Synchronizing inverters with generators...

[bob prohaska]

Lately I\'ve become curious about the possiblity of using an
inverter in combination with a conventional synchronous AC
generator to supply emergency power during outages.

Initially I thought it necessary to sync the inverter clock
to the mechanical generator, but a look at a Honda EU1000i
schematic surprised me: The \"parallel outlets\" appear to
merely connect the main AC outputs. There\'s no private comms
link visible. There could of course be some kind of private RF
over power communication but I\'ve seen no hint of any such thing.

Many years ago a colleague quite skilled with electronics
built a small beat frequency audio oscillator using, I think,
555 timer circuits. To his surprise, they had a strong habit
of phase locking when the beat frequency got into the audio
range. The \"carrier\" was ~100kHz IIRC. Evidently oscillators
have some tendency to sync spontaneously, but it\'s a real
surprise if that works well enough to be useful at kilowatt
power levels.

Does anybody happen know what Honda is doing? A wiring diagram:
https://cdn.powerequipment.honda.com/pe/pdf/manuals/00X31Z406010.pdf
It\'s on page 71.

Unfortunately I don\'t know of any internal schematics for the inverter
unit. If somebody does that would be most interesting.

Thanks for reading, and any thoughts!

bob prohaska

 

[Fred Bloggs]

On Monday, October 26, 2020 at 1:50:52 PM UTC-4, bob prohaska wrote:

Lately I\'ve become curious about the possiblity of using an
inverter in combination with a conventional synchronous AC
generator to supply emergency power during outages.

Initially I thought it necessary to sync the inverter clock
to the mechanical generator, but a look at a Honda EU1000i
schematic surprised me: The \"parallel outlets\" appear to
merely connect the main AC outputs. There\'s no private comms
link visible. There could of course be some kind of private RF
over power communication but I\'ve seen no hint of any such thing.

Many years ago a colleague quite skilled with electronics
built a small beat frequency audio oscillator using, I think,
555 timer circuits. To his surprise, they had a strong habit
of phase locking when the beat frequency got into the audio
range. The \"carrier\" was ~100kHz IIRC. Evidently oscillators
have some tendency to sync spontaneously, but it\'s a real
surprise if that works well enough to be useful at kilowatt
power levels.

Does anybody happen know what Honda is doing? A wiring diagram:
https://cdn.powerequipment.honda.com/pe/pdf/manuals/00X31Z406010.pdf
It\'s on page 71.

Unfortunately I don\'t know of any internal schematics for the inverter
unit. If somebody does that would be most interesting.

Thanks for reading, and any thoughts!

bob prohaska

Explained in detail here:
https://www.freepatentsonline.com/9077207.html

 

[Whoey Louie]

On Monday, October 26, 2020 at 1:50:52 PM UTC-4, bob prohaska wrote:

Lately I\'ve become curious about the possiblity of using an
inverter in combination with a conventional synchronous AC
generator to supply emergency power during outages.

Initially I thought it necessary to sync the inverter clock
to the mechanical generator, but a look at a Honda EU1000i
schematic surprised me: The \"parallel outlets\" appear to
merely connect the main AC outputs. There\'s no private comms
link visible. There could of course be some kind of private RF
over power communication but I\'ve seen no hint of any such thing.

Many years ago a colleague quite skilled with electronics
built a small beat frequency audio oscillator using, I think,
555 timer circuits. To his surprise, they had a strong habit
of phase locking when the beat frequency got into the audio
range. The \"carrier\" was ~100kHz IIRC. Evidently oscillators
have some tendency to sync spontaneously, but it\'s a real
surprise if that works well enough to be useful at kilowatt
power levels.

Does anybody happen know what Honda is doing? A wiring diagram:
https://cdn.powerequipment.honda.com/pe/pdf/manuals/00X31Z406010.pdf
It\'s on page 71.

Unfortunately I don\'t know of any internal schematics for the inverter
unit. If somebody does that would be most interesting.

Thanks for reading, and any thoughts!

bob prohaska

IDK what they do, but inverters for solar power have a problem identical
to what you\'re describing. They need to sync the inverter output to the
AC mains.

 

[Bill Martin]

On 10/26/20 1:49 PM, Whoey Louie wrote:

On Monday, October 26, 2020 at 1:50:52 PM UTC-4, bob prohaska wrote:
Lately I\'ve become curious about the possiblity of using an
inverter in combination with a conventional synchronous AC
generator to supply emergency power during outages.

