Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Mark Frye]

Thanks Brad,

I think I am finally getting it.

When on-grid, the grid is providing wave form and transistors in BB are 
available to provide voltage regulation.


When off-grid, the transistors in the BB are required to provided wave 
form and not available to provide regulation.



On 11/4/2019 6:10 AM, Bradley Bassett wrote:

Mark,

The difference is that when AC coupled the power is coming backwards 
into the AC out. When it's charging from the grid or generator it is 
charging from the AC inputs. The inverter can control the charge from 
the inputs but not what is coming in reverse into the output.


Brad

On Sun, Nov 3, 2019 at 6:10 PM Mark Frye > wrote:


OK Jay that makes sense.

This must mean that there is a significant difference in the
function of
the BB inverter when it is in off-grid mode vs when it is in grid
connected mode.

On 11/3/2019 5:45 PM, jay wrote:
> No, older non frequency shift BB inverters don’t communicate
that way.
>
> They have no communication with a Rule 21 GT inverter.
>
> The BB, it will just keep charging and charging with any extra
energy coming from the GT inverter.  The BB  has no regulation,
there is no absorb or float, just charge.
>
> jay
>
> peltz power
>
>> On Nov 3, 2019, at 4:31 PM, Mark Frye mailto:ma...@berkeleysolar.com>> wrote:
>>
>> OK, I am hearing this over and over and I just want to confirm
that is true even if the BB is older and does not have "NEW
Frequency Shifting AC Coupling".
>>
>> On 11/3/2019 4:26 PM, Dave Angelini Offgrid Solar wrote:
>>> The BB inverter will drive the grid inverter off frequency
because it is
>>> full/floating and the grid tie will stop producing power. This
is how AC
>>> coupling works but if something goes wrong, like programming
gets corrupted
>>> by surges or the battery hits an LBCO or HBCO AC power will
stop. Or if
>>> this is being controlled by Soc and it gets wrong data or
there is a
>>> network issue, or all of the other things that can happen that
I have not
>>> thought of.
>>>
>>> Why do you not want to build a normal DC couples system? I forget
>>> fastHappy Hour!
>>>
>>> Dave Angelini Offgrid Solar
>>> "we go where powerlines don't"
>>> http://members.sti.net/offgridsolar/
>>> e-mail offgridso...@sti.net 
>>> text 209 813 0060
>>>
>>> On Sun, 3 Nov 2019 16:17:39 -0800, Mark Frye
mailto:ma...@berkeleysolar.com>>
>>> wrote:
 Folks,

 Please allow me to ask another question:

 Suppose I have a bi-direction inverter/charge with no
connection to the
 grid.

 I have GT inverter ac coupled and producing 2000w. The
battery is in
 float, and I have 2000w of load connected. All is well.

 Now suppose I remove the loads without disconnecting the GT
inverters.

 The word is that something bad happens now. I would like to
understand
 what that bad thing is.

 I have one explanation that I think says that the GTs will
continue to
 produce the 2000w, and that energy will go into the batteries
in an
 unregulated fashion. When does this end, when the batteries
blow up? Is
 that the consequence of not disconnecting the GT?

 With many thanks in advance for your help in understanding.

 Mark

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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Bradley Bassett]

Mark,

The difference is that when AC coupled the power is coming backwards into
the AC out. When it's charging from the grid or generator it is charging
from the AC inputs. The inverter can control the charge from the inputs but
not what is coming in reverse into the output.

Brad

On Sun, Nov 3, 2019 at 6:10 PM Mark Frye  wrote:

> OK Jay that makes sense.
>
> This must mean that there is a significant difference in the function of
> the BB inverter when it is in off-grid mode vs when it is in grid
> connected mode.
>
> On 11/3/2019 5:45 PM, jay wrote:
> > No, older non frequency shift BB inverters don’t communicate that way.
> >
> > They have no communication with a Rule 21 GT inverter.
> >
> > The BB, it will just keep charging and charging with any extra energy
> coming from the GT inverter.  The BB  has no regulation, there is no absorb
> or float, just charge.
> >
> > jay
> >
> > peltz power
> >
> >> On Nov 3, 2019, at 4:31 PM, Mark Frye  wrote:
> >>
> >> OK, I am hearing this over and over and I just want to confirm that is
> true even if the BB is older and does not have "NEW Frequency Shifting AC
> Coupling".
> >>
> >> On 11/3/2019 4:26 PM, Dave Angelini Offgrid Solar wrote:
> >>> The BB inverter will drive the grid inverter off frequency because it
> is
> >>> full/floating and the grid tie will stop producing power. This is how
> AC
> >>> coupling works but if something goes wrong, like programming gets
> corrupted
> >>> by surges or the battery hits an LBCO or HBCO AC power will stop. Or if
> >>> this is being controlled by Soc and it gets wrong data or there is a
> >>> network issue, or all of the other things that can happen that I have
> not
> >>> thought of.
> >>>
> >>> Why do you not want to build a normal DC couples system? I forget
> >>> fastHappy Hour!
> >>>
> >>> Dave Angelini Offgrid Solar
> >>> "we go where powerlines don't"
> >>> http://members.sti.net/offgridsolar/
> >>> e-mail offgridso...@sti.net
> >>> text 209 813 0060
> >>>
> >>> On Sun, 3 Nov 2019 16:17:39 -0800, Mark Frye 
> >>> wrote:
>  Folks,
> 
>  Please allow me to ask another question:
> 
>  Suppose I have a bi-direction inverter/charge with no connection to
> the
>  grid.
> 
>  I have GT inverter ac coupled and producing 2000w. The battery is in
>  float, and I have 2000w of load connected. All is well.
> 
>  Now suppose I remove the loads without disconnecting the GT inverters.
> 
>  The word is that something bad happens now. I would like to understand
>  what that bad thing is.
> 
>  I have one explanation that I think says that the GTs will continue to
>  produce the 2000w, and that energy will go into the batteries in an
>  unregulated fashion. When does this end, when the batteries blow up?
> Is
>  that the consequence of not disconnecting the GT?
> 
>  With many thanks in advance for your help in understanding.
> 
>  Mark
> 
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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Mark Frye]

OK Jay that makes sense.

This must mean that there is a significant difference in the function of 
the BB inverter when it is in off-grid mode vs when it is in grid 
connected mode.


On 11/3/2019 5:45 PM, jay wrote:

No, older non frequency shift BB inverters don’t communicate that way.

They have no communication with a Rule 21 GT inverter.

The BB, it will just keep charging and charging with any extra energy coming 
from the GT inverter.  The BB  has no regulation, there is no absorb or float, 
just charge.

jay

peltz power


On Nov 3, 2019, at 4:31 PM, Mark Frye  wrote:

OK, I am hearing this over and over and I just want to confirm that is true even if the 
BB is older and does not have "NEW Frequency Shifting AC Coupling".

On 11/3/2019 4:26 PM, Dave Angelini Offgrid Solar wrote:

The BB inverter will drive the grid inverter off frequency because it is
full/floating and the grid tie will stop producing power. This is how AC
coupling works but if something goes wrong, like programming gets corrupted
by surges or the battery hits an LBCO or HBCO AC power will stop. Or if
this is being controlled by Soc and it gets wrong data or there is a
network issue, or all of the other things that can happen that I have not
thought of.

Why do you not want to build a normal DC couples system? I forget
fastHappy Hour!

