Re: [RE-wrenches] "Re-powering" Aging Utilty Scale PV systems

2021-09-11 Thread drake . chamberlin 

I've been following this string with interest. The maintenance of decade
old systems is important, as the modules are warrantied for 25 years.
This duration is often considered in payback expectations. 


What actually fails in the utility scale inverters? Is the failure
catastrophic, or do relays or some boards fail? How much of the inverter
is compromised? 


Is there any hope that at least some of these could be put back into
service by experienced electronic technicians? 

Drake 

Drake Chamberlin 

Athens Electric LLC 

Ohio Electrical Contractor's License 44810 

CO Master Electrician's License 4526 


NABCEP Certified PV Installation Professional ---

On 2021-09-08 17:45, William Miller wrote:





Friends: 

I learned a new buzzword recently:  "Re-powering."  It means replacing inverters on an existing PV system of ten or more years old.  Due to the high number of systems of this vintage it appears that re-powering has become somewhat of a sub-industry.  The big problem is these systems are all 600 Volt  limited PV panels, combiners and re-combiners and there are no 600 volt utility grade inverters being manufactured. 

I am working on a utility scale system [1] built about 14 years ago that fits the description above.  There are two 250KVA Xantrex GT250 inverters and one has failed.  The question of the moment is:  Repair or replace? 

Repair:  If we fix these inverters, can we count on support in the future?We can negotiate a service contract with Schneider at a cost yet to be revealed.  This requires we buy a spare parts kit for about $100K.  There are a few other companies that claim to offer repair services on these inverters but none has followed through. 

Replace:  The PV plant is built with panels and BOS all limited to 600 VDC max.  There are no more 600 volt input utility scale inverters being built, or at least none that I have found.  If we install a 1000 or 1500 volt inverter we may have to replace the entire PV array and BOS.  It may be possible to convert the output of the existing panels to a higher voltage with DC-DC converters.  

Here are the options I see: 

Optimizers: One purveyor of optimizers is Solar Edge.  Solar Edge offers a 100 KVA inverter.  This inverter requires DC input of 850 volts.  The inverter requires optimizers to obtain this voltage.  The question:  Do the optimizers isolate the PV from the higher string voltages in the case of a catastrophic failure of one or more of the optimizers? 

Repower with outboard DC-DC voltage converters, such as provided by Alencon Systems.  Solectria has successfully done this.  Here [2] is a paper on the subject. 

If anyone has dealt with this issue before I would sure appreciate any wisdom. 

Here is a link [3] to a web-page I built for this project. 

Thanks, 

William Miller 

Miller Solar 

17395 Oak Road, Atascadero, CA 93422 

805-438-5600 

www.millersolar.com [4] 

CA Lic. 773985 


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Links:
--
[1]
https://millersolar.com/MillerSolar/Portfolio/Commercial/CommercialTracker/CommercialTracker.html
[2]
https://alenconsystems.com/learning/pv-retrofits-with-transformerless-inverters/
[3]
https://millersolar.com/MillerSolar/case_studies/30-Re-Powering/re-powering.html
[4] http://www.millersolar.com/___
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[RE-wrenches] FW: "Re-powering" Aging Utilty Scale PV systems

2021-09-11 Thread William Miller 
Wrenches:



Here is our answer.  The logic is not what I anticipated but it works for
me.



Interesting that there is still a need to list inverters to provide zero
backfeed current.  This is necessary if you want to avoid fuses on two
string installations.



William



Miller Solar

17395 Oak Road, Atascadero, CA 93422

805-438-5600

www.millersolar.com

CA Lic. 773985





*From:* Jeff Laughy [mailto:jeff.lau...@solaredge.com]
*Sent:* Friday, September 10, 2021 1:35 PM
*To:* Ryan Suchsland; Garrett Duffy; Jonathan Smith; will...@millersolar.com
*Subject:* RE: [RE-wrenches] "Re-powering" Aging Utilty Scale PV systems



Hello William,



As part of the UL-1741 listing process, SolarEdge inverters are verified to
provide zero back feed current to the input source circuits



SolarEdge inverters are non-isolated, transformer-less, so the PV array
needs to operate in an ungrounded floating state. The fixed DC string
voltage for our 480 volt 3 phase inverters is 850 Vdc. Since the array is
ungrounded, the highest voltage to ground measured anywhere on the string
at the optimizer input connectors would be 425 Vdc. For this reason it is
safe to use PV modules rated at 600 volts.