Initially I thought it necessary to sync the inverter clock
to the mechanical generator, but a look at a Honda EU1000i
schematic surprised me: The \"parallel outlets\" appear to
merely connect the main AC outputs. There\'s no private comms
link visible. There could of course be some kind of private RF
over power communication but I\'ve seen no hint of any such thing.

Many years ago a colleague quite skilled with electronics
built a small beat frequency audio oscillator using, I think,
555 timer circuits. To his surprise, they had a strong habit
of phase locking when the beat frequency got into the audio
range. The \"carrier\" was ~100kHz IIRC. Evidently oscillators
have some tendency to sync spontaneously, but it\'s a real
surprise if that works well enough to be useful at kilowatt
power levels.

Does anybody happen know what Honda is doing? A wiring diagram:
https://cdn.powerequipment.honda.com/pe/pdf/manuals/00X31Z406010.pdf
It\'s on page 71.

Unfortunately I don\'t know of any internal schematics for the inverter
unit. If somebody does that would be most interesting.

Thanks for reading, and any thoughts!

bob prohaska

IDK what they do, but inverters for solar power have a problem identical
to what you\'re describing. They need to sync the inverter output to the
AC mains.

simple PLL?

 

[boB]

On Mon, 26 Oct 2020 17:50:43 -0000 (UTC), bob prohaska
<bp@www.zefox.net> wrote:

Lately I\'ve become curious about the possiblity of using an
inverter in combination with a conventional synchronous AC
generator to supply emergency power during outages.

Initially I thought it necessary to sync the inverter clock
to the mechanical generator, but a look at a Honda EU1000i
schematic surprised me: The \"parallel outlets\" appear to
merely connect the main AC outputs. There\'s no private comms
link visible. There could of course be some kind of private RF
over power communication but I\'ve seen no hint of any such thing.

Many years ago a colleague quite skilled with electronics
built a small beat frequency audio oscillator using, I think,
555 timer circuits. To his surprise, they had a strong habit
of phase locking when the beat frequency got into the audio
range. The \"carrier\" was ~100kHz IIRC. Evidently oscillators
have some tendency to sync spontaneously, but it\'s a real
surprise if that works well enough to be useful at kilowatt
power levels.

Does anybody happen know what Honda is doing? A wiring diagram:
https://cdn.powerequipment.honda.com/pe/pdf/manuals/00X31Z406010.pdf
It\'s on page 71.

Unfortunately I don\'t know of any internal schematics for the inverter
unit. If somebody does that would be most interesting.

Thanks for reading, and any thoughts!

bob prohaska

It\'s called \"AC couplting\" in the off-grid world or on-grid PV with
backup using batteries scenario. A decent grid-tie only PV inverter
could work with that Honda inverter generator because it\'s frequency
is steady. That is, if the generator is large enough that the PV
inverter\'s anti-islanding doesn\'t trip because that inverter-generator
is fairly small compared to the grid impedance I think.

Some battery powered inverters for off-grid or backup have a feature
called \"Gen-Support\" where they synchronize with the incoming 60 Hz
generator to supply more output power than the generator can supply
by itself. The trick is to follow the wandering frequency of the
generator but of course an inverter generator like that Honda is
already very stable. Those inverter generators could do the same
thing if they had the smarts.

No communications necessary although that can make things easier. Then
it\'s called stacking inverters for more power.

You want to use an inverter with batteries to sync with it ?
Try Schneider or Outback Power or maybe Victron Energy ?

Fun stuff ! PLLs are involved but usually in software.

 

[legg]

On Mon, 26 Oct 2020 17:50:43 -0000 (UTC), bob prohaska
<bp@www.zefox.net> wrote:

Lately I\'ve become curious about the possiblity of using an
inverter in combination with a conventional synchronous AC
generator to supply emergency power during outages.

Initially I thought it necessary to sync the inverter clock
to the mechanical generator, but a look at a Honda EU1000i
schematic surprised me: The \"parallel outlets\" appear to
merely connect the main AC outputs. There\'s no private comms
link visible. There could of course be some kind of private RF
over power communication but I\'ve seen no hint of any such thing.

Many years ago a colleague quite skilled with electronics
built a small beat frequency audio oscillator using, I think,
555 timer circuits. To his surprise, they had a strong habit
of phase locking when the beat frequency got into the audio
range. The \"carrier\" was ~100kHz IIRC. Evidently oscillators
have some tendency to sync spontaneously, but it\'s a real
surprise if that works well enough to be useful at kilowatt
power levels.

