an application at one time but don't remember how far that got. It was something that could not be patented. I worked there for several years unitl just after the merge with Xantrex when we started OutBack power.
They typical solar photovoltatic to grid tie only inverters are typically (were) a current source.
Think of a regluar power factor corrected power supply where it draws a current that is shaped (referrenced) to the grid voltage....
One of those PV grid tied inverters would do the same thing except the power flowed the other way.
Yes, trying to raise the grid voltage sells back and charging a battery for instance, draws current from the grid.
Nowadays the utilities want grid tied or grid interactive inverters to be able to provide "ride through" for a few seconds when the grid is browning out or to clean up the grid somewhat by selling back at a power factor less than 1.0
boB
The patents you refer to might be from Trace Technologies which was acquired during the Xantrex involvement with Trace Engineering ?
TT did big wind turbine inverter electronics.
boB
I think the patent may have been for the transformer setup they used. To get that quasi sinewave.
Cheers
It's more or less the reverse from an induction motor.
Current is fed back into the grid with a synchronized inverter, with current mode control to apply a sinusoidal current.
In an induction generator frequency is a little higher than the grid, that pushes current back. For electronic control, it controls the current, so it can be synchronous
Some info here:
basically the inverter output is a current source, (not a voltage source), so it's not bothered by the low load impedance.
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