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3phase PFC

J

Jamie Morken

Jan 1, 1970
0
Terry said:
Jamie said:
Terry said:
Jamie Morken wrote:

legg wrote:

Here is the ltspice circuit so far:

"http://www.rocketresearch.org/new/3phase PFC/3phaseltspice
test.zip"

Are there any 3phase PFC controller IC's out there?



- All the controller outputs were labeled for ph1 - effectively
shorted together

- All modulator references had the same phase angle. (After
correction, your model will not work with alt solver, so you'll have
to switch back to the normal solver.)

- There was no current feedback. This chip expects to see
negative-going current sensing signals on the Mout pin of less than
1V1 peak.

- Once running, you have to load it to get current waveforms.

- Don't expect to see attempted regulation prior to the 6.5mSec
timestamp, as the inrush and overshoot doesn't clear prior to that
time, even with a 1KW load. Also don't expect 60Hz performance at
600Hz.

The asc file is reworked (and still needs much more attention to run
properly as a simulation) at:

http://www.magma.ca/~legg/TVS/1249-3phase-2.zip

With simulations that take as long to run as this one does,
doublechecking your work, your ideas and your aims becomes important,
prior to pressing the GUI's 'run' button. Make sure you've got plenty
of drive space. The raw files mount up at the rate of about 150Meg per
millisecond of active converter runtime.I'm always surprised that they
run at all.

The Vienna rectifier is about the most expensive,complicated and lossy
version of PFC correction that a body could have picked.



LOL. too true. Im sure they could have added a few more diodes if
they had tried just a little bit harder


Thank you for modifying the sim to work! :)

What circuits would be better than the vienna rectifier for 3phase
PFC? I found two other ones:

http://www.rocketresearch.org/new/3phase PFC/3 phase PFC stage.png

http://www.rocketresearch.org/new/3phase PFC/3 phase PFC stage2.jpg


I would like to generate +220V and -220V rails, and use them to
generate
splitphase 120VAC sine waves using halfbridges and two LC filters.
What
would be the best 3phase PFC circuit to generate these two rails, or if
not using 3phase PFC, could a boost circuit off the 3phase 6diode
rectifier generate a positive and negative rail?

cheers,
Jamie


It sure can. use a pair of boost converters, with a half-bridge as
the switches, the center-tap of which becomes 0V. So its:


---nnnnnn---+--->|-----+--- V+
| |
3ph X [Cbig]
BR | |
+--0V------+
| |
X [Cbig]
| |
---nnnnnn---+---|<-----+--- V-


X is typically an IGBT half-bridge, but can be FETs etc.

Hi Terry,

I think this is called the "Minnesota rectifier" right? Can it
be used without the centertap neutral of the 3phase source? I think
there is no current loop unless the 3phase neutral is available, but
for my generator we don't have the neutral..

cheers,
Jamie
 
L

legg

Jan 1, 1970
0
Terry said:
Jamie said:
Terry Given wrote:

Jamie Morken wrote:
legg wrote:

The Vienna rectifier is about the most expensive,complicated and lossy
version of PFC correction that a body could have picked.



LOL. too true. Im sure they could have added a few more diodes if
they had tried just a little bit harder


Thank you for modifying the sim to work! :)

What circuits would be better than the vienna rectifier for 3phase
PFC? I found two other ones:

http://www.rocketresearch.org/new/3phase PFC/3 phase PFC stage.png

http://www.rocketresearch.org/new/3phase PFC/3 phase PFC stage2.jpg


I would like to generate +220V and -220V rails, and use them to
generate
splitphase 120VAC sine waves using halfbridges and two LC filters.
What
would be the best 3phase PFC circuit to generate these two rails, or if
not using 3phase PFC, could a boost circuit off the 3phase 6diode
rectifier generate a positive and negative rail?

cheers,
Jamie


It sure can. use a pair of boost converters, with a half-bridge as
the switches, the center-tap of which becomes 0V. So its:


---nnnnnn---+--->|-----+--- V+
| |
3ph X [Cbig]
BR | |
+--0V------+
| |
X [Cbig]
| |
---nnnnnn---+---|<-----+--- V-


X is typically an IGBT half-bridge, but can be FETs etc.

Hi Terry,

I think this is called the "Minnesota rectifier" right? Can it
be used without the centertap neutral of the 3phase source? I think
there is no current loop unless the 3phase neutral is available, but
for my generator we don't have the neutral..

cheers,
Jamie
I drew it, above. I didnt include the current sensing, or the controller
of course.

vienna rectifiers suck so bad its funny. Rob Legg outlined the reasons why.

