Questions Regarding Inverter Clipping and Module Temperature Settings in PVsyst

[Alex.el-mor]

Dear PVsyst Support Team,

I am currently working on two ground-mounted PV sites, and I have encountered two different issues during the simulations:

1. Inverter clipping time – In one of the sites, the inverter reaches clipping quite early, around 11:30 AM.
   Is there any way within the simulation settings to define or adjust the specific time when inverter clipping occurs?

2. Module temperature limitation – In another site, the module temperature exceeds 45°C, which significantly reduces the system’s performance.
   Is it possible to set or limit the module’s maximum temperature within the simulation parameters?

Thank you in advance for your assistance.

[Michele Oliosi]

Hi, these two factors are directly related to the components in your system as well as the weather. 

Directly setting a clipping time or a maximum module temperature would be unrealistic, and is not possible in PVsyst.

Instead, you can consider changing the components such as changing inverter model or PV module, or also changing the system layout.

[Alex.el-mor]

Hi Michael,

First of all, thank you for your response.
Unfortunately, in both cases, the system has already been installed, and I don’t have the option to replace the equipment.
It might be worth considering adding this function in future versions.

[Michele Oliosi]

Glad to help !

I see, however I still fail to see the purpose of this request, sorry. If the inverter clips at a given time, this means that at that time the PV production reaches the clipping threshold at that time. If you model the PV production based on the measured data (not from a TMY), the clipping time should at least roughly correspond to the reality. 

Same thing with the module temperature, if you were to model using the real historical weather data, the temperature of the modules, measured and simulated, should at least roughly match.

Let us know if I missed something about your intentions with the simulation.

[Alex.el-mor]

Hello Michael,

I would like to clarify my question.
Does the simulation calculate the PR while taking into account the system’s location and the fact that the inverter experiences early clipping?
I’m asking because, according to the system monitoring data, I can see a difference in PR between the simulation results and the actual performance on site.

Another question — regarding the panel temperature:
Does the simulation consider the temperature variations of the panels? Since when the temperature rises, the panel’s output decreases, this factor also affects the system’s PR.
In addition, does the PR value shown in the report reflect the PR including temperature effects, or should a PR corrected value be presented in the report instead?

[Michele Oliosi]

The simulation models both the location and the temperature, provided you have parametrized these properly. If the inverter malfunctions, you could also derate the inverter in PVsyst.

Moreover, it is important to import the historical weather data corresponding to the monitoring period. Can you confirm whether you are using the corresponding time series for your simulation? 

If you are using a compatible time series as input for the simulation, it is then worth to compare the measured and simulated time series to understand whether the discrepancy correlates with any factor. Usually comparing the yearly PR and measured PR is not very telling per se.

I think you should use the standard PR. However, it depends on how you are calculating the PR for the measured performance data. You should match the definitions of simulated an measured PR.