Dave Angelini Offgrid Solar
"we go where powerlines don't"
http://members.sti.net/offgridsolar/
e-mail offgridso...@sti.net
text 209 813 0060

On Sun, 3 Nov 2019 16:17:39 -0800, Mark Frye 
wrote:

Folks,

Please allow me to ask another question:

Suppose I have a bi-direction inverter/charge with no connection to the
grid.

I have GT inverter ac coupled and producing 2000w. The battery is in
float, and I have 2000w of load connected. All is well.

Now suppose I remove the loads without disconnecting the GT inverters.

The word is that something bad happens now. I would like to understand
what that bad thing is.

I have one explanation that I think says that the GTs will continue to
produce the 2000w, and that energy will go into the batteries in an
unregulated fashion. When does this end, when the batteries blow up? Is
that the consequence of not disconnecting the GT?

With many thanks in advance for your help in understanding.

Mark

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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[jay]

No, older non frequency shift BB inverters don’t communicate that way. 

They have no communication with a Rule 21 GT inverter.

The BB, it will just keep charging and charging with any extra energy coming 
from the GT inverter.  The BB  has no regulation, there is no absorb or float, 
just charge.

jay

peltz power

> On Nov 3, 2019, at 4:31 PM, Mark Frye  wrote:
> 
> OK, I am hearing this over and over and I just want to confirm that is true 
> even if the BB is older and does not have "NEW Frequency Shifting AC 
> Coupling".
> 
> On 11/3/2019 4:26 PM, Dave Angelini Offgrid Solar wrote:
>> The BB inverter will drive the grid inverter off frequency because it is
>> full/floating and the grid tie will stop producing power. This is how AC
>> coupling works but if something goes wrong, like programming gets corrupted
>> by surges or the battery hits an LBCO or HBCO AC power will stop. Or if
>> this is being controlled by Soc and it gets wrong data or there is a
>> network issue, or all of the other things that can happen that I have not
>> thought of.
>> 
>> Why do you not want to build a normal DC couples system? I forget
>> fastHappy Hour!
>> 
>> Dave Angelini Offgrid Solar
>> "we go where powerlines don't"
>> http://members.sti.net/offgridsolar/
>> e-mail offgridso...@sti.net
>> text 209 813 0060
>> 
>> On Sun, 3 Nov 2019 16:17:39 -0800, Mark Frye 
>> wrote:
>>> Folks,
>>> 
>>> Please allow me to ask another question:
>>> 
>>> Suppose I have a bi-direction inverter/charge with no connection to the
>>> grid.
>>> 
>>> I have GT inverter ac coupled and producing 2000w. The battery is in
>>> float, and I have 2000w of load connected. All is well.
>>> 
>>> Now suppose I remove the loads without disconnecting the GT inverters.
>>> 
>>> The word is that something bad happens now. I would like to understand
>>> what that bad thing is.
>>> 
>>> I have one explanation that I think says that the GTs will continue to
>>> produce the 2000w, and that energy will go into the batteries in an
>>> unregulated fashion. When does this end, when the batteries blow up? Is
>>> that the consequence of not disconnecting the GT?
>>> 
>>> With many thanks in advance for your help in understanding.
>>> 
>>> Mark
>>> 
>>> ___
>>> List sponsored by Redwood Alliance
>>> 
>>> List Address: RE-wrenches@lists.re-wrenches.org
>>> 
>>> Change listserver email address & settings:
>>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Mark Frye]

OK, I am hearing this over and over and I just want to confirm that is 
true even if the BB is older and does not have "NEW Frequency Shifting 
AC Coupling".


On 11/3/2019 4:26 PM, Dave Angelini Offgrid Solar wrote:

The BB inverter will drive the grid inverter off frequency because it is
full/floating and the grid tie will stop producing power. This is how AC
coupling works but if something goes wrong, like programming gets corrupted
by surges or the battery hits an LBCO or HBCO AC power will stop. Or if
this is being controlled by Soc and it gets wrong data or there is a
network issue, or all of the other things that can happen that I have not
thought of.

Why do you not want to build a normal DC couples system? I forget
fastHappy Hour!

Dave Angelini Offgrid Solar
"we go where powerlines don't"
http://members.sti.net/offgridsolar/
e-mail offgridso...@sti.net
text 209 813 0060

On Sun, 3 Nov 2019 16:17:39 -0800, Mark Frye 
wrote:

Folks,

Please allow me to ask another question:

Suppose I have a bi-direction inverter/charge with no connection to the
grid.

I have GT inverter ac coupled and producing 2000w. The battery is in
float, and I have 2000w of load connected. All is well.

Now suppose I remove the loads without disconnecting the GT inverters.

The word is that something bad happens now. I would like to understand
what that bad thing is.

I have one explanation that I think says that the GTs will continue to
produce the 2000w, and that energy will go into the batteries in an
unregulated fashion. When does this end, when the batteries blow up? Is
that the consequence of not disconnecting the GT?

With many thanks in advance for your help in understanding.

Mark

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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Dave Angelini Offgrid Solar]

The BB inverter will drive the grid inverter off frequency because it is
full/floating and the grid tie will stop producing power. This is how AC
coupling works but if something goes wrong, like programming gets corrupted
by surges or the battery hits an LBCO or HBCO AC power will stop. Or if
this is being controlled by Soc and it gets wrong data or there is a
network issue, or all of the other things that can happen that I have not
thought of. 

Why do you not want to build a normal DC couples system? I forget
fastHappy Hour!

Dave Angelini Offgrid Solar
"we go where powerlines don't"
http://members.sti.net/offgridsolar/
e-mail offgridso...@sti.net
text 209 813 0060

On Sun, 3 Nov 2019 16:17:39 -0800, Mark Frye 
wrote:
> Folks,
> 
> Please allow me to ask another question:
> 
> Suppose I have a bi-direction inverter/charge with no connection to the 
> grid.
> 
> I have GT inverter ac coupled and producing 2000w. The battery is in 
> float, and I have 2000w of load connected. All is well.
> 
> Now suppose I remove the loads without disconnecting the GT inverters.
> 
> The word is that something bad happens now. I would like to understand 
> what that bad thing is.
> 
> I have one explanation that I think says that the GTs will continue to 
> produce the 2000w, and that energy will go into the batteries in an 
> unregulated fashion. When does this end, when the batteries blow up? Is 
> that the consequence of not disconnecting the GT?
> 
> With many thanks in advance for your help in understanding.
> 
> Mark
> 
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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Mark Frye]

Folks,

Please allow me to ask another question:

Suppose I have a bi-direction inverter/charge with no connection to the 
grid.


I have GT inverter ac coupled and producing 2000w. The battery is in 
float, and I have 2000w of load connected. All is well.


Now suppose I remove the loads without disconnecting the GT inverters.

The word is that something bad happens now. I would like to understand 
what that bad thing is.


I have one explanation that I think says that the GTs will continue to 
produce the 2000w, and that energy will go into the batteries in an 
unregulated fashion. When does this end, when the batteries blow up? Is 
that the consequence of not disconnecting the GT?


With many thanks in advance for your help in understanding.

Mark

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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Mark Frye]

Folks,


I do not want to be obdurate here, perhaps just a slow learner.


I have to ask the question though:


In the case of a BB inverter connected to the grid only, with no GT 
inverters, you don't have to shutdown the whole inverter when the 
battery is full because you are not required to endlessly push available 
energy into the batteries. You can turn off the switch that connects the 
charger to the battery.



