In the past, a fault in a central inverter could mean significant power loss on a solar array. These inverters used in large-scale solar projects convert huge amounts of energy in a single unit. Inverter manufacturer Sungrow is addressing fault issues in central inverters by making their components modular and more approachable for repairs. Today, we’re joined by Daniel Friberg, director of product engineering at Sungrow, to discuss the company’s latest central inverter model and what that will mean for solar array uptime.
What is the footprint of the new SG4400UD-MV station and what does it include?
We have been able to stay basically with the same footprint as we’ve had in previous generations over the last five, six years. So it’s a standard shipping container format. It’s 8 ft wide by 20 ft long. Its height is a standard format, so it’s 9 ft 6 in. tall. Basically, we’ve been able to increase the power with this new model to 4,400 kVA vs. the old 3,600 kVA, so a 20% increase in this same footprint.
The unit is a complete skid which it includes a medium-voltage transformer for connection to 35.5 kV, as well as the power conversion system — the inverter. And we also have an auxiliary power unit, which could either be a 5 kVA or a 40 kVA optional unit depending on what you power as far as trackers and weather station, switches, etc.
So, the new Sungrow inverter is “modular.” Can you explain this further?
Traditionally, our inverters have been a single large inverter, which also makes it somewhat sensitive to in case you have an internal fault. You basically would lose that whole complete unit. What we have done now in this latest generation is we have split the unit up into four identical 1.1 kVA modules. So in total 4,400 V. But what this gives us is basically partial redundancy, so in case, for example, you have a single cooling fan fault, in the whole unit it would take down the complete 3.6 MW. In this case, you would basically just lose 25% or just 1.1 MW.
That is an improvement for the reliability and the uptime on the site. We also have the option to size the system a little bit different. We have the option now for a three-module unit. That would basically be a 3.3-MW system, which could be useful in certain corner cases.
Also, with four independent units, we have four MPPTs. We have a single MPPT, or maximum power point tracker, in the past unit, and the advantage of having more of these is that you can have potentially uneven terrain, where you know there is some shading and some things like that. You can further optimize it now when you have multiple MPPTs.
Are there any performance differences in the SG4400 when compared to previous inverters?
We have improved the processing power. So we basically have a more powerful CPU in the new unit. This will lead to an increase in performance when it comes to response time. For example, reactive response time is less than 20 milliseconds or simply almost a single-cycle response compared to multiple cycles in past generations of product. So that whole area of improved power support and grid support functionality is something that has been improved. It also comes with direct compliance with the IEEE 1547-2018. It’s also prepared for the new IEEE standards that are coming out, which is the IEEE 2800.
Sungrow describes the new SG4400 inverter as having easier O&M considerations. Can you explain why?
We talked earlier about the modular approach. This doesn’t only go for the main inverter itself, but also internally in each section more modularity has been achieved. What this means is that when you remove, for example you have a semiconductor fault, you can remove that whole package and it is just basically a unit you remove and slide it out. Or if you have a fan issue, you replace the full cooling fan package. So there’s no need to go in individually and do a certain part. We’ve basically made it sections of power parts, which will lead to faster replacement and also you don’t need so much training to replace these as they are basically big chunks or sections you slide out and replace.
In addition, since the inverter consists of four individual modules, it is possible to replace actually a complete quarter of the inverter. Basically, you could have for larger sites a whole complete module as a spare, and you could actually replace that in half a day, as compared to the old inverter, where you had to send a field team out, first investigate what the issue is, then order parts and potentially have to replace the whole skid. That could take about a week of time, so it’s vastly improved with this new modular approach.
This podcast is sponsored by Sungrow