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Threshold loss when array power > inverter threshold


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I ran a simulation and noticed that there are certain hours where the inverter is flagged as offline and the power loss is assigned to the "IL_Pmin" category, which is supposed to be because array power is below the threshold of the inverter.

However in my case, for the hours that are lost due to inverter threshold, the input power is actually 5-6x the inverter threshold.

This is sort of a "double whammy", because not only are those lost production hours, but there is also nighttime inverter loss associated with these hours.

See the below example, in which an inverter with a 2500 W (2.5 kW) threshold is losing power.  For reference, just a single central inverter (2200 kW) is being used for this project.  Power units are in kW.




Can someone explain why this is happening?  The result is a lower yield than I would expect.

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In general, it looks as though PVsyst has a minimum built in, irrespective of what is stated in the OND file. EArrayMPP must be greater than 0.5% of Pnom, and I think there might also be an irradiance requirement, although I can't find the details at the moment. Changing the setting below did not change behavior in my test. Results were pretty consistent with the 0.5% requirement, but there were four hours where there was inverter output below this. 





Edited by dtarin
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  • 3 weeks later...

FYI I think this threshold loss is based on minimum current.  Several simulations that I've run show a threshold loss below a certain minimum IArray.  What that IArray is, however, remains a mystery.  Just frustrating that PVsyst's behavior is unexpected and doesn't follow its own documentation.

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