Inverter power limit

[Gerportela]

We are performing a simulation with an inverter brand XXX at a site in Spain. During the analysis, we observed differences between the simulation data and the DC current values defined in the OND file.

 

- In the Main Parameters window the inverter has a rated AC power of 4504 kW, with a maximum DC current of 5002.6 A, for a voltage U_DC of 915V. According to the manufacturer's data sheet these values correspond to operating conditions at 40 °C. (See Figure 1)

Figure 1

- In the Energy Managment tab, the "external ambient temperature (outdoor installation)" option is selected. See Figure 2.

                                                                                                                                                 Figure 2

 

- In the simulation, the site shows maximum ambient temperatures of 43 °C, without reaching 50 °C.

- However, when plotting the simulated DC input current and voltage points (extracted from the Uarray , IArray variables), it is observed that the maximum current values never exceed values expected for temperatures below 50 °C curve profile, not even close to the 40 °C profile (which would be the expected behavior).

Next figure (Figure 3) shows inverter input curves (V,I) for different temperatures and in yellow (Uarray, Iarray) points from simulation.

Figure 3

🔧 Additional details:

- Tests have also been performed by manually modifying the temperature derating profiles, even at extreme conditions, but the DC current results in the simulation do not change.

May be PVsyst is using the 50 °C inverter curve by default to limit the inrush current, regardless of the actual site temperature. Below we copy part of the OND file where the inverter operating limits are defined.

Converter=TConverter

    PNomConv=4504.000

    PMaxOUT=4504.000

    VOutConv=660.0

    VMppMin=915

    VMPPMax=1300

    Vmpp_PMax=915.0

    VAbsMax=1500

    PSeuil=20005.00

    EfficMax=97.00

    EfficEuro=95.00

    FResNorm=3.00

    ModeOper=MPPT

    CompPMax=Lim

    CompVMax=Lim

    MonoTri=Tri

    ModeAffEnum=Efficf_PIn

    UnitAffEnum=kW

    IDCMax=0.000

    INomAC=3500.000

    IMaxAC=3940.000

    TPNom=40.0

    TPMax=25.0

    TPLim1=55.0

    TPLimAbs=60.0

    PLim1=4001.000

    PLimAbs=2001.000

    PInEffMax =1800.000

    PThreshEff=49.90

    HasdefaultPThresh=False

 

❓Question:

- Is there any reason why PVsyst limits the input DC current according to the 50 °C profile even when the maximum ambient temperature conditions of 43 °C?

- Is it possible that PVsyst is using an estimated inverter internal temperature different from the ambient temperature to apply the curves?

- Why the simulation results do not show values with data at 40 degrees of the inverter?

Attached is also the comparative graph between the inverter input curves (by temperature) and the simulated values.

We thank you in advance for your attention and any clarification you can provide, we remain attentive for any additional information you may require.