Effect of Power Factor on E_Grid (MWh)

[yazanabawi]

Hi All,

I am working with an inverter that has a rated ouput of 60kVA, and power factor range of 0.8 leading to 0.8 lagging.

In reality, the inverter will be at a power factor lower than unity, let's say 0.85, and I am trying to see this effect on the total energy injected to the grid E_Grid (kWh).

Since the inverter's output is 60kVA, at 0.85PF the real power output should be 60 * 0.85 = 51kW.

I have inserted the PF value in the miscellaneous power factor menu (cos phi) , but I do not see any considereble reduction in the E_Grid value, only an added EAPGrid.

I have also changed the inverter's parameter (Nominal AC power defined as: Apparent Power (kVA).

Has anyone tried this simulation before? any ideas?

Thank you very much.

[André Mermoud]

By introducing a Power factor, you have changed the PNom value at which the inverter will clip in case of overload.

Now this only affects the operating conditions when the Power will overcome the PNom value.

In other words you have diminished the PNom effective value from 60 kW to 51 kW (real power).

The effective loss will only intervene when your system will overcome this value (51 kW instead of 60 kW).

The overload losses are not proportionnal to the overload value.

The addifitonal loss will be strongly related to your over-sizing of the PV array: if you don't have any overload, there will be no effect at all.

[MarcoMalagnino]

Dear Mermoud,

according to your answer, the effect of a constant power factor on the PR of the system is only due to a possible rise of the clipping losses, thus having an effect only over the maximum nominal active power (in KW) delivered by the inverter. It means that during the time when the produced active power (AC side) is less then the Pnom of the inverter (adjusted according the given power factor) I will not get any energy losses.

In a way, the AC active power at the inverter output will be like the product of the dc power (inverter input) per the inverter efficiency (if no clipping or voltage limitation occur) until the current apparent power is less than the maximum apparent power of the inverter, right?

But in which way the inverter can produce an apparent power higher than the product of the dc power per the inverter efficiency?

Where does the rest of the apparent power (the reactive power) come from? From the grid? Or from the inverter?

Because as EPC company we have to give guarantee for the designed PR, I would like to be sure that I am not underestimating the effect due to the power factor.

I am not really expert of what the inverter in the reality does, but my understanding was different from what PVsyst simulates: I thought that the inverter produces an apparent power (kVA) equal to the product of the DC input power per inverter efficiency; if the PF = 1, then the active power (kW) would be like to the apparent power and there would be no additional losses, but if the PF < 1, then the active power would be like the product of the apparent power per the cos(phi), and it would mean that PR would be lower (proportional to the PF).

In my case for a project in USA we have to set the inverter with cos(phi) = 0,95 fixed.

According to my design (DC/AC ratio), as effect of a fixed cos(phi) = 0,95 PVsyst simulates additional losses of about 0,3% but actually I am not sure if these losses should be 5%?

Could you please clear this point, and if you have some references/articles about this theme, could you please be so kind to send them to me?

Thanks in advance,

Marco

[MarcoMalagnino]

Dear Mermoud,

I have asked to several different inverter manufacturers and all of them have answered that there will be an active power reduction due to a PF less than 1, only in case of overload (in a way, the PF<1 reduces only the overload limit of the inverter).

This is due to the fact that the reactive power comes from the Grid.

Best regards

Marco

[Mplo]

Marco,

I have the same question than you about the reactive power.

Thanks,

Miriam

[André Mermoud]

I have asked to several different inverter manufacturers and all of them have answered that there will be an active power reduction due to a PF less than 1, only in case of overload

This is exactly what I said in my first answer to this post.

The active energy production will not be affected, until the Pnom limit (in kVA) will be reached. The power factor acts as a diminution of the nominal output power (Pnom) expressed in terms of active energy [kW].

In your example: Pnom (apparent) = 60 kVA => with 85% PF Pnom (active) = 51 [kW] will be applied for limiting E_Grid when running the symulation.

PVsyst works in this way of course.

[dtarin]

I have asked to several different inverter manufacturers and all of them have answered that there will be an active power reduction due to a PF less than 1, only in case of overload

This is exactly what I said in my first answer to this post.

The active energy production will not be affected, until the Pnom limit (in kVA) will be reached. The power factor acts as a diminution of the nominal output power (Pnom) expressed in terms of active energy [kW].

In your example: Pnom (apparent) = 60 kVA => with 85% PF Pnom (active) = 51 [kW] will be applied for limiting E_Grid when running the symulation.

PVsyst works in this way of course.

 

Andre,

Will PVsyst work in the same way with inverters which have a temperature de-rate curve established in the OND file, such that the entire de-rate curve is multiplied by PF?

[LulaNord]

Hi...i am a new user here. As per my knowledge this only affects the operating conditions when the Power will overcome the PNom value.In other words you have diminished the PNom effective value from 60 kW to 51 kW .The effective loss will only intervene when your system will overcome this value. Edited June 23, 2017 by LulaNord

[André Mermoud]

Yes, the principle is the same for PNom values different due to the temperature.