Mark


On 11/3/2019 11:13 AM, Kienan Maxfield wrote:

Mark,

Sorry, my post must not have been perfectly clear... I have total 
confidence in how the BB inverters work, and no, the GT inverter there 
will be no measurable deduction in impedance, even if you have a very 
sensitive sensor and there are no other loads on the system. It just 
doesn't work that way. It is impossible for the inverter to reduce the 
current into the batteries when it's being fed into the inverter 
through its output. And that's true no matter what inverter we're 
talking about. It is impossible for it to increase it's impedance that 
way.


The only thing I would say is that if you were an engineer at an 
inverter manufacturer, it would be possible for you to design an 
inverter that could change it's output voltage based on the battery 
voltage, but nobody does that. That's why they change the output 
frequency. I think my last email layed out the 4 possible options, and 
I am confident that there is no other option that would work at all.


These were my four options...

 1. Use a BB inverter that has frequency shifting control for AC coupling
 2. Run a wire from the battery room to the GT inverters that you can
use for controlling them based on the battery voltage
 3. Experiment with something custom and just expect a high
probability of eventual failure (but let us know how it goes)
 1. You might be able to find a device that would read the battery
voltage, and then transmit that information wirelessly, then
have another device at the GT inverters that decodes that
information and then drives a relay accordingly. (I have no
idea how to do this, for me, this is in the hypothetical
realm.) Or maybe it could transmit the info via PLC?
 4. Or the fourth option is to set the BB inverter's high battery cut
out voltage to just above the absorb voltage and just plan on the
power going out multiple times per sunny day. I wouldn't go for
this one unless it's your own home and you're feeling very
adventuresome.




Sorry for the bad news, but unless you have frequency shifting, it's 
totally impossible to control the GT inverter using the AC line.


Kienan


*Maxfield Solar*
*maxfieldso...@hotmail.com* <mailto:maxfieldso...@hotmail.com>
*
**(801) 631-5584 (Cell)**
*

*From:* RE-wrenches  on 
behalf of Mark Frye 

*Sent:* Sunday, November 3, 2019 11:58 AM
*To:* re-wrenches@lists.re-wrenches.org 


*Subject:* Re: [RE-wrenches] Parts List For AC Couple Disconnect

OK, the posts are coming in on the "no" side, but with uncertainty 
about how any given BB inverter might work.



I still think that the BB charger is in charge (no pun) of sending 
power to the battery and if it the battery is at it's set point then 
the duty cycle on the transistors in the rectifier go down - zero. At 
that point the impedance of the AC line would appear to go up. In 
response the GT inverters would increase there output voltage in an 
attempt to over come the higher impedance.



The voltage monitoring switch that I spec'd has a response delay 
setting. If I am running in offgrid mode, the main worry is voltage 
sag due to load. So generally, the inverter would be running at or 
below AC voltage set point. There may be spikes above voltage set 
point when a load is disconnected, but I could filter that out with 
the delay on the sensor.



Still, this is why I am asking.


Anyone on the list have more confidence in their understand of BB 
inverters in off-grid mode with AC coupled GT inverters?



Mark


On 11/3/2019 10:44 AM, Kienan Maxfield wrote:

Mark,

I think that you're not understanding what Brian is saying. In any 
case, your proposal will not work with most equipment. There may be 
some equipment that would work that way, but not anything I'm aware 
of. Let me tell you what will happen in a normal system, assuming 
that the manufacturer hasn't built in an AC coupling control 
mechanism (like frequency shifting)


The BB inverter will maintain a stable AC voltage by allowing the GT 
inverters to back feed into the batteries. If the batteries start 
overcharging, the BB inverter will not raise the AC voltage in 
response. What will happen instead is that there will be no 
measurable difference in the AC voltage, but the DC voltage will 
continue to rise until it hits the multimode BB inverter

Re: [RE-wrenches] Parts List For AC Couple Disconnect

[jay]

An option that will work for sure is a diversion load and controller.  

This can be done with most standard CC’s and or inverters using the AUX relay 
driving another SS relay, and then the diversion load.  The load can be a 
standard AC oil heater, safe, inexpensive, reliable.  ( this is what I use for 
my own hydro diversion)
The size of the diversion would depend on battery bank size, type, GTI size, 
system load etc.  

As to cost, sub $100 in parts.

I’m thinking that Kienan is right here. AC coupling control is done on the 
frequency side, not any change in AC voltage. 

My experience with doing it in the past on my own system didn’t show any change 
in AC voltage. But it wasn’t a large AC couple production vs size of the 
inverter ( 600 watts vs 3500 inverter) so maybe I didn’t have enough 
to drive up the AC volts?

jay

peltz power

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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Ray]

I wouldn't go for
this one unless it's your own home and you're feeling very
adventuresome.

Essentially the bottom line is that monitoring the AC line will never 
work unless the BB inverter has a built-in AC coupling control 
mechanism, then you'll be monitoring for the frequency rather than 
the voltage.


Sorry for not having anything more helpful to say.
Kienan

*Maxfield Solar*
*maxfieldso...@hotmail.com* <mailto:maxfieldso...@hotmail.com>
*
**(801) 631-5584 (Cell)**
*

*From:* RE-wrenches  on 
behalf of Mark Frye 

*Sent:* Sunday, November 3, 2019 11:00 AM
*To:* re-wrenches@lists.re-wrenches.org 


*Subject:* Re: [RE-wrenches] Parts List For AC Couple Disconnect
OK Brian,

So I think you are confirming that monitoring AC side voltage is an
acceptable way of deciding when to disconnect the GT inverters.

With my parts list, I have a delay time that would hold the GT inverters
off-line for some period of time (I would probably set to 1 hour) before
coming back on line after tipping off.


Mark

On 11/3/2019 9:53 AM, Brian Mehalic wrote:
> With frequency-on/off, frequency power control, or other “inverter 
integrated” control based on battery voltage/state of charge there is 
also control in regards to when the ac coupled inverters come back 
on. And yes, this is definitely needed to prevent overcharge (or get 
three-stage charging from the  AC coupled system). Of course if it 
doesn’t work, yes the bus voltage will rise and trip the BB offline.

>
> AC bus voltage will go down as soon as the ac couple inverters are 
kicked off, so if that’s your measured value unless your control 
system has a delay or other component to control reconnection and 
charging i think it could essentially chatter off and on and off and...

>
> Brian
>
>> On Nov 3, 2019, at 9:38 AM, Mark Frye  wrote:
>>
>> Hi William,
>>
>> Thanks, you bring up issues that are important to me here.
>>
>> In particular, my situation is that the GT inverter is inter-tied 
a couple sub panels upstream of where I want to put the BB inverter. 
The distance is long, so I am looking for a solution where I don't 
have to run a cable between the two.

>>
>> In general, I do wonder about using AC line voltage rise to take 
the Gt inverters off line. The main goal is to prevent excess voltage 
at the battery, so monitoring battery voltage is most direct, and 
there are simple solutions for that.

>>
>> Is AC line voltage a suitable metric for achieving the same goal?
>>
>> Here is where I could use Wrench knowledge to confirm my thinking, 
that being:

>>
>> - With excess energy in the system, the charger moves it into the 
battery, raising it's voltage until it reaches it high charging 
voltage set point

>>
>> - Once the battery reaches it's high voltage set point, the 
charger stops putting energy into the battery

>>
>> - With no other place to put the excess energy, the AC voltage rises
>>
>> Am I getting this right, the reason to disconnect AC coupled 
inverters when the battery if full is not to prevent the batteries 
from being overcharged, but rather to prevent the AC line from 
becoming unstable?