Does anybody happen know what Honda is doing? A wiring diagram:
https://cdn.powerequipment.honda.com/pe/pdf/manuals/00X31Z406010.pdf
It\'s on page 71.

Unfortunately I don\'t know of any internal schematics for the inverter
unit. If somebody does that would be most interesting.

Thanks for reading, and any thoughts!

bob prohaska

Apert from the usual question \'Who\'s on first?\'; if there is a
measurable difference between two voltages (amplitude and phase),
it can be used to govern the connection.

The tie point switch or governor is not likely to be visible at
the terminal block or physical tie.

The inverter \'clock\' is not directly responsible for the output,
and may have no relationship to the power line frequency.

Low power oscillators, disconnected and decoupled, are highly
unlikely to synchronize, no matter what you thought you were
looking at. There are infinite methods of coupling that are
not obvious at first glance.

RL

 

[bob prohaska]

Fred Bloggs <bloggs.fredbloggs.fred@gmail.com> wrote:

Explained in detail here:
https://www.freepatentsonline.com/9077207.html

Aye, there\'s the rub, a little too much detail
My fluency in Patentese isn\'t quite up to the task.
Still, there are references to \"master\" and \"slave\",
implying some sort of active communication between
the inverters. What I can\'t understand is how it can
be done without any extra connections beyond the power
output lines.

Thanks for writing!

bob prohaska

 

[bob prohaska]

Whoey Louie <trader4@optonline.net> wrote:

IDK what they do, but inverters for solar power have a problem identical
to what you\'re describing. They need to sync the inverter output to the
AC mains.

That\'s a good point which I overlooked entirely.

Thank you!

bob prohaska

 

[boB]

On Tue, 27 Oct 2020 16:34:30 -0000 (UTC), bob prohaska
<bp@www.zefox.net> wrote:

Whoey Louie <trader4@optonline.net> wrote:

IDK what they do, but inverters for solar power have a problem identical
to what you\'re describing. They need to sync the inverter output to the
AC mains.


That\'s a good point which I overlooked entirely.

Thank you!

bob prohaska

Grid tie only PV inverters are comparitively easy to synchronize with
the grid since they just put out a current that is proportional to the
grid voltage.... Much like a PFC circuit draws an AC grid sinewave
shape of current from the grid. Just the other way.

A voltage source inverter like the Honda is harder but is done all the
time.

 

[Fred Bloggs]

On Tuesday, October 27, 2020 at 12:31:32 PM UTC-4, bob prohaska wrote:

Fred Bloggs <bloggs.fred...@gmail.com> wrote:

Explained in detail here:
https://www.freepatentsonline.com/9077207.html
Aye, there\'s the rub, a little too much detail
My fluency in Patentese isn\'t quite up to the task.
Still, there are references to \"master\" and \"slave\",
implying some sort of active communication between
the inverters. What I can\'t understand is how it can
be done without any extra connections beyond the power
output lines.

I don\'t think so. The diagram on page 71 of the manual shows the parallel output jack as simply a tap off the power receptacles. The inverter is pretty much a state-of-the-art switcher topology, using high power IGBTs, and probably switching at something like 30-50 kHz. The rotational speed of actual magnetics/ windings generator portion is kept high, has nothing to do with output signal frequency, doesn\'t vary all that much with loading, and is rectified to DC internally to power the inverter. It\'s the electronics in the inverter that determines output frequency, phase, amplitude, and, foremost, spectral purity of the signal , which Honda brags about quite a bit. My ***guess*** is the inverter is sampling and monitoring the possibly bidirectional power flow at the output receptacle and adjusting the signal parameters to maximize the delivered output. This would mean the two parallel generators end up splitting the load 50-50 exactly. You\'ll notice the generators
want that parallel cable installed while they\'re off, plugging it in to a hot generator might damage something. And the people mixing and matching different generator brands or models within the same brand, have no idea what they\'re doing. The Honda\'s are pricey but they pay for themselves in operating cost reduction and longevity. They\'re a good buy.

Thanks for writing!

bob prohaska

 

[Fred Bloggs]

On Tuesday, October 27, 2020 at 12:31:32 PM UTC-4, bob prohaska wrote:

Fred Bloggs <bloggs.fred...@gmail.com> wrote:

Explained in detail here:
https://www.freepatentsonline.com/9077207.html
Aye, there\'s the rub, a little too much detail
My fluency in Patentese isn\'t quite up to the task.
Still, there are references to \"master\" and \"slave\",
implying some sort of active communication between
the inverters. What I can\'t understand is how it can
be done without any extra connections beyond the power
output lines.

