Modeling DC Optimizers with Multiple MPPT Feature

I would like to model the following residential system that uses a string inverter with DC Optimizers:

Modules: QCells Q.Peak BLK-G4.1 295 (295W Monocrystalline 60 cell module)
Inverter: SolarEdge SE5000H HD Wave Inverter (so could use SE5000H-US [240V] 240V [CEC 2018] in SAM
DC Optimizer: SolarEdge P350 Optimizer

The configuration is:

Array 1: Tilt 20, Azimuth 180 - 16 modules on string all with P350 Optimizer
Array 2: Tilt 30, Azimuth 270 - 6 modules on string all with P350 Optimizer

What is the best way to model this with the upcoming Multiple MPPT modeling features in SAM?

Dear Michael,

For this configuration Array 1 and Array 2 will operate at different voltages because they have different string lengths and orientations. Is each string of modules/optimizers connected to a separate inverter input, or is there another optimizer or other device between the strings and the inverter?

Best regards,
Paul.

Hi Michael,

In this scenario, you would model the inverter with a single MPPT input, and account for electrical losses from the DC optimizers using the "DC power optimizer loss" option on the Losses page. You would also set the "module mismatch loss" on the Losses input page to zero.

There are some notes and instructions for modeling systems with microinverters in the SAM Help system, at the bottom of the Detailed Photovoltaic Model, Inverter input page's topic.

Best regards,
Paul.

Paul,

I've got a similar model setup for my home, two strings each at different azimuths and tilts and lengths. I'm using SAM 2018.11.11 r4 and I created a "Photovoltaic (detailed)" model that has a SolarEdge SE7600-H inverter and LG365 panels. On the "System Design" page I've got "SubArray 1" with 13 modules and "Subarray 2" with 9 modules and I get the following "warnings" in the large text box of "Electrical Sizing Information":

Subarray 1 string voltage exceeds the inverter maximum rated voltage at reference conditions. Consider using fewer modules per string.
Subarray 2 string voltage is below the inverter minimum MPPT voltage at reference conditions. Consider using more modules per string.

 It is was my understanding that a string with one DC optimizer per module provides a constant voltage to the inverter, see this  SolarEdge document . Thus I wouldn't expect a warning, although I don't see anyway to tell SAM I'm using optimizers other than in the "Default DC Losses" section on the "Losses" page. I'm very much a neophyte in all of this, so I assume I'm totaly wrong and would appreciate you setting me straight with a short explanation or links to information on the web.

Thanks,

Wink

Hi Wink,

Thank you for sharing the link to the SolarEdge application note for their DC optimizers and fixed-voltage inverters.
SAM does not explicitly model the DC optimizer, and does not model fixed-voltage inverters.

Those warnings are based on the design specifications of the array and inverter -- you can ignore them if you are confident your design will work given the manufacturer specifications.

SAM assumes that each subarray operates at its maximum power point. If the voltage at that point is higher than the inverter maximum MPPT rating, it sets the inverter input voltage to the maximum MPPT rating. A power optimizer would move the subarray operating voltage along the modules' power curve to adjust the power output of the array, but SAM doesn't do that.

In the attached dc-optimizer-fixed-inverter-voltage-tests.sam file, I demonstrate a technique you can use to remove inverter clipping: It involves using the Inverter Datasheet option to create a copy of the inverter with modified MPPT voltage limits so that SAM never clips the operating voltage. The "CEC Inverter Specs" case uses the inverter parameters from the CEC database: See my notes on the Inverter page and on the Losses and Data Tables tabs on the Results page. The "Custom Inverter Specs" case uses modified MPPT limits to avoid clipping: See my notes on the Inverter page.

Thanks,
Paul.

Txs for the info, a few questions:

On the "Inverter -> Inverter Datasheet" page it looks like the contents are not the contents of the selected inverter from "Inverter ->  Inverter CEC Database:"? This means I can't use that to "copy". I did find the "SE7600-H" information in "./libraries/CED Inverter.csv", but that information doesn't match up with what "Load data in file..." in "Inverter -> Inverter Datasheet".

I say this because when I "Save data to file..." from "Inverter -> Inverter Datasheet" I get the following:
When I try to match up that with the information from "./libraries/CEC Inverter.csv" using the third line ("variable names") of that file to interpret the datacontents and I get the following:

These 6 from "Saved data to file..." don't have a match in "./libraries/CEC Inverter.csv": Here are the "variable names" from the third line matched with the "Saved data to file..." info. The empty right side have no match: It seems modifing the "./libraries/CEC Inverter.csv" file might work, but even that doesn't provide all the information we see on the "Inverter -> Inverter CEC Database" page. In particular the "Efficiency Curve and Characteristics" has "Number o fMPPT inputs", "CEC weighted efficiency" and "European weighted efficency" but they aren't in "./libraries/CEC Inverter.csv". Nor do I see the "Inverter Temperature Derate Curves" information.

Neither technique seem to have "all" of the information, so  I'm not sure what to do, help appreciated.

-- Wink