>>
>> I am hoping this is correct and that with $200 of industrial grade 
devices from Digikey I can implement a robust control that will 
disconnect the GT inverters before the AC line goes so high that the 
BB inverter faults.

>>
>> Mark
>>
>>
>>
>> ___
>> List sponsored by Redwood Alliance
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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Glenn Burt]

to find a device that would read the
  battery voltage, and then transmit that
 information
  wirelessly, then have another device at the GT inverters
  that decodes that information and then drives a relay
  accordingly. (I have no idea how to do this, for me, this
  is in the hypothetical realm.) Or maybe it could transmit
  the info via PLC?
  
  or
the fourth option is to set the BB inverter's high
battery cut out voltage to just above the absorb voltage
and just plan on the power going out multiple times per
sunny day. I wouldn't go for this one unless it's your
own home and you're feeling very adventuresome.

Essentially the bottom
  line is that monitoring the AC line will never work unless
  the BB inverter has a built-in AC
coupling control mechanism, then you'll be monitoring for
the frequency rather than the voltage.
  
  
   
 
  
  
Sorry for not having anything more helpful to say.
  
Kienan
  

  
  Maxfield Solar
maxfieldso...@hotmail.com


  (801)
  631-5584 (Cell)

  

  
  
  From:
  RE-wrenches 
  on behalf of Mark Frye 
  Sent: Sunday, November 3, 2019 11:00 AM
  To: re-wrenches@lists.re-wrenches.org
  
  Subject: Re: [RE-wrenches] Parts List For AC Couple
  Disconnect
 
  
  
OK Brian,
  
  So I think you are confirming that monitoring AC side
  voltage is an 
  acceptable way of deciding when to disconnect the GT
  inverters.
  
   
   With my parts list, I have a delay time that would hold
  the GT inverters 
  off-line for some period of time (I would probably set to
  1 hour) before 
  coming back on line after tipping off.
  
  
  Mark
  
  On 11/3/2019 9:53 AM, Brian Mehalic wrote:
  > With frequency-on/off, frequency power control, or
  other “inverter integrated” control based on battery
  voltage/state of charge there is also control in regards
  to when the ac coupled inverters come back on. And yes,
  this is definitely needed to prevent overcharge (or get
  three-stage charging from the  AC coupled system). Of
  course if it doesn’t work, yes the bus voltage will rise
  and trip the BB offline.
  >
  > AC bus voltage will go down as soon as the ac couple
  inverters
 are kicked off, so if that’s your measured value
  unless your control system has a delay or other component
  to control reconnection and charging i think it could
  essentially chatter off and on and off and...
  >
  > Brian
  >
  >> On Nov 3, 2019, at 9:38 AM, Mark Frye
   wrote:
  >>
  >> Hi William,
  >>
  >> Thanks, you bring up issues that are important to
  me here.
  >>
  >> In particular, my situation is that the GT
  inverter is inter-tied a couple sub panels upstream of
  where I want to put the BB inverter. The distance is long,
  so I am looking for a solution where I don't have to run a
  cable between the two.
  >>
  >> In general, I do wonder about using AC line
  voltage rise to
 take the Gt inverters off line. The main
  goal is to prevent excess voltage at the battery, so
  monitoring battery voltage is most direct, and there are
  simple solutions for that.
  >>
  >> Is AC line voltage a suitable metric for
  achieving the same goal?
  >>
  >> Here is where I could use Wrench knowledge to
  confirm my thinking, that being:
  >>
  >> - With excess energy in the system, the charger
  moves it into the battery, raising it's voltage until it
  reaches it high charging voltage set point
  >>
  >> - Once the battery reaches it's high voltage set
  point, the charger stops putting energy into the battery
  >>
  >> - With no other place 

Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Kienan Maxfield]

Mark,

Sorry, my post must not have been perfectly clear... I have total confidence in 
how the BB inverters work, and no, the GT inverter there will be no measurable 
deduction in impedance, even if you have a very sensitive sensor and there are 
no other loads on the system. It just doesn't work that way. It is impossible 
for the inverter to reduce the current into the batteries when it's being fed 
into the inverter through its output. And that's true no matter what inverter 
we're talking about. It is impossible for it to increase it's impedance that 
way.

The only thing I would say is that if you were an engineer at an inverter 
manufacturer, it would be possible for you to design an inverter that could 
change it's output voltage based on the battery voltage, but nobody does that. 
That's why they change the output frequency. I think my last email layed out 
the 4 possible options, and I am confident that there is no other option that 
would work at all.

These were my four options...

  1.  Use a BB inverter that has frequency shifting control for AC coupling
  2.  Run a wire from the battery room to the GT inverters that you can use for 
controlling them based on the battery voltage
  3.  Experiment with something custom and just expect a high probability of 
eventual failure (but let us know how it goes)
 *   You might be able to find a device that would read the battery 
voltage, and then transmit that information wirelessly, then have another 
device at the GT inverters that decodes that information and then drives a 
relay accordingly. (I have no idea how to do this, for me, this is in the 
hypothetical realm.) Or maybe it could transmit the info via PLC?
  4.  Or the fourth option is to set the BB inverter's high battery cut out 
voltage to just above the absorb voltage and just plan on the power going out 
multiple times per sunny day. I wouldn't go for this one unless it's your own 
home and you're feeling very adventuresome.



Sorry for the bad news, but unless you have frequency shifting, it's totally 
impossible to control the GT inverter using the AC line.

Kienan


Maxfield Solar
maxfieldso...@hotmail.com<mailto:maxfieldso...@hotmail.com>
(801) 631-5584 (Cell)

From: RE-wrenches  on behalf of Mark 
Frye 
Sent: Sunday, November 3, 2019 11:58 AM
To: re-wrenches@lists.re-wrenches.org 
Subject: Re: [RE-wrenches] Parts List For AC Couple Disconnect


OK, the posts are coming in on the "no" side, but with uncertainty about how 
any given BB inverter might work.


I still think that the BB charger is in charge (no pun) of sending power to the 
battery and if it the battery is at it's set point then the duty cycle on the 
transistors in the rectifier go down - zero. At that point the impedance of the 
AC line would appear to go up. In response the GT inverters would increase 
there output voltage in an attempt to over come the higher impedance.


The voltage monitoring switch that I spec'd has a response delay setting. If I 
am running in offgrid mode, the main worry is voltage sag due to load. So 
generally, the inverter would be running at or below AC voltage set point. 
There may be spikes above voltage set point when a load is disconnected, but I 
could filter that out with the delay on the sensor.


Still, this is why I am asking.


Anyone on the list have more confidence in their understand of BB inverters in 
off-grid mode with AC coupled GT inverters?


Mark


On 11/3/2019 10:44 AM, Kienan Maxfield wrote:
Mark,

I think that you're not understanding what Brian is saying. In any case, your 
proposal will not work with most equipment. There may be some equipment that 
would work that way, but not anything I'm aware of. Let me tell you what will 
happen in a normal system, assuming that the manufacturer hasn't built in an AC 
coupling control mechanism (like frequency shifting)

The BB inverter will maintain a stable AC voltage by allowing the GT inverters 
to back feed into the batteries. If the batteries start overcharging, the BB 
inverter will not raise the AC voltage in response. What will happen instead is 
that there will be no measurable difference in the AC voltage, but the DC 
voltage will continue to rise until it hits the multimode BB inverter's high 
battery cut out voltage, and the BB inverter will shut off, and your entire AC 
line will drop to 0 volts. This will turn off the GT inverter, and as the 
battery voltage falls back into an acceptable range, the BB inverter may or may 
not automatically turn back on. If it does automatically turn back on, then the 
GT inverter will wait for 5 minutes and then they'll start back-feeding until 
the battery voltage goes above the overvoltage setpoint, and the whole system 
shuts off again. So this is what is normally happening if you hear about an AC 
coupling system that shuts off onc

Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Mark Frye]

OK, the posts are coming in on the "no" side, but with uncertainty about 
how any given BB inverter might work.