I've never designed one of these, but I have used a 300kW version. done
with a single IGBT half-bridge, and some honking great inductors.

The existence of the generator's neutral terminal is something that
might be profitable to investigate further. Perhaps you could consult
the manual, or take a closer look at the actual hardware wiring. It's
your generator; you can do what you want with it.

You might want to think simple:

http://scholar.lib.vt.edu/theses/available/etd-2113131549741341/

The single-switch 3ph pfc circuit is probably best applied off-line,
where filtering requirement of the critical conduction current is set
by known hardware, and not paper standards.

With a generator as a source, there is no actual inrush problem, as
you are never going to be hot plugging the converter into a running
generator.

RL
 
L

legg

Jan 1, 1970
0
Great paper!
Thanks,

.....but by no means error-free.

With Mr M., it seems better to supply single in-depth refs about
single issues, rather than a host of references that just get him
wandering again.

A single switch requiring no complex or super-high-frequency
modulation is something that can be modeled fairly accurately.

You can also throw big uncomplicated components at it, though split
three ways, none of the other parts, besides the switch and PFC
rectifier need to swot the whole load.

RL
 
L

legg

Jan 1, 1970
0
You might want to think simple:

http://scholar.lib.vt.edu/theses/available/etd-2113131549741341/

The single-switch 3ph pfc circuit is probably best applied off-line,
where filtering requirement of the critical conduction current is set
by known hardware, and not paper standards.

With a generator as a source, there is no actual inrush problem, as
you are never going to be hot plugging the converter into a running
generator.

Just a little warning about this and other single-switch 3ph pfc
topologies.

It may not be obvious, but when the pfc chokes are in the line like
this, the entire downstream cicuitry has boost switch noise imposed
upon it, including bulk caps and downstream converters. This places
obvious cmrr problems (with respect to the rest of the universe) on
any control circuitry directly connected to it, and introduces serious
emc compliance issues.

Luckily, any information that needs processing or communication is
relatively simple. Functional troubleshooting can be tricky - don't
expect to be able to just stick you grounded scope probe anywhere you
please.

RL
 
J

Jamie Morken

Jan 1, 1970
0
legg said:
Just a little warning about this and other single-switch 3ph pfc
topologies.

It may not be obvious, but when the pfc chokes are in the line like
this, the entire downstream cicuitry has boost switch noise imposed
upon it, including bulk caps and downstream converters. This places
obvious cmrr problems (with respect to the rest of the universe) on
any control circuitry directly connected to it, and introduces serious
emc compliance issues.

Luckily, any information that needs processing or communication is
relatively simple. Functional troubleshooting can be tricky - don't
expect to be able to just stick you grounded scope probe anywhere you
please.

Hi,

A bit off topic, but I also have a split phase inverter that has a
similar technique of injection, but its with the 120VAC common:

"http://www.rocketresearch.org/new/split phase 240VAC inverter/splitphaseinverter.jpg"

The red bar is a +440VDC rail, and then there are two half bridges to
give 120VAC/60Hz 180degrees out of phase, and they are centered around
~220VDC, which is the 120VAC common, held by the middle half bridge.

Will this setup work ok, and does it have the same CMRR problems
due to the series L in the common return? The L is quite small,
probably 20uH or less for the common.

cheers,
Jamie
 
L

legg

Jan 1, 1970
0
Hi,

A bit off topic, but I also have a split phase inverter that has a
similar technique of injection, but its with the 120VAC common:

"http://www.rocketresearch.org/new/split phase 240VAC inverter/splitphaseinverter.jpg"
...and only nine components. Amazing!
The red bar is a +440VDC rail, and then there are two half bridges to
give 120VAC/60Hz 180degrees out of phase, and they are centered around
~220VDC, which is the 120VAC common, held by the middle half bridge.

Will this setup work ok, and does it have the same CMRR problems
due to the series L in the common return? The L is quite small,
probably 20uH or less for the common.

There's no high frequency interference if the 440VDC is clean. The
inverter outputs should only inter-tie through a working load.

You seem not only to be jumping between topologies, but are now going
backwards, ie generating three-phase from some unknown source.

Problems are a lot easier to deal with if there is a fixed goal.

RL
 
L

legg

Jan 1, 1970
0
Hi,

A bit off topic, but I also have a split phase inverter that has a
similar technique of injection, but its with the 120VAC common:

"http://www.rocketresearch.org/new/split phase 240VAC inverter/splitphaseinverter.jpg"

The red bar is a +440VDC rail, and then there are two half bridges to
give 120VAC/60Hz 180degrees out of phase, and they are centered around
~220VDC, which is the 120VAC common, held by the middle half bridge.

