Power Factor and Grid Power Limitation

[hvf]

Hello, everyone!

I am working on a project with 30x 185kVA inverters (5.55MVA total).

I am running two scenarios: 

1. Power Factor of 1, Grid Limit: 4,995kW
2. Power Factor of 0.90, Not Grid Limit

As you can see, both scenarios have an Active Power Capacity of 4,995kW and I was expecting to see the same energy produced. However, I am getting different values.

Could someone explain where is my reasoning wrong or add some clarity to what is happening?

Thank you for your time.

Best,

Hector

P.S.: I am using PVsyst 7.4, Trial Version.

Edited January 19 by hvf

[Linda Thoren]

Dear hvf,

The grid limitation is reflects a scenario where the grid manager impose a limit to the injected power to the grid. If your system at certain moment produce higher then this limit, it will be managed by the inverter as a clipping loss. There is a help page here explaining this further:
https://www.pvsyst.com/help/grid_power_limitation.htm

The power factor is the ratio between active and apparent power, i.e. Cos(phi) and does not limit the power to the grid at a certain threshold.  The active power is the power obtained along one sinus period, when we integrate the product of the instantaneous Voltage by the Instantaneous Current at each time step. This results in a multiplication by the cosine of the phase shift:

     Pactive  =  Ueff * Ieff  *  Cos(phi)   expressed in [kW].

The reactive power is the vectorial difference  of these contributions:

     Preactive  =  Ueff * Ieff  * Sin(phi)   expressed in [kVAr].

Following help page explain the Power factor further:
https://www.pvsyst.com/help/power_factor.htm

Indeed, if the Nominal AC Power is defined in Apparent power in the inverter file, the two variants should give similar results. To assist you further please provide us with the loss diagrams for the two variants, or send your project to support@pvsyst.com

Kind regards

[mohaned]

Similarly, i am seeing similar issue. 

I tried to run the simulation once with and without power factor. which gave a difference in output power.

However, i am not seeing added clipping losses.

Where is the extra loss coming from? and how to justify just loss?

 

[André Mermoud]

This is quite normal, and fully explained in the help “Project design > Grid-connected system definition > Power Factor”.

Your inverter PNom is very probably specified in terms of Apparent power [kVA]. In the “output parameters” page you should have:

Therefore if you are operating with CosPhi = 1, the PNom will be  2155 kW, but if you operate with a power factor of 0.95, the power limit will be Pnom = 2155 kVA, corresponding to an active power = 1048 kW.

This doesn’t represent an explicit loss, therefore this doesn’t appear on the loss diagram.
However you will se a difference in the overload losses.