By combining the dc combiner box, dc disconnects and inverter into one enclosure can be especially profitable in re-powering situations where there has been noticeable corrosion in combiner boxes and at dc disconnect switches / fusing within the array field.

2022 Top Article - New Solis 1000 Vdc / 480 Vac PV String Inverters

Article from | Solis Inverters

It was not Solis’ intention to design such an impressive inverter for the re-powering market.  The new Solis 75-100 kW PV string inverter family was meant to continue the Solis tradition of multiple, independent MPPTs with very wide operating ranges.  It was the full power MPPT operating range that spanned across typical 600 Vdc PV array string voltages (as low as 308 Vdc on the Solis 90 kW inverter) that was the unexpected capability that attracted the re-powering market.  In this article, we will focus on the largest inverter in the lineup, the 100 kW.

New Solis 1000 Vdc / 480 Vac PV string inverters, updated with the UL 1741 SB certification in 2022, will be familiar to Solis installers but include new features and new solutions that will add profit to the bottom line by reducing material costs and time on site.  

The Solis 100 kW PV string inverter is a 1000 Vdc / 480 Vac product with ten (10) dual-input, independent MPPTs and five (5) segmented, lock out / tag out dc switches.  Installers can design for +1.5/1.0 dc/ac ratios and utilize the largest PV modules available today.  This Solis family of products includes 75 kW, 80 kW, 90 kW and 100 kW PV string inverters.  They all feature new Solis AFCI firmware that reduces false alarms and identifies the fault at the PV string level.  They include NEMA 4X enclosures, Type II dc/ac surge protection, leakage current suppression, and redundant heat sink + fan cooling.   Solis inverters are dual stage inverters to maximize reliability and kWhr production.  Operations and maintenance are under control with a redundant ac/dc inverter power supply, remote monitoring down to the PV string level, remote firmware / software updates, and remote control of the inverter(s) including remote-start of fast (<1 hour) IV Curve Scanning.

Like many other industries, supply chain issues are negatively affecting the PV industry.  With Solis, you can count on a financially strong manufacturing company that leverages long term relationships with component suppliers to ensure inverter quality and a steady supply of product from the new Ginlong Technologies factories in Ningbo China, expanded to 20 GW annual in 2022.  We are excited to announce the latest factory expansion to 40 GW annual will be fully operational by Q4 2022.  

In addition to availability, PV EPC firms are looking for PV system equipment and designs that will reduce material costs and labor time.  Recent studies* show PV string inverter systems have lower CAPEX cost compared to other commercial 1000 Vdc PV system types, e.g., dc power optimizer or micro-inverter systems.  North American PV system installers have come to depend on the reliable, trouble-free performance of Solis inverters and communication systems to fulfill this promise.  New communication tools, like the new Wi-Fi / LAN Stick can be used with the familiar external, touch-safe comm port on all Solis inverters.  For added flexibility, installers can daisy-chain inverters together with CAT6 cable or Beldon cable connected to terminals within the wiring box of the inverter.  With the Solis Modbus map (under NDA), a wide variety of communication platforms can be utilized at Solis inverter installation sites.  

Installers may notice a new designation in the 75-100 kW inverter model names.  Solis installers across North America have seen how PV modules are getting larger and more powerful, with operating voltages near 40 VDC and amp output exceeding 17 amps on the latest +600 Watt PV modules.  Solis has updated the 75-100 kW inverters with the -PLUS designation in recognition of the need for PV string inputs to have higher ampacity, e.g., Solis-100K-5G-US-RSS-PLUS.  This inverter has a factory-integrated Tigo PLC signal transmitter (-RSS) and it has higher ampacity dc terminals (-PLUS).  

Solis 100 kW PV string inverters save installers money by combining the dc combiner box, dc disconnects and inverter into one enclosure.  This can be especially profitable in re-powering situations where there has been noticeable corrosion in combiner boxes and at dc disconnect switches / fusing within the array field.  It may make a lot of sense to re-power a site if the PV system is on valuable land, or there is a favorable interconnection and/or off-taker agreement in place.  But technicians must do their due diligence on the PV array.  

The PV modules must be assessed for normal PV cell degradation (typically less than 5% for PV arrays less than 10 years old).  Technicians must especially evaluate any UV or environmental pressures on the PV array source circuits and output circuits.  This assessment could make or break the financials of a re-powering bid.  A Megger test is useful for ensuring the PV array wiring will not be the cause of excessive AFCI alarms from the new inverters.  But if the PV array wiring has been covered and is in good shape, re-powering system designers can replace the combiner boxes and dc disconnects / fusing in the field, along with the older inverter with a single product, the Solis 100K PV string inverter with 20 inputs on 10 MPPTs.  The original PV output circuit wiring could be recycled as inverter ac output conductors.   

At new PV system sites, high power and amp ratings (-PLUS = 30 amp) at the Solis inverter MPPT inputs allow installers to Y-Connect two PV strings in the array field and reduce the PV output circuits brought to the inverter.  Each MPPT input at the inverter can handle 100% of the MPPT full power rating.  This wiring technique will save copper costs on the dc side of the system.  On the ac side, no neutral is required, installers run L1, L2, L3 and Ground.  Solis terminals are bi-metallic allowing installers to run large aluminum conductors and save money on ac wire runs.

The new Solis PV string inverters, certified to IEEE 1547-2018 and tested to the UL 1741 SB test standard, are flexible and high-performance PV string inverters that can be utilized on legacy 600 Vdc PV arrays or on 1000 Vdc rooftop PV systems where site owners are looking for inverters that deliver best LCOE or can be configured at high dc/ac ratios to optimize an asset’s internal rate of return (IRR).  Either way, the new 75-100 kW inverters from Solis will surprise you with their unexpected capability to re-power 600 Vdc sites as well as deliver solid financial / performance goals on any new rooftop system (across all US utility jurisdictions) that require modern grid interoperability and the latest safety and performance features.

If you have any questions, please reach out to the US Solis Support team for assistance: email: & phone: +1(866)438-8408







* U.S. Solar Photovoltaic System and Energy Storage Cost Benchmark: Q1 2020 David Feldman, Vignesh Ramasamy, Ran Fu, Ashwin Ramdas, Jal Desai, and Robert Margolis.  National Renewable Energy Laboratory (NREL), Technical Report NREL/TP-6A20-77324 January 2021

The content & opinions in this article are the author’s and do not necessarily represent the views of AltEnergyMag

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