Best Regards



Jeff Laughy

Principal Engineer
M  +1-209-607-2402
jeff.lau...@solaredge.com

[image: cid:image001.gif@01D495F8.2A2123F0] 


* *[image: Diagram Description
automatically generated with low confidence]










*From:* Ryan Suchsland 
*Sent:* Thursday, September 9, 2021 4:50 PM
*To:* Garrett Duffy ; Jonathan Smith <
jonathan.sm...@solaredge.com>
*Cc:* Jeff Laughy 
*Subject:* RE: [RE-wrenches] "Re-powering" Aging Utilty Scale PV systems



Hi all,



I had a conversation with the customer earlier basically just to address
his question, so I think it would be helpful to pull in Jeff here to help
answer the questions.



*Ryan Suchsland*

Inside Sales Account Executive

O: 510-897-8000 ext. 2180

M: 602-694-9570

Customer service & tech support 510-498-3200



ryan.suchsl...@solaredge.com





*From:* Garrett Duffy 
*Sent:* Thursday, September 9, 2021 12:49 PM
*To:* Ryan Suchsland ; Jonathan Smith <
jonathan.sm...@solaredge.com>
*Cc:* Jeff Laughy 
*Subject:* RE: [RE-wrenches] "Re-powering" Aging Utilty Scale PV systems



Removing customer.



Ryan / John – do we need to pull in Jeff to review this? What is the status
so we aren’t all working on this?



Thank you,



Garrett Duffy

Channel Sales Manager – Central/Midwest

garrett.du...@solaredge.com

T: +1-510-552-7326

 [image: id:image001.gif@01D495F3.28951F00]








*From:* William Miller 
*Sent:* Thursday, September 9, 2021 10:05 AM
*To:* August Goers 
*Cc:* RE-wrenches ; Greg Notley <
g...@powercomengineering.com>; Jonathan Smith ;
Ryan Suchsland ; Garrett Duffy <
garrett.du...@solaredge.com>
*Subject:* RE: [RE-wrenches] "Re-powering" Aging Utilty Scale PV systems



August:



I am not worried about the inverter backfeeding.  I only brought that up
because there was a precedent set that in order to rule out an electronic
assembly backfeeding, it had to be listed as such.



Here is what I am worried about:  I am worried about the high voltage on
the output of an optimizer crossing over the optimizer in a failure
condition and energizing the input circuit of the optimizer.



If I understand the design process correctly, manufacturing to high
standards is not enough—a listing with a recognized agency to that effect
is also required.



Thanks again for thinking and writing about this.  Your experience and
expertise is valued.



William



Miller Solar

17395 Oak Road, Atascadero, CA 93422

805-438-5600

www.millersolar.com


CA Lic. 773985





*From:* August Goers [mailto:aug...@luminalt.com]
*Sent:* Thursday, September 9, 2021 9:34 AM
*To:* William Miller
*Cc:* RE-wrenches; Greg Notley; jonathan.sm...@solaredge.com;
rya...@solaredge.com; Garrett Duffy
*Subject:* Re: [RE-wrenches] "Re-powering" Aging Utilty Scale PV systems



Hi William - I think I'm picking up on a couple of separate issues here.
First, the question is whether you can install a module rated for 600 VDC
max on a 1000 VDC SolarEdge system. I realize that the article I linked to
was talking about string combiners and currents, but the isolation between
the module side and output side of the optimizer was the point. The max
input voltage on the optimizers is less than 100 VDC, so it would seem safe
to connect a