Thanks for writing!

bob prohaska

I should add that the parallel cable is mainly there to put the combined power on a single AC output receptacle.

 

[bob prohaska]

legg <legg@nospam.magma.ca> wrote:

Low power oscillators, disconnected and decoupled, are highly
unlikely to synchronize, no matter what you thought you were
looking at. There are infinite methods of coupling that are
not obvious at first glance.

The two 555 oscillators were on one breadboard, with the usual
power decoupling applied. Perhaps it simply wasn\'t sufficient.....

Putting the question differently: Is there a way to smoothly transition
loads from a conventional synchronous generator to a lower power
and more efficient inverter unit? The idea would be to start wtih
the synchronous generator, once the starting surge has damped out
allow the inverter unit to pick up the load and shut the synchronous
machine off. The motive is fuel efficiency. The starting load is
too much for the inverter, but the running load well within capacity.

I already have the synchronous generator and wondered, based on the
lack of explicit sync wiring, if an inverter unit capable of parallel
operation might be able to synchronize itself. I picked the Honda
EU1000i as an example simply because it\'s well-known and the manual
is on-line. I wouldn\'t expect Honda to admit their generators can be
paraleled with anybody else\'s even if the idea is workable.

An island grid tie inverter probably would do what I want, but that\'s
overkill. I\'m looking for a cheap solution to a small scale problem.

Thanks for everyone\'s insights!

bob prohaska

 

[Jasen Betts]

On 2020-10-26, bob prohaska <bp@www.zefox.net> wrote:

Lately I\'ve become curious about the possiblity of using an
inverter in combination with a conventional synchronous AC
generator to supply emergency power during outages.

Initially I thought it necessary to sync the inverter clock
to the mechanical generator, but a look at a Honda EU1000i
schematic surprised me: The \"parallel outlets\" appear to
merely connect the main AC outputs. There\'s no private comms
link visible. There could of course be some kind of private RF
over power communication but I\'ve seen no hint of any such thing.

Many years ago a colleague quite skilled with electronics
built a small beat frequency audio oscillator using, I think,
555 timer circuits. To his surprise, they had a strong habit
of phase locking when the beat frequency got into the audio
range. The \"carrier\" was ~100kHz IIRC. Evidently oscillators
have some tendency to sync spontaneously, but it\'s a real
surprise if that works well enough to be useful at kilowatt
power levels.

Does anybody happen know what Honda is doing? A wiring diagram:
https://cdn.powerequipment.honda.com/pe/pdf/manuals/00X31Z406010.pdf
It\'s on page 71.

Unfortunately I don\'t know of any internal schematics for the inverter
unit. If somebody does that would be most interesting.

Thanks for reading, and any thoughts!

Consider the simplest inverter, the Royer oscillator, (which is a kind
of blocking oscillator) connect two of them in parallel and they\'ll
self-synchronise.

I don\'t know what they actually use inside the generator

--
Jasen.

 

[Jasen Betts]

On 2020-10-28, bob prohaska <bp@www.zefox.net> wrote:

legg <legg@nospam.magma.ca> wrote:

Low power oscillators, disconnected and decoupled, are highly
unlikely to synchronize, no matter what you thought you were
looking at. There are infinite methods of coupling that are
not obvious at first glance.


The two 555 oscillators were on one breadboard, with the usual
power decoupling applied. Perhaps it simply wasn\'t sufficient.....

Putting the question differently: Is there a way to smoothly transition
loads from a conventional synchronous generator to a lower power
and more efficient inverter unit? The idea would be to start wtih
the synchronous generator, once the starting surge has damped out
allow the inverter unit to pick up the load and shut the synchronous
machine off. The motive is fuel efficiency. The starting load is
too much for the inverter, but the running load well within capacity.

I already have the synchronous generator and wondered, based on the
lack of explicit sync wiring, if an inverter unit capable of parallel
operation might be able to synchronize itself. I picked the Honda
EU1000i as an example simply because it\'s well-known and the manual
is on-line. I wouldn\'t expect Honda to admit their generators can be
paraleled with anybody else\'s even if the idea is workable.

It sounds plausable. but it\'s not stated how the generators synchronise
with each other, if the second one come up in some sort of \"slave mode\"
when you\'re using the link cables it might not work well when the
master disappears.

The manual says not to disconnect the link cables when the generator
is running, but doesn\'t say why.

--
Jasen.