Solar inverters...

T

TTman

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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...

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On Monday, October 10, 2022 at 10:23:36 AM UTC-4, TTman wrote:
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...
Click to expand...

Probably over you head:
https://www.digikey.com/en/articles/synchronizing-small-scale-pv-systems-with-the-grid

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Click to expand...
 
mandag den 10. oktober 2022 kl. 16.23.36 UTC+2 skrev TTman:
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...
Click to expand...

just like you would charge a battery, which is also very low impedance.
Provide a voltage slightly higher than the battery
 
On 10/10/2022 15:49, Fred Bloggs wrote:
On Monday, October 10, 2022 at 10:23:36 AM UTC-4, TTman wrote:
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...

Probably over you head:
https://www.digikey.com/en/articles/synchronizing-small-scale-pv-systems-with-the-grid
Click to expand...
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.


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TTman <kraken.sankey@gmail.com> Wrote in message:r
> 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...-- This email has been checked for viruses by Avast antivirus software.www.avast.com

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
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On Mon, 10 Oct 2022 12:39:21 -0400 (EDT), Martin Rid
<martin_riddle@verison.net> wrote:

TTman <kraken.sankey@gmail.com> Wrote in message:r
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...-- This email has been checked for viruses by Avast antivirus software.www.avast.com

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
Click to expand...

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
 
On Mon, 10 Oct 2022 12:39:21 -0400 (EDT), Martin Rid
<martin_riddle@verison.net> wrote:

TTman <kraken.sankey@gmail.com> Wrote in message:r
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...-- This email has been checked for viruses by Avast antivirus software.www.avast.com

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
Click to expand...

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
 
boB <boB@K7IQ.com> Wrote in message:r
> On Mon, 10 Oct 2022 12:39:21 -0400 (EDT), Martin Rid<martin_riddle@verison.net> wrote:>TTman <kraken.sankey@gmail.com> Wrote in message:r>> 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...-- This email has been checked for viruses by Avast antivirus software.www.avast.com>>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.>>CheersThe patents you refer to might be from Trace Technologies which wasacquired 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
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On Monday, October 10, 2022 at 10:23:36 AM UTC-4, TTman wrote:
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...
Click to expand...

Some practical info here. The industry doesn\'t want people messing with it:
https://solar.smps.us/grid-tie-inverter-schematic.html

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Click to expand...
 
Martin Rid <martin_riddle@verison.net> wrote:

I think the patent may have been for the transformer setup they
used. To get that quasi sinewave.
Click to expand...

That sounds tricky. I thought most AC converters use PWM to generate sine
waves.




--
MRM
 
On 10-10-2022 16:23, TTman wrote:
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...
Click to expand...

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:

https://en.wikipedia.org/wiki/Grid-tie_inverter
 
On 10/10/2022 7:23 AM, TTman wrote:
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
Click to expand...

Isn\'t that a \"standard circuit\" (for you)? I.e., the \"extra paperwork\"
may not relate to a \"maximum injected power per household\" but, rather,
a limit on a single inverter.

Could you, for example, have *two* (independent) inverters feeding back
into the mains (a house around the corner has just such an arrangement)?

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...
Click to expand...
 
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:

On 10-10-2022 16:23, TTman wrote:
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...


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:

https://en.wikipedia.org/wiki/Grid-tie_inverter
Click to expand...

Your comparison with an induction motor is misleading. There is no motor
involved.

Instead, the sine wave conversion is from a PWM inverter. This is purely
electronic, and is used in many applications requiring conversion from DC
to sine wave AC.

A typical application is converting 12V DC from a car battery to 120VAC to
run a small drill. Another is an uninterruptable power supply to provide
power during outages. Another is ultra high DC transmission used in long
distance networks to eliminate the skin effect in conductors that renders
the central portion of the conductor useless, and increases the resistance
of the conductor to AC current.





--
MRM
 
On 2022-10-10, TTman <kraken.sankey@gmail.com> wrote:
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...
Click to expand...

basically the inverter output is a current source, (not a voltage
source), so it\'s not bothered by the low load impedance.

--
Jasen.
 
On 11-10-2022 01:24, Mike Monett VE3BTI wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:

On 10-10-2022 16:23, TTman wrote:
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...


