Modeling losses when Vmp is lower than the MPPT range

[Shwetha Vara]

 

• How does PVsyst account for losses when the temperature-adjusted Vmp of the panels falls outside the microinverter’s MPPT operating range? What is the typical impact on power production accuracy in such cases?

• Which inverter parameters in PVsyst can be adjusted to model the power reduction accurately when this condition occurs, ensuring the losses are properly represented?

 

[Michele Oliosi]

Hi, PVsyst will use the operating range to displace the operating point on the IV curve.
This displacement away from the MPP will cause losses, captured in the variables IL_..., e.g. IL_Vmax for the maximum voltage. The parameters here are the Vmax and Vmin parameters.

Note that a different yet related loss, the derate at very high or low voltage levels (or more generally as a function of voltage), is not captured by PVsyst. We do only model a voltage dependence by means of three caracteristic efficiency curves based on three ordinary voltage points. However this may not capture the full voltage derating curve.

[Shwetha Vara]

Thank you! One follow up -  is there an output curve or visualization to view the losses when the MPPT operating point is displaced? Trying to understand how that calculation works.

[Michele Oliosi]

You can set up the module layout tool in one of your projects for a sample visualization in a concrete case. The impact of inverter limits is displayed and is similar to the simulation so it will help understand.

Other than that there are some explanations in our help, for example:

https://www.pvsyst.com/help/physical-models-used/grid-inverter/inverter-operating-limits.html

However, there is no visual representation of what actually happens during a simulation. You could check the output variables IArray and UArray though. Together these represent the DC array's operating point.