# How to create a P-Q curve of the solar farm

Hi there

Right now, I am trying using PSSE GUI to create a P-Q curve for the solar farm. I already build the SMIB which is connect to transformer and the generator. However, what is the next step to get the data for create the P-Q curve(to confirm the Reactive Power Capability of the solar inverter) of the generator?

Does anyone know what is the reason?

Thanks very much for your valuable time and kind help in advance!!

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I don't understand what you want to do. Is it for load flow calculation or a dynamic simulation?

( 2019-08-26 03:31:44 -0500 )edit

I am not sure it is for load flow or a dynamic simulation. However, I think it may be load flow calculation. I just want to get the P-Q curve to confirm the reactive power capability of the solar inverter. Thank you very much.

( 2019-08-26 04:06:01 -0500 )edit

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To get the P-Q capability curve of a solar plant at its POI - In the load flow case, choose an operating mode for the solar plant (k-power factor, v-control...) and choose a voltage setting (typical value of operation or 1.0). Also choose a MW increment (maybe 10% of Pmax). It is important to have a line separating the POI bus of the solar plant from the SMIB generator. Then:

1- dispatch the solar plant at Pmin (say 10% of Pmax)
2- solve the load flow and record the P and Q output leaving the POI bus, point (Ppoi, Qpoi)
3- add the MW increment to the dispatch value of the solar plant (say now at 20%)
4- go to step 2 and repeat until the solar plant reaches its Pmax value


I would recommend to perform such study in a realistic network at the POI where the solar plant is located.

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Thank you very much. It is very useful. However, I still have a little issue. This method can only get + active power & + reactive power (half of the P-Q curve). How can I get - reactive power with + active power? Thank you very much.

( 2019-08-28 04:44:37 -0500 )edit

For the region "- reactive power with + active power", you drive the generator under test in its leading power factor by lowering its voltage settings (to 0.98 or less) until -Q is produced by the load flow.

( 2019-08-28 10:04:39 -0500 )edit

The P-Q capability curve for a solar inverter is typically provided by the solar inverter manufacturer. In some studies it is important to establish the P-Q capability of a solar farm (as measured at its point of connection), which has multiple inverters, transformers and cables etc. To get the solar farm P-Q curve, you must do successive power flow calculations, respecting the P-Q limits of the individual inverters in each calculation.

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Yes, what I really need is to create the P-Q curve of the solar farm. I already build a SMIB system with the generator(solar inverter) and also finish the power flow calculation. However, I still don't know how to get the P-Q curve of the solar farm... Thank you very much.

( 2019-08-27 04:04:09 -0500 )edit

I advise you to set up a Python script that will increase P in steps, and calculate Qmax and Qmin at each step value of P. You can write the results to a text file, CSV or Excel file, and do the plotting from there.

( 2019-08-28 08:21:49 -0500 )edit

Hi jfconroy, thank you very much. However, as I am a freshman for Python. Could you please help me how to set up? Thanks in advance.

( 2019-08-28 09:17:50 -0500 )edit

Learn Python. It is specifically designed to be easy to learn. Learning to write the code yourself is much more beneficial to you than getting code "off the shelf" from someone else. Besides, the point of this forum is not for some members to provide "off the shelf" Python scripts to other users.

( 2019-08-29 03:01:10 -0500 )edit