I still think that the BB charger is in charge (no pun) of sending power 
to the battery and if it the battery is at it's set point then the duty 
cycle on the transistors in the rectifier go down - zero. At that point 
the impedance of the AC line would appear to go up. In response the GT 
inverters would increase there output voltage in an attempt to over come 
the higher impedance.



The voltage monitoring switch that I spec'd has a response delay 
setting. If I am running in offgrid mode, the main worry is voltage sag 
due to load. So generally, the inverter would be running at or below AC 
voltage set point. There may be spikes above voltage set point when a 
load is disconnected, but I could filter that out with the delay on the 
sensor.



Still, this is why I am asking.


Anyone on the list have more confidence in their understand of BB 
inverters in off-grid mode with AC coupled GT inverters?



Mark


On 11/3/2019 10:44 AM, Kienan Maxfield wrote:

Mark,

I think that you're not understanding what Brian is saying. In any 
case, your proposal will not work with most equipment. There may be 
some equipment that would work that way, but not anything I'm aware 
of. Let me tell you what will happen in a normal system, assuming that 
the manufacturer hasn't built in an AC coupling control mechanism 
(like frequency shifting)


The BB inverter will maintain a stable AC voltage by allowing the GT 
inverters to back feed into the batteries. If the batteries start 
overcharging, the BB inverter will not raise the AC voltage in 
response. What will happen instead is that there will be no measurable 
difference in the AC voltage, but the DC voltage will continue to rise 
until it hits the multimode BB inverter's high battery cut out 
voltage, and the BB inverter will shut off, and your entire AC line 
will drop to 0 volts. This will turn off the GT inverter, and as the 
battery voltage falls back into an acceptable range, the BB inverter 
may or may not automatically turn back on. If it does automatically 
turn back on, then the GT inverter will wait for 5 minutes and then 
they'll start back-feeding until the battery voltage goes above the 
overvoltage setpoint, and the whole system shuts off again. So this is 
what is normally happening if you hear about an AC coupling system 
that shuts off once every 6 minutes or so during the day... And yes, I 
have seen a system where the homeowner was told that this was normal, 
and it's just how the system was supposed to work..


So if the inverter has an AC Coupling control mechanism, and that AC 
coupling mode is turned on, then it will change the characteristics of 
the AC line in order to notify the GT inverter to turn off, or to 
decrease its output. The only way that I've ever heard about any 
manufacturers implementing this is through frequency shifting. Now it 
would be perfectly possible to do it through voltage shifting (or 
voltage raising) and I've talked to some engineers who said that on a 
technological level, it wouldn't be any harder for a manufacturer to 
do voltage shifting than frequency shifting, but no manufacturer has 
actually pursued that. So basically, your only options are


 1. use a BB inverter that has frequency shifting control for AC coupling
 2. run a wire from the battery room to the GT inverters that you can
use for controlling them based on the battery voltage
 3. experiment with something custom and just expect a high
probability of eventual failure (but let us know how it goes)
 1. You might be able to find a device that would read the battery
voltage, and then transmit that information wirelessly, then
have another device at the GT inverters that decodes that
information and then drives a relay accordingly. (I have no
idea how to do this, for me, this is in the hypothetical
realm.) Or maybe it could transmit the info via PLC?
 4. or the fourth option is to set the BB inverter's high battery cut
out voltage to just above the absorb voltage and just plan on the
power going out multiple times per sunny day. I wouldn't go for
this one unless it's your own home and you're feeling very
adventuresome.

Essentially the bottom line is that monitoring the AC line will never 
work unless the BB inverter has a built-in AC coupling control 
mechanism, then you'll be monitoring for the frequency rather than the 
voltage.


Sorry for not having anything more helpful to say.
Kienan

*Maxfield Solar*
*maxfieldso...@hotmail.com* <mailto:maxfieldso...@hotmail.com>
*
**(801) 631-5584 (Cell)**
*

*From:* RE-wrenches  on 
behalf of Mark Frye 

*Sent:* Sunday, November 3, 2019 11:00 AM
*To:* re-wrenc

Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Kienan Maxfield]

Mark,

I think that you're not understanding what Brian is saying. In any case, your 
proposal will not work with most equipment. There may be some equipment that 
would work that way, but not anything I'm aware of. Let me tell you what will 
happen in a normal system, assuming that the manufacturer hasn't built in an AC 
coupling control mechanism (like frequency shifting)

The BB inverter will maintain a stable AC voltage by allowing the GT inverters 
to back feed into the batteries. If the batteries start overcharging, the BB 
inverter will not raise the AC voltage in response. What will happen instead is 
that there will be no measurable difference in the AC voltage, but the DC 
voltage will continue to rise until it hits the multimode BB inverter's high 
battery cut out voltage, and the BB inverter will shut off, and your entire AC 
line will drop to 0 volts. This will turn off the GT inverter, and as the 
battery voltage falls back into an acceptable range, the BB inverter may or may 
not automatically turn back on. If it does automatically turn back on, then the 
GT inverter will wait for 5 minutes and then they'll start back-feeding until 
the battery voltage goes above the overvoltage setpoint, and the whole system 
shuts off again. So this is what is normally happening if you hear about an AC 
coupling system that shuts off once every 6 minutes or so during the day... And 
yes, I have seen a system where the homeowner was told that this was normal, 
and it's just how the system was supposed to work..

So if the inverter has an AC Coupling control mechanism, and that AC coupling 
mode is turned on, then it will change the characteristics of the AC line in 
order to notify the GT inverter to turn off, or to decrease its output. The 
only way that I've ever heard about any manufacturers implementing this is 
through frequency shifting. Now it would be perfectly possible to do it through 
voltage shifting (or voltage raising) and I've talked to some engineers who 
said that on a technological level, it wouldn't be any harder for a 
manufacturer to do voltage shifting than frequency shifting, but no 
manufacturer has actually pursued that. So basically, your only options are

  1.  use a BB inverter that has frequency shifting control for AC coupling
  2.  run a wire from the battery room to the GT inverters that you can use for 
controlling them based on the battery voltage
  3.  experiment with something custom and just expect a high probability of 
eventual failure (but let us know how it goes)
 *   You might be able to find a device that would read the battery 
voltage, and then transmit that information wirelessly, then have another 
device at the GT inverters that decodes that information and then drives a 
relay accordingly. (I have no idea how to do this, for me, this is in the 
hypothetical realm.) Or maybe it could transmit the info via PLC?
  4.  or the fourth option is to set the BB inverter's high battery cut out 
voltage to just above the absorb voltage and just plan on the power going out 
multiple times per sunny day. I wouldn't go for this one unless it's your own 
home and you're feeling very adventuresome.

Essentially the bottom line is that monitoring the AC line will never work 
unless the BB inverter has a built-in AC coupling control mechanism, then 
you'll be monitoring for the frequency rather than the voltage.

