Module Voc temperature coefficient is not applied to Vmp

I'm modeling a system where the Vmp of the string is just slightly above the Min MPPT voltage of the inverter and I'm concerned about the effect of the Vmp's negative temperature coefficient causing the Vmp to drop below the inverter's spec at high temperatures. To confirm that SAM was correctly modeling this, I used the "CEC Performance Model with User Entered Specifications" and recreated the module from the library, but with an exaggerated value for Voc temperature coefficient. I expected, lacking any specific data about the Vmp temperature coefficient, that SAM would apply the Voc coefficient to Vmp, and there would therefore either be a warning or a severe loss of output power. In actuality, the Voc coefficient had very little effect on the output power, even when I set the Voc coefficient to +/- 1000V/C!

I would expect SAM to provide a warning, either on the System Design page or upon simulation, indicating that at the expected temperature extremes the array will exceed the inverter's MPPT limits.

Dear Bob,
Thank you for the suggestion. SAM does not generate a message when the array string voltage falls outside of the inverter MPPT minimum and maximum ratings. It's worth doing a quick check of the array voltage (Subarray 1 DC string voltage in the time series graph) to make sure it is within limits acceptable for your design.
SAM does generate a simulation message when the array string DC voltage exceeds the inverter's maximum input voltage rating (Vdcmax). However it does not limit the array voltage when it exceeds this rating, so you will not see a reduction in the system's output when that happens.
If you design the system so that the design specifications do not exceed nameplate ratings, you can generally assume that the system will operate within its limits. As a techno-economic model, we've designed SAM to strike a balance between complexity and usability, so it does not model a lot of the physical detail of a real system.
For example, SAM generated the message below when I simulated a system with an array that had too many modules per string (Vmp at design of 601.7 V, which exceeds the inverter maximum DC voltage of 600 V). If you click Continue, SAM displays the results with high array voltages even though you would not design a system to operate in this way.

Having said all of that, we do appreciate feedback like yours, and do have plans to add more detail to the photovoltaic model, and will take your suggestion into consideration.
Best regards,

Paul.

Hi again,
I forgot to mention the Inverter Sizing Information macro that gives you a report of the inverter's performance. To use it, after setting up the PV system, click Macro at the bottom left corner of the SAM window, and then click Inverter Sizing Information and Run (at the top of the window) to generate the report.
Best regards,

Paul.