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 <https://millersolar.com/MillerSolar/Portfolio/Commercial/CommercialTracker/CommercialTracker.html> 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 <https://alenconsystems.com/learning/pv-retrofits-with-transformerless-inverters/> is a paper on the subject. If anyone has dealt with this issue before I would sure appreciate any wisdom. Here is a link <https://millersolar.com/MillerSolar/case_studies/30-Re-Powering/re-powering.html> 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 CA Lic. 773985
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