Sorry for not having anything more helpful to say.
Kienan

Maxfield Solar
maxfieldso...@hotmail.com<mailto:maxfieldso...@hotmail.com>
(801) 631-5584 (Cell)

From: RE-wrenches  on behalf of Mark 
Frye 
Sent: Sunday, November 3, 2019 11:00 AM
To: re-wrenches@lists.re-wrenches.org 
Subject: Re: [RE-wrenches] Parts List For AC Couple Disconnect

OK Brian,

So I think you are confirming that monitoring AC side voltage is an
acceptable way of deciding when to disconnect the GT inverters.

With my parts list, I have a delay time that would hold the GT inverters
off-line for some period of time (I would probably set to 1 hour) before
coming back on line after tipping off.


Mark

On 11/3/2019 9:53 AM, Brian Mehalic wrote:
> With frequency-on/off, frequency power control, or other “inverter 
> integrated” control based on battery voltage/state of charge there is also 
> control in regards to when the ac coupled inverters come back on. And yes, 
> this is definitely needed to prevent overcharge (or get three-stage charging 
> from the  AC coupled system). Of course if it doesn’t work, yes the bus 
> voltage will rise and trip the BB offline.
>
> AC bus voltage will go down as soon as the ac couple inverters are kicked 
> off, so if that’s your measured value unless your control system has a delay 
> or other component to control reconnection and charging i think it could 
> essentially chatter off and on and off and...
>
> Bri

Re: [RE-wrenches] Parts List For AC Couple Disconnect

[William Miller]

Mark:



I do not think line voltage is an appropriate criteria for controlling an
AC coupled system for these reasons:

1.   My understanding of how an AC coupled system works does not match
yours.  The concept is still black magic to me, but as I understand it,
when you use GT inverters to charge batteries through a battery inverter,
there is no charge control.  This is the essence of this problem.  The
batteries will over-charge if you do not intervene.  Remember, in an AC
coupled system you are charging batteries by running power *into* the
*output* of the battery inverter, or backwards to the normal power flow.  I
understand this is why the normal charge control system does not work.

2.   If the battery charging does not stop, there can be no cause and
effect that will cause line voltage to rise.

3.   Even if 2 above were not true, batteries, as they approach full
charge, taper their use of charging source, so you cannot expect any
significant change in charge current when charging stops.

4.   There are too many other factors that can affect line voltage.  If
you set some circuit to do something when live voltage changes beyond a
certain thresholds, this trigger will happen randomly as line voltage
changes for external reasons.



I hate to break the news, but you need to find some way to communicate the
battery voltage to the GT inverter output.  You don’t have to run the GT
inverter AC output all the way to the battery inverter panel, but you will
need to get a control signal connection between the two systems.



Caveat:  I don’t pretend to know thoroughly about how AC coupled systems
work, but this is how I understand them.  Maybe others can verify my
conclusions.



William





Miller Solar

17395 Oak Road, Atascadero, CA 93422

805-438-5600

www.millersolar.com

CA Lic. 773985



-Original Message-
From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On
Behalf Of Mark Frye
Sent: Sunday, November 3, 2019 9:39 AM
To: re-wrenches@lists.re-wrenches.org
Subject: Re: [RE-wrenches] Parts List For AC Couple Disconnect



Hi William,



Thanks, you bring up issues that are important to me here.



In particular, my situation is that the GT inverter is inter-tied a

couple sub panels upstream of where I want to put the BB inverter. The

distance is long, so I am looking for a solution where I don't have to

run a cable between the two.



In general, I do wonder about using AC line voltage rise to take the Gt

inverters off line. The main goal is to prevent excess voltage at the

battery, so monitoring battery voltage is most direct, and there are

simple solutions for that.



Is AC line voltage a suitable metric for achieving the same goal?



Here is where I could use Wrench knowledge to confirm my thinking, that

being:



- With excess energy in the system, the charger moves it into the

battery, raising it's voltage until it reaches it high charging voltage

set point



- Once the battery reaches it's high voltage set point, the charger

stops putting energy into the battery



- With no other place to put the excess energy, the AC voltage rises



Am I getting this right, the reason to disconnect AC coupled inverters

when the battery if full is not to prevent the batteries from being

overcharged, but rather to prevent the AC line from becoming unstable?



I am hoping this is correct and that with $200 of industrial grade

devices from Digikey I can implement a robust control that will

disconnect the GT inverters before the AC line goes so high that the BB

inverter faults.



Mark







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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Dave Angelini Offgrid Solar]

Marc, High or low battery cut-out on a battery based inverter is lights
out. There is usually a warning period that becomes a fault. I still think
this is crazy for offgrid unless it is a very large system 20+KW of battery
inverters in a microgrid type mindset with onsight knowledgeable people.
Also lots of DC coupled solar.

Forgive me if I have missed something here as I have installed about 20
gensets for my California wildfire residents last month. Good Luck.

Dave Angelini Offgrid Solar
"we go where powerlines don't"
http://members.sti.net/offgridsolar/
e-mail offgridso...@sti.net
text 209 813 0060

On Sun, 3 Nov 2019 09:38:51 -0800, Mark Frye 
wrote:
> Hi William,
> 
> Thanks, you bring up issues that are important to me here.
> 
> In particular, my situation is that the GT inverter is inter-tied a 
> couple sub panels upstream of where I want to put the BB inverter. The 
> distance is long, so I am looking for a solution where I don't have to 
> run a cable between the two.
> 
> In general, I do wonder about using AC line voltage rise to take the Gt 
> inverters off line. The main goal is to prevent excess voltage at the 
> battery, so monitoring battery voltage is most direct, and there are 
> simple solutions for that.
> 
> Is AC line voltage a suitable metric for achieving the same goal?
> 
> Here is where I could use Wrench knowledge to confirm my thinking, that 
> being:
> 
> - With excess energy in the system, the charger moves it into the 
> battery, raising it's voltage until it reaches it high charging voltage 
> set point
> 
> - Once the battery reaches it's high voltage set point, the charger 
> stops putting energy into the battery
> 
> - With no other place to put the excess energy, the AC voltage rises
> 
> Am I getting this right, the reason to disconnect AC coupled inverters 
> when the battery if full is not to prevent the batteries from being 
> overcharged, but rather to prevent the AC line from becoming unstable?
> 
> I am hoping this is correct and that with $200 of industrial grade 
> devices from Digikey I can implement a robust control that will 
> disconnect the GT inverters before the AC line goes so high that the BB 
> inverter faults.
> 
> Mark
> 
> 
> 
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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Brian Mehalic]

More like “could work let us know how it goes!”

