Re: Can you parallel three EU2000i generators?

[Mike Swift]

One great feature of the Honda EU2000i is that the outputs of two
generators can be paralled to double the output power. The second
generator's inverter automatically synchronizes to the first generator,
and everything works.

I've always wondered whether three (or more) EU2000i generators could
be paralleled for even more power. On the surface, it seems like it
ought to work. Since the inverter is able to synchronize to a 60 Hz
waveform that is present at startup, why would it matter whether that
waveform was generated by two inverters rather than one? On the other
hand, could the third generator introduce instablity into a control
system tuned for two gnerators only?

Any thoughts?

I'm not suggesting that anybody try this, just trying to stimulate some
on-topic discussion.

From my experience in the U.S. Navy paralleling generators with
mechanical governors is very common. The only requirement is that all
generators on a bus must have the same droop setting. Droop is the
amount the generator frequency will drop as load increases. Each
generator will then put out the same percentage of its capacity as load
increases or decreases. Voltage control for each generator is used to
control the reactive power. You do not want high circulating currents
between generators that just wastes energy in the wiring.
As the Honda EUx000i models create the AC from the rectified output from
an alternator that runs frequency wild it's micro-controller does all of
the work of controlling power generation. From Honda's owners manual it
appears that the 'paralleling' kit is a junction box that takes the
outputs from two units and ties them together. Control to keep the two
inverters in sync is through the 'extra' cable in the paralleling kit.
If there are two control cable connectors on each generator they
probably have the capability of daisy chaining the control cables, and
the software to handle n paralleled generators. If there is only one
control cable connector on each generator the software would probably
not know what to do if it found it was talking to two or more other
generators.

 

[Vaughn Simon]

Control to keep the two
inverters in sync is through the 'extra' cable in the paralleling kit.

A totally logical assumption, and one that I used to share...but apparently
incorrect. The two units are simply paralled together, there is no "extra"
control wire. That is why many build their own paralleling kits.

Vaughn

 

[[email protected]]

... From Honda's owners manual it appears that the 'paralleling' kit is
a junction box that takes the outputs from two units and ties them together.

That's my impression as well.

Control to keep the two inverters in sync is through the 'extra' cable
in the paralleling kit.

Oh? Are you sure there's an "extra" cable? IIRC, the homebrew kit
on Maurice Higgins' web site didn't have any extra cable, just
a means for wiring the AC outputs together.

Nick

 

[William P.N. Smith]

Control to keep the two
inverters in sync is through the 'extra' cable in the paralleling kit.

Turns out that this completely logical reasoning is not true. The
cable in the parallel kit just connects the outputs of the two
generators together, so there's some unknown magic that syncs the two
generators. This leads to the obvious speculations:

1) Can you connect more than two generators together? This would be
especially interesting for the 2KW version, as it's got the best
$/watt metric.

2) Can you feed power back into the grid by cranking up the output
voltage (with a Variac?)

3) Can you read the load current from your total generator array and
start/stop generators (probably have to use the 3KW version, as it's
got electric start) to match the load and get the highest fuel
efficiency?

4) Could you couple the wild AC outputs of a number of generators
together (thru the appropriate fullwave blocking diodes) to feed a
battery bank that would then feed the required number of inverters, so
you could balance input and output power on a slower basis than 3)
above.

 

[Mike Swift]

A totally logical assumption, and one that I used to share...but
apparently
incorrect. The two units are simply paralled together, there is no "extra"
control wire. That is why many build their own paralleling kits.

Vaughn

It appears that you, and several others are right. The wiring schematic
for the EU2000i shows that the two paralleling lines are just single
conductor wires off of the two 120 volt inverter outputs. Their 'kit'
only bypasses the 20 amp circuit breaker used by the U ground
receptacles. With this information I would think that the only
limitation on the number of paralleled generators would be the current
handling capacity of the wiring.

 

[William P.N. Smith]

With this information I would think that the only
limitation on the number of paralleled generators would be the current
handling capacity of the wiring.

But again, there could be control system instabilities with more than
two generators that wouldn't come up with just two. Open-loop control
systems like this can't just be arbitrarily fiddled with. We'd need a
good look at their schematics and design details of their inverters to
know for sure, and IIRC they are potted modules.

An easy question to answer if anyone has $6K they don't need... 8*)

 

[Mike Swift]

But again, there could be control system instabilities with more than
two generators that wouldn't come up with just two. Open-loop control
systems like this can't just be arbitrarily fiddled with. We'd need a
good look at their schematics and design details of their inverters to
know for sure, and IIRC they are potted modules.

An easy question to answer if anyone has $6K they don't need... 8*)

I suspect that most of the control system is in software, so we would
need the source code to. I don't think Hondas going to make that
available to any of us end users .

 

[winflex]

The answer to the big question in this thread.

Leave it to the Burners. They've already tried it, and it works!

http://eplaya.burningman.com/viewtopic.php?p=258776&highlight=&sid=e963b9f0a5f57c826fa32531816f671c