Reactive and apparent energy values in the loss diagram

[julmou]

Hello,

I have been simulating the use of Power Factor on a 20MW solar farm. The inverters used are 20x SMA Sunny Central 1000CP XT. I have checked the inverter definition and it allows power factor specification, with nominal AC power being apparent power (kVA), in the output parameters.

Now, once I'm happy with the whole system, I used the Energy Management section, and specified to "Use Power factor for grid injection" with a tan (phi) = -0.484, and cos (phi) = 0.9, so a Leading power factor. So far so good.

Now, the results in the Simulation confuse me a bit. The active energy is all good (obviously more overload loss but it's okay). But I can't interpret well the two values at the bottom of the loss diagram , please see the attached screenshot. 

Quote

20.87 kVAR    Reactive energy from the grid: Aver. cos(phi) = 0.894

46.64 kVA     Apparent energy to the grid

First of all, is this energy or power?....  Either it's energy and then the units should be kVARh and kVAh, or it's power but then is this the average power over the whole year, the constant reactive power that's generated, or something else?

Second, if my system is leading (so "producing reactive power"), I don't understand why it says "Reactive energy from the grid".

I tried then to simulate with a Lagging power factor (tan (phi) = +0.484, and cos (phi) = 0.9), so if it's lagging (like a motor/inductance) it's "consuming" reactive energy from the grid. And this time, the simulation report indicates "Reactive energy to the grid". So I'm really confused...

[André Mermoud]

You are right, there is some confusion in the report here.

The result is indeed an energy, to be specified in  kVARh  and KVAh

And we will harmonize the denominations "From the grid" and "Towards grid.

[julmou]

Hi,

Thanks André :)

Regarding the "from grid" and "to grid", I was checking again, and maybe the mistake, or confusion is not in the report but in the settings.

When I enter cos (phi) = 0.9 and tan (phi) = 0.484, tan (phi) is positive, so the angle phi is positive, so we're in a case with a leading phase shift. However, the settings automatically indicates Lagging... So, unless we are meant to give the phi, tan(phi) and cos(phi) from the grid point of view (?) and that the Lagging or Leading is the one of the grid, then the mistake is here. And in that case, the report would be right in saying Reactive energy to the grid.

Inversely, with cos (phi) = 0.9 and tan (phi) = -0.484, I have a phi < 0, so a Lagging system, and the settings in PVsyst Energy Management indicates Leading. I think the confusion is there.

See snapshots below.

[allison.mueller]

Hi julmou, I have noticed this too. It may be tied in with a bug I just submitted, wherein no matter what is entered here, the report says the power factor is "lagging".