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Negative annual energy when switching from AC connected to DC connected PVS

  • browne0
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10 Dec 2021 17:16 #10376 by browne0
Negative annual energy when switching from AC connected to DC connected PVS was created by browne0
Model: PV-Battery, Single Owner
Size: 28 MW-dc, 17 MW-ac, iterating battery capacity to determine best fit

AC Connected with Manual Dispatch provides the expected increase in energy from the system.

Without changing any other inputs, switching to DC connected, automated dispatch, and perfect look ahead always delivers the following notice and has substantial negative annual energy: "Inverter oversized: The maximum inverter output was 13.34% of the rated value 16940 kWac". I'd like to only charge from the system and clipped system power and size the battery to optimize for that for now for a more simplistic case.
I'm running an external financial model and am not changing other default inputs from a NREL 2020 webinar download. The same outcome happens for a Merchant Plant SAM model. The reference file is attached.

Appreciate any thoughts.

File Attachment:

File Name: DCCoupledv...dPVS.sam
File Size:1,365 KB
Attachments:

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  • pgilman
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10 Dec 2021 19:13 #10378 by pgilman
Replied by pgilman on topic Negative annual energy when switching from AC connected to DC connected PVS
Hi Eric,

This is caused by a bug in SAM 2021.12.02: github.com/NREL/SAM/issues/856

Thank you for bringing it to our attention.

For now, please set the transformer losses on the Losses input page to zero. You can add the transformer loss to the AC wiring loss as a workaround until we fix this issue for the first update to SAM 2021.12.02, which we plan to release in January.

Best regards,
Paul.

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