Inverter Temperature Degrading

[Cleyson]

Hello folks, I have been reading some topics in the forum but I did not achieve to a final conclusion regarding the understanding of how PVSyst uses inverters temperature in the simulation.

1. In the OND file it is informed pretty much points combining Temperature and Power. The temperature informed is the Ambient Temperature or the Inverter's Temperature?

2. On Energy Management -> Inverter Temperature. There are 3 options:

a) Ambient temperature on exterior - Does it consider a perfect cooling of the inverter? Hence the inverter is always operation unders the ambient temperature? 

b) This one is pretty clear, adding a extra fixed temperature on top of the ambient temperature. OK

c) Pretty much ok too. The inverter temperature varies according to the PV power input. Is there any usual number that could be used for reference either for central and string inverters?

 

My final question is:

If the temperature informed on the OND file is related to the ambient temperature, how does PVSyst considered the heating deagrading on the inverter?

But if the temperature informed in the OND is the Inverter's temperature, how does PVSyst estimates the inverter's temperature?

 

Finally, for my real case scenario, a PV plant in Brazil in a hot location (28ºC to 40ºC). What is the proper way of running simulations that considers temperature degrading on the inverter?

 

[Linda Thoren]

Dear Cleyson,

Thank you for your question. In the simulation, the inverter derating will depend on the inverter temperature. By default, the inverter temperature is the same as the ambient temperature, but this behavior can be changed in the Energy management tab.

1.       In the OND file in the Output parameters, it is the Inverter's temperature that is indicated. With an increase of temperature, the Maximum Power is often limited. These values are defined by the manufacturer in the datasheet. In the case the temperature exceeds the threshold of where the power is limited this will be taken into account in the PVsyst simulation as an (extra) overload loss

2.       Energy management
a)       External ambient temperature thus assumes that the inverter has the same temperature as the outside. 
b)       External ambient temperature with shift allows to define that the inverter temperature will follow the ambient temperature, plus or minus a constant value in degrees that is defined as the "Temperature increase". For example if you define a temperature increase of 5°C, and at a given time the ambient temperature is 38°C, then at that time in the simulation the inverter temperature will be 43°C.
c)       Fixed temperature, correspond to the case the inverter is placed somewhere with a fixed ambient temperature (for instance inside with cooling) with a possibility to increase the temperature according (proportionally to) to the irradiance on your field, i.e. the power generated.

In the meteo file for your site, the ambient temperature and irradiance are available and according to your definitions in the energy management tab, the inverter's temperature is estimated. The simulation will consider the limiting effects on the inverter at high temperature according the the output parameters in the OND-file.