Brian

> On Nov 3, 2019, at 10:01 AM, Mark Frye  wrote:
> 
> OK Brian,
> 
> So I think you are confirming that monitoring AC side voltage is an 
> acceptable way of deciding when to disconnect the GT inverters.
> 
> With my parts list, I have a delay time that would hold the GT inverters 
> off-line for some period of time (I would probably set to 1 hour) before 
> coming back on line after tipping off.
> 
> 
> Mark
> 
>> On 11/3/2019 9:53 AM, Brian Mehalic wrote:
>> With frequency-on/off, frequency power control, or other “inverter 
>> integrated” control based on battery voltage/state of charge there is also 
>> control in regards to when the ac coupled inverters come back on. And yes, 
>> this is definitely needed to prevent overcharge (or get three-stage charging 
>> from the  AC coupled system). Of course if it doesn’t work, yes the bus 
>> voltage will rise and trip the BB offline.
>> 
>> AC bus voltage will go down as soon as the ac couple inverters are kicked 
>> off, so if that’s your measured value unless your control system has a delay 
>> or other component to control reconnection and charging i think it could 
>> essentially chatter off and on and off and...
>> 
>> Brian
>> 
 On Nov 3, 2019, at 9:38 AM, Mark Frye  wrote:
>>> 
>>> Hi William,
>>> 
>>> Thanks, you bring up issues that are important to me here.
>>> 
>>> In particular, my situation is that the GT inverter is inter-tied a couple 
>>> sub panels upstream of where I want to put the BB inverter. The distance is 
>>> long, so I am looking for a solution where I don't have to run a cable 
>>> between the two.
>>> 
>>> In general, I do wonder about using AC line voltage rise to take the Gt 
>>> inverters off line. The main goal is to prevent excess voltage at the 
>>> battery, so monitoring battery voltage is most direct, and there are simple 
>>> solutions for that.
>>> 
>>> Is AC line voltage a suitable metric for achieving the same goal?
>>> 
>>> Here is where I could use Wrench knowledge to confirm my thinking, that 
>>> being:
>>> 
>>> - With excess energy in the system, the charger moves it into the battery, 
>>> raising it's voltage until it reaches it high charging voltage set point
>>> 
>>> - Once the battery reaches it's high voltage set point, the charger stops 
>>> putting energy into the battery
>>> 
>>> - With no other place to put the excess energy, the AC voltage rises
>>> 
>>> Am I getting this right, the reason to disconnect AC coupled inverters when 
>>> the battery if full is not to prevent the batteries from being overcharged, 
>>> but rather to prevent the AC line from becoming unstable?
>>> 
>>> I am hoping this is correct and that with $200 of industrial grade devices 
>>> from Digikey I can implement a robust control that will disconnect the GT 
>>> inverters before the AC line goes so high that the BB inverter faults.
>>> 
>>> Mark
>>> 
>>> 
>>> 
>>> ___
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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Brian Mehalic]

Hey now I didn’t say that!

Brian

> On Nov 3, 2019, at 10:01 AM, Mark Frye  wrote:
> 
> OK Brian,
> 
> So I think you are confirming that monitoring AC side voltage is an 
> acceptable way of deciding when to disconnect the GT inverters.
> 
> With my parts list, I have a delay time that would hold the GT inverters 
> off-line for some period of time (I would probably set to 1 hour) before 
> coming back on line after tipping off.
> 
> 
> Mark
> 
>> On 11/3/2019 9:53 AM, Brian Mehalic wrote:
>> With frequency-on/off, frequency power control, or other “inverter 
>> integrated” control based on battery voltage/state of charge there is also 
>> control in regards to when the ac coupled inverters come back on. And yes, 
>> this is definitely needed to prevent overcharge (or get three-stage charging 
>> from the  AC coupled system). Of course if it doesn’t work, yes the bus 
>> voltage will rise and trip the BB offline.
>> 
>> AC bus voltage will go down as soon as the ac couple inverters are kicked 
>> off, so if that’s your measured value unless your control system has a delay 
>> or other component to control reconnection and charging i think it could 
>> essentially chatter off and on and off and...
>> 
>> Brian
>> 
 On Nov 3, 2019, at 9:38 AM, Mark Frye  wrote:
>>> 
>>> Hi William,
>>> 
>>> Thanks, you bring up issues that are important to me here.
>>> 
>>> In particular, my situation is that the GT inverter is inter-tied a couple 
>>> sub panels upstream of where I want to put the BB inverter. The distance is 
>>> long, so I am looking for a solution where I don't have to run a cable 
>>> between the two.
>>> 
>>> In general, I do wonder about using AC line voltage rise to take the Gt 
>>> inverters off line. The main goal is to prevent excess voltage at the 
>>> battery, so monitoring battery voltage is most direct, and there are simple 
>>> solutions for that.
>>> 
>>> Is AC line voltage a suitable metric for achieving the same goal?
>>> 
>>> Here is where I could use Wrench knowledge to confirm my thinking, that 
>>> being:
>>> 
>>> - With excess energy in the system, the charger moves it into the battery, 
>>> raising it's voltage until it reaches it high charging voltage set point
>>> 
>>> - Once the battery reaches it's high voltage set point, the charger stops 
>>> putting energy into the battery
>>> 
>>> - With no other place to put the excess energy, the AC voltage rises
>>> 
>>> Am I getting this right, the reason to disconnect AC coupled inverters when 
>>> the battery if full is not to prevent the batteries from being overcharged, 
>>> but rather to prevent the AC line from becoming unstable?
>>> 
>>> I am hoping this is correct and that with $200 of industrial grade devices 
>>> from Digikey I can implement a robust control that will disconnect the GT 
>>> inverters before the AC line goes so high that the BB inverter faults.
>>> 
>>> Mark
>>> 
>>> 
>>> 
>>> ___
>>> List sponsored by Redwood Alliance
>>> 
>>> List Address: RE-wrenches@lists.re-wrenches.org
>>> 
>>> Change listserver email address & settings:
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>>> www.members.re-wrenches.org
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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Mark Frye]

OK Brian,

So I think you are confirming that monitoring AC side voltage is an 
acceptable way of deciding when to disconnect the GT inverters.


With my parts list, I have a delay time that would hold the GT inverters 
off-line for some period of time (I would probably set to 1 hour) before 
coming back on line after tipping off.



Mark

On 11/3/2019 9:53 AM, Brian Mehalic wrote:

With frequency-on/off, frequency power control, or other “inverter integrated” 
control based on battery voltage/state of charge there is also control in 
regards to when the ac coupled inverters come back on. And yes, this is 
definitely needed to prevent overcharge (or get three-stage charging from the  
AC coupled system). Of course if it doesn’t work, yes the bus voltage will rise 
and trip the BB offline.

AC bus voltage will go down as soon as the ac couple inverters are kicked off, 
so if that’s your measured value unless your control system has a delay or 
other component to control reconnection and charging i think it could 
essentially chatter off and on and off and...

Brian


On Nov 3, 2019, at 9:38 AM, Mark Frye  wrote:

Hi William,

Thanks, you bring up issues that are important to me here.

In particular, my situation is that the GT inverter is inter-tied a couple sub 
panels upstream of where I want to put the BB inverter. The distance is long, 
so I am looking for a solution where I don't have to run a cable between the 
two.

In general, I do wonder about using AC line voltage rise to take the Gt 
inverters off line. The main goal is to prevent excess voltage at the battery, 
so monitoring battery voltage is most direct, and there are simple solutions 
for that.

Is AC line voltage a suitable metric for achieving the same goal?

Here is where I could use Wrench knowledge to confirm my thinking, that being:

- With excess energy in the system, the charger moves it into the battery, 
raising it's voltage until it reaches it high charging voltage set point

- Once the battery reaches it's high voltage set point, the charger stops 
putting energy into the battery

- With no other place to put the excess energy, the AC voltage rises

Am I getting this right, the reason to disconnect AC coupled inverters when the 
battery if full is not to prevent the batteries from being overcharged, but 
rather to prevent the AC line from becoming unstable?

I am hoping this is correct and that with $200 of industrial grade devices from 
Digikey I can implement a robust control that will disconnect the GT inverters 
before the AC line goes so high that the BB inverter faults.

Mark



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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Brian Mehalic]

With frequency-on/off, frequency power control, or other “inverter integrated” 
control based on battery voltage/state of charge there is also control in 
regards to when the ac coupled inverters come back on. And yes, this is 
definitely needed to prevent overcharge (or get three-stage charging from the  
AC coupled system). Of course if it doesn’t work, yes the bus voltage will rise 
and trip the BB offline. 