Will this setup work ok, and does it have the same CMRR problems
due to the series L in the common return? The L is quite small,
probably 20uH or less for the common.

Wait a minute.

Are you saying that you intend to connect one of your inverter outputs
to hydro neutral (ie ground) ?

Might I ask, why?

Unless there is some galvanic isolation somewhere back in the power
train, this will look like a short to somewhere.

If there IS isolation, you'll be driving the entire system with the
inverter 'output' voltage, where driving interphase loads normally
will only induce hf and modulation balancing errors on the system
hardware.

RL
 
J

JosephKK

Jan 1, 1970
0
Terry said:
Jamie Morken wrote:
Terry Given wrote:

Jamie Morken wrote:
legg wrote:

The Vienna rectifier is about the most expensive,complicated and lossy
version of PFC correction that a body could have picked.



LOL. too true. Im sure they could have added a few more diodes if
they had tried just a little bit harder


Thank you for modifying the sim to work! :)

What circuits would be better than the vienna rectifier for 3phase
PFC? I found two other ones:

http://www.rocketresearch.org/new/3phase PFC/3 phase PFC stage.png

http://www.rocketresearch.org/new/3phase PFC/3 phase PFC stage2.jpg


I would like to generate +220V and -220V rails, and use them to
generate
splitphase 120VAC sine waves using halfbridges and two LC filters.
What
would be the best 3phase PFC circuit to generate these two rails, or if
not using 3phase PFC, could a boost circuit off the 3phase 6diode
rectifier generate a positive and negative rail?

cheers,
Jamie


It sure can. use a pair of boost converters, with a half-bridge as
the switches, the center-tap of which becomes 0V. So its:


---nnnnnn---+--->|-----+--- V+
| |
3ph X [Cbig]
BR | |
+--0V------+
| |
X [Cbig]
| |
---nnnnnn---+---|<-----+--- V-


X is typically an IGBT half-bridge, but can be FETs etc.

Hi Terry,

I think this is called the "Minnesota rectifier" right? Can it
be used without the centertap neutral of the 3phase source? I think
there is no current loop unless the 3phase neutral is available, but
for my generator we don't have the neutral..

cheers,
Jamie
Hi Terry,

Thanks for the dual rail boost! ;)


the same trick used to make a single-phase boost PFC (force current
to follow envelope of full-wave rectified line voltage) also works
for three-phase systems; the 6-diode bridge automagically "unfolds"
the current waveform.


Is this an alternate circuit to the vienna rectifier for 3phase PFC?
Do you have a schematic of it?

I drew it, above. I didnt include the current sensing, or the controller
of course.

vienna rectifiers suck so bad its funny. Rob Legg outlined the reasons why.

I've never designed one of these, but I have used a 300kW version. done
with a single IGBT half-bridge, and some honking great inductors.



Here's an ltspice sim from Larry Carroll on the ltspice yahoo
group, it implements 3phase PFC with one cycle PFC control!

"http://www.rocketresearch.org/new/3phase PFC/lbcarroll backup.zip"

The existence of the generator's neutral terminal is something that
might be profitable to investigate further. Perhaps you could consult
the manual, or take a closer look at the actual hardware wiring. It's
your generator; you can do what you want with it.

Actually, it is more likely than not that it is wound delta rather
than wye. There are reasons for doing this.
You might want to think simple:

http://scholar.lib.vt.edu/theses/available/etd-2113131549741341/

The single-switch 3ph pfc circuit is probably best applied off-line,
where filtering requirement of the critical conduction current is set
by known hardware, and not paper standards.

With a generator as a source, there is no actual inrush problem, as
you are never going to be hot plugging the converter into a running
generator.

Not true. Many Motor-Generator sets feed into automatic bus transfer
switches.
 
L

legg

Jan 1, 1970
0
Not true. Many Motor-Generator sets feed into automatic bus transfer
switches.

If that were the case, then inrush would have to be addressed.

So far, that spanner hasn't been thown into the works, but I'm sure
the OP will eventually get round to it.

RL
 
J

Jamie Morken

Jan 1, 1970
0
legg said:
Wait a minute.

Are you saying that you intend to connect one of your inverter outputs
to hydro neutral (ie ground) ?

Might I ask, why?

Yes, the halfbridge output that is connected to hydro neutral (ground)
is there as the current return for the two 120VAC outputs, it just holds
a constant DC voltage, which the two 120VAC phases are centered around,
since 120VAC loads run from phase to neutral.

cheers,
Jamie
 
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