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:

https://en.wikipedia.org/wiki/Grid-tie_inverter

Your comparison with an induction motor is misleading. There is no motor
involved.
Click to expand...

The OP wanted an explanation. The operation of a generator is similar,
that\'s why I brought it up. It\'s all about rotating vectors, does not
matter if it is a motor or an inverter
 
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:

On 11-10-2022 01:24, Mike Monett VE3BTI wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:

On 10-10-2022 16:23, TTman wrote:
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...


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:

https://en.wikipedia.org/wiki/Grid-tie_inverter

Your comparison with an induction motor is misleading. There is no
motor involved.


The OP wanted an explanation. The operation of a generator is similar,
that\'s why I brought it up. It\'s all about rotating vectors, does not
matter if it is a motor or an inverter
Click to expand...

So you know a motor is never used and instead it is an inverter.

Then why did you not say so?



--
MRM
 
On Monday, October 10, 2022 at 6:58:07 PM UTC-4, Don Y wrote:
On 10/10/2022 7:23 AM, TTman wrote:
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
Isn\'t that a \"standard circuit\" (for you)? I.e., the \"extra paperwork\"
may not relate to a \"maximum injected power per household\" but, rather,
a limit on a single inverter.

Could you, for example, have *two* (independent) inverters feeding back
into the mains (a house around the corner has just such an arrangement)?
Click to expand...

Portable parallelable inverter generators do that. They\'re their own microgrid.

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...
Click to expand...
 
On Mon, 10 Oct 2022 22:11:33 -0000 (UTC), Mike Monett VE3BTI
<spamme@not.com> wrote:

Martin Rid <martin_riddle@verison.net> wrote:

I think the patent may have been for the transformer setup they
used. To get that quasi sinewave.

That sounds tricky. I thought most AC converters use PWM to generate sine
waves.
Click to expand...

Nowadays PWM is the way and has been, even before the Trace SW series.
The Dynamote inverter/charger was a HF PWM inverter that pre-dated the
SW4024 etc. from the 1980s. It had high idle power which wasn\'t
good for people going off grid.

The SW with its 3 transformers in series was good because it had LOTS
of surge and was very rugged and has low idle power which was a big
thing back around 1992 or so.

I didn\'t think that patent ever got issued because there was prior
art. There was a chapter in a book from around 1960 titled \"Improving
the Inverter Waveform\" that had that same kind of method except
instead of power MOSFETs, they used a system with thyristors.

boB
 
On Tue, 11 Oct 2022 06:12:32 -0000 (UTC), Jasen Betts
<usenet@revmaps.no-ip.org> wrote:

On 2022-10-10, TTman <kraken.sankey@gmail.com> wrote:
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...

basically the inverter output is a current source, (not a voltage
source), so it\'s not bothered by the low load impedance.
Click to expand...

Yes, typically a grid tie inveter acts as a current source to \"try\"
and shove current into the grid shaped like the grid voltage waveform
itself.

I like to use the analog of two batteries with the same voltage,
paralleled together. No current flows either way. Two batteries with
one at a slightly higher voltage than battery number 2 will tend to
charge battery 1. And vice-versa.

If you look at the AC grid at any instant, it is at a particular
voltage. If you connect that AC grid to a voltage that is slightly
higher than the instantaneous grid voltage, (a sinewave or close to
it), then that voltage source will sell back to the grid.

A current source will do the same thing pretty much. If the current
waveform matches a sinewave grid, then the power factor sold back is
PF = 1.0

boB
 
On 11-10-2022 13:41, Mike Monett VE3BTI wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:

On 11-10-2022 01:24, Mike Monett VE3BTI wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:

On 10-10-2022 16:23, TTman wrote:
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...


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:

https://en.wikipedia.org/wiki/Grid-tie_inverter

Your comparison with an induction motor is misleading. There is no
motor involved.


The OP wanted an explanation. The operation of a generator is similar,
that\'s why I brought it up. It\'s all about rotating vectors, does not
matter if it is a motor or an inverter

So you know a motor is never used and instead it is an inverter.

Then why did you not say so?
Click to expand...
I was under the expression it was implicit
 
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