AC bus voltage will go down as soon as the ac couple inverters are kicked off, 
so if that’s your measured value unless your control system has a delay or 
other component to control reconnection and charging i think it could 
essentially chatter off and on and off and...

Brian

> On Nov 3, 2019, at 9:38 AM, Mark Frye  wrote:
> 
> Hi William,
> 
> Thanks, you bring up issues that are important to me here.
> 
> In particular, my situation is that the GT inverter is inter-tied a couple 
> sub panels upstream of where I want to put the BB inverter. The distance is 
> long, so I am looking for a solution where I don't have to run a cable 
> between the two.
> 
> In general, I do wonder about using AC line voltage rise to take the Gt 
> inverters off line. The main goal is to prevent excess voltage at the 
> battery, so monitoring battery voltage is most direct, and there are simple 
> solutions for that.
> 
> Is AC line voltage a suitable metric for achieving the same goal?
> 
> Here is where I could use Wrench knowledge to confirm my thinking, that being:
> 
> - With excess energy in the system, the charger moves it into the battery, 
> raising it's voltage until it reaches it high charging voltage set point
> 
> - Once the battery reaches it's high voltage set point, the charger stops 
> putting energy into the battery
> 
> - With no other place to put the excess energy, the AC voltage rises
> 
> Am I getting this right, the reason to disconnect AC coupled inverters when 
> the battery if full is not to prevent the batteries from being overcharged, 
> but rather to prevent the AC line from becoming unstable?
> 
> I am hoping this is correct and that with $200 of industrial grade devices 
> from Digikey I can implement a robust control that will disconnect the GT 
> inverters before the AC line goes so high that the BB inverter faults.
> 
> Mark
> 
> 
> 
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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Mark Frye]

Hi William,

Thanks, you bring up issues that are important to me here.

In particular, my situation is that the GT inverter is inter-tied a 
couple sub panels upstream of where I want to put the BB inverter. The 
distance is long, so I am looking for a solution where I don't have to 
run a cable between the two.


In general, I do wonder about using AC line voltage rise to take the Gt 
inverters off line. The main goal is to prevent excess voltage at the 
battery, so monitoring battery voltage is most direct, and there are 
simple solutions for that.


Is AC line voltage a suitable metric for achieving the same goal?

Here is where I could use Wrench knowledge to confirm my thinking, that 
being:


- With excess energy in the system, the charger moves it into the 
battery, raising it's voltage until it reaches it high charging voltage 
set point


- Once the battery reaches it's high voltage set point, the charger 
stops putting energy into the battery


- With no other place to put the excess energy, the AC voltage rises

Am I getting this right, the reason to disconnect AC coupled inverters 
when the battery if full is not to prevent the batteries from being 
overcharged, but rather to prevent the AC line from becoming unstable?


I am hoping this is correct and that with $200 of industrial grade 
devices from Digikey I can implement a robust control that will 
disconnect the GT inverters before the AC line goes so high that the BB 
inverter faults.


Mark



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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[William Miller]

Mark:



I think the task is to measure battery voltage and, if it gets too high,
generate a signal to disconnect the AC coupled feed to the AC bus.
Therefore the sample is DC, not AC.  Simple matter of voltage dividing into
an acceptable range.



I submit that there are probably a lot of ways to skin this cat.  For
example a Trace C40 charge controller in diversion mode should give you a
high state signal to open an AC relay on the grid-tied inverter AC output:



BatteryàC40 in diversionàRelay on output of GT inverter



The question is, what application is robust enough to allow adequate
confidence?  Some people with experience can “roll-their-own” and build
solid assemblies that can handle the rigors of field use.  If I am applying
a solution to a remote site with a high requirement for reliability, I am
looking for professionally manufactured off-the-shelf equipment.  At home,
I can Rube Goldberg as much as I want.



William



*From:* RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On
Behalf Of *Mark Frye
*Sent:* Saturday, November 2, 2019 7:32 PM
*To:* re-wrenches@lists.re-wrenches.org
*Subject:* Re: [RE-wrenches] Parts List For AC Couple Disconnect



Glenn,

OK, while I would prefer to not get into compiling code onto an ARM, my
main question would be, how do you get the voltage value into the Arduino?

Rectify the AC voltage and then voltage divide down to the chip input pin?

Mark

On 11/2/2019 10:14 AM, Glenn Burt wrote:

Sounds like a job for an Arduino...



-Glenn

Sent from my 'smart'phone, so please excuse typos and spelling errors.



-- Original message--

*From: *Mark Frye

*Date: *Sat, Nov 2, 2019 1:05 PM

*To: *re-wrenches@lists.re-wrenches.org;

*Cc: *

*Subject:*[RE-wrenches] Parts List For AC Couple Disconnect



Folks,



Can anyone share a parts list for setting up a AC couple disconnect?



I want to couple a

 non-frequency response grid-tied inverter to a

battery based stand-alone inverter.



I have only 8 amps output from the GT inverters, so can use 10A relay

contacts.



I want a device to monitor AC voltage and latch a coil on when it raises

above a set point (250VAC). I then want a timer to release the latch

after about 1 hour.



Sound about right? Are any vendors selling such a device? How about a

parts list from Digikey?



Thanks,



Mark Frye



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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Mark Frye]

Glenn,

OK, while I would prefer to not get into compiling code onto an ARM, my 
main question would be, how do you get the voltage value into the Arduino?


Rectify the AC voltage and then voltage divide down to the chip input pin?

Mark

On 11/2/2019 10:14 AM, Glenn Burt wrote:

Sounds like a job for an Arduino...

-Glenn
Sent from my 'smart'phone, so please excuse typos and spelling errors.

-- Original message--
*From: *Mark Frye
*Date: *Sat, Nov 2, 2019 1:05 PM
*To: *re-wrenches@lists.re-wrenches.org 
;

*Cc: *
*Subject:*[RE-wrenches] Parts List For AC Couple Disconnect

Folks,

Can anyone share a parts list for setting up a AC couple disconnect?

I want to couple a
  non-frequency response grid-tied inverter to a
battery based stand-alone inverter.

I have only 8 amps output from the GT inverters, so can use 10A relay
contacts.

I want a device to monitor AC voltage and latch a coil on when it raises
above a set point (250VAC). I then want a timer to release the latch
after about 1 hour.

Sound about right? Are any vendors selling such a device? How about a
parts list from Digikey?

Thanks,

Mark Frye

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Re: [RE-wrenches] Parts List For AC Couple Disconnect

[Glenn Burt]

Sounds like a job for an Arduino...-GlennSent from my 'smart'phone, so please 
excuse typos and spelling errors.-- Original message--From: Mark 
FryeDate: Sat, Nov 2, 2019 1:05 PMTo: re-wrenches@lists.re-wrenches.org;Cc: 
Subject:[RE-wrenches] Parts List For AC Couple DisconnectFolks,

Can anyone share a parts list for setting up a AC couple disconnect?

I want to couple a non-frequency response grid-tied inverter to a 
battery based stand-alone inverter.

I have only 8 amps output from the GT inverters, so can use 10A relay 
contacts.

I want a device to monitor AC voltage and latch a coil on when it raises 
above a set point (250VAC). I then want a timer to release the latch 
after about 1 hour.

Sound about right? Are any vendors selling such a device? How about a 
parts list from Digikey?

Thanks,

Mark Frye

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