CE+T Stability 30C3 Multi-directional Power Converter DC Design & Grounding

[JimmysLimeade]

Hi, I am working on a DC side only design where they want to utilize the CE+T Stability 30C3. They are using 2 of those converters with 120 480W modules. My plan right now is to do 4 strings of 15 modules in series (totals to 804V) and then connect those in parallel (I dont really know the best way to do this so suggestions would be helpful) to hit 45A. Each converter has a maximum input of 1000V and 60A on the DC port which is why I decided to do it that way, but I need to know if I was correct in my reasoning here or if I need to fix it.

Another issue I am having is the grounding for this system. I am at a complete loss with this whole grounding document I attached below, it seems like none of the scenarios really fit what I need and I dont know how to properly adapt my system to be grounded correctly. Ive been looking into the negative ground referenced monopole option which would make the most sense to me, but I dont know how to best show that in my diagram.

I have been using a document from CE+T to base my initial design on but its somewhat lacking in detail of how to ground.
Sorry for all the questions, I just want to make sure I get everything here right.

 

[pv_n00b]

Hi, I am working on a DC side only design where they want to utilize the CE+T Stability 30C3. They are using 2 of those converters with 120 480W modules. My plan right now is to do 4 strings of 15 modules in series (totals to 804V) and then connect those in parallel (I dont really know the best way to do this so suggestions would be helpful) to hit 45A. Each converter has a maximum input of 1000V and 60A on the DC port which is why I decided to do it that way, but I need to know if I was correct in my reasoning here or if I need to fix it.

You will need a fused disconnecting DC combiner. Pretty common stuff there. This inverter also accepts a BESS input, are you incorporating a BESS into this? If not why use this particular inverter?

Another issue I am having is the grounding for this system. I am at a complete loss with this whole grounding document I attached below, it seems like none of the scenarios really fit what I need and I dont know how to properly adapt my system to be grounded correctly. Ive been looking into the negative ground referenced monopole option which would make the most sense to me, but I dont know how to best show that in my diagram.

This inverter is strange in that you can have a positive ground, negative ground, or ungrounded PV array, in addition to some bipolar setups that have not been used in a long time. Seems like a lot of extra cost to have these options when the typical is now ungrounded. I would use the ungrounded (floating) option just to match the rest of the industry. I have not looked at it since it's not standard to ground PV arrays anymore but the Tigo optimizers might not like grounded PV arrays. I assume you are not concerned with complying with rapid shutdown in this system.

 

[JimmysLimeade]

You will need a fused disconnecting DC combiner. Pretty common stuff there. This inverter also accepts a BESS input, are you incorporating a BESS into this? If not why use this particular inverter?

This inverter is strange in that you can have a positive ground, negative ground, or ungrounded PV array, in addition to some bipolar setups that have not been used in a long time. Seems like a lot of extra cost to have these options when the typical is now ungrounded. I would use the ungrounded (floating) option just to match the rest of the industry. I have not looked at it since it's not standard to ground PV arrays anymore but the Tigo optimizers might not like grounded PV arrays. I assume you are not concerned with complying with rapid shutdown in this system.

Thanks for the reply! I am adding a BESS to the system, I just didnt show it there, which was my bad. Ill use the ungrounded option and show a fused DC combiner here.

Thanks again!

 

[pv_n00b]

Thanks for the reply! I am adding a BESS to the system, I just didnt show it there, which was my bad. Ill use the ungrounded option and show a fused DC combiner here.

Thanks again!

In that case I would check the BESS documentation to see if it requires a grounded or ungrounded DC feeder to the inverter and put in whichever it requires. It's not clear from the inverter doc if the BESS and PV DC inputs can have different grounding, so be careful if you think you need to have different grounding on the PV and BESS.