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 Post subject: Grid power limitation
PostPosted: Tue Sep 23, 2014 7:23 pm 

Joined: Thu Aug 21, 2014 11:34 am
Posts: 18
Hello!

I applied a grid power limitation of 2.55 MW to a system. I output the hourly "available energy at inverter output" before and after applying the grid power limitation. I noted that all values greater than 2.55 MJ/hr were reduced to values below 2.55 MJ/hr, causing losses. Why are the values not reduced to exactly the clipping limit?

Many thanks,

Jenna


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PostPosted: Sat Sep 27, 2014 6:14 pm 
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Joined: Mon Apr 16, 2012 7:29 pm
Posts: 1616
In the present time the limitation is applied to the inverter output. Therefore all losses after the inverter are effective losses.

Now technically, this is probably a current option in the reality, at least for systems with a single inverter.
Clipping the power at the injection point would imply that the power effectively measured at the injection point level would be communicated to the inverter's electronic control for adjusting its exact operating point at each instant.
See the previous discussion Grid Power Limitation about this subject.


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PostPosted: Fri Oct 03, 2014 6:18 pm 

Joined: Thu Aug 21, 2014 11:34 am
Posts: 18
Dear André,

Thank you for your response and for directing me to the other thread.

Apologies if I've misunderstood, but I wasn't considering any losses after the inverter: rather than examining the output at the grid injection point, I was examining the output at the inverter, which is where the limitation is applied. So why are the clipped values of the inverter output, 'EOutInv', dipping below the threshold? For example, I'm imposing a clipping limit of 2.55MW, so I assume that an unclipped 'EOutInv' value of 2.61MW would be clipped to exactly 2.55MW, whereas it is actually clipped to 2.53MW.

I'd appreciate if you can help me to understand the process more :)

Best wishes,

Jen


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PostPosted: Sat Oct 11, 2014 11:00 pm 
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Joined: Mon Apr 16, 2012 7:29 pm
Posts: 1616
Which version of PVsyst are you using ?
I had corrected the little discrepancy (0.7%) - which was due to a calculation artefact - some months ago.


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PostPosted: Wed Oct 15, 2014 12:59 pm 

Joined: Thu Aug 21, 2014 11:34 am
Posts: 18
Hi André, I'm using version 6.25.


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PostPosted: Wed Oct 15, 2014 10:08 pm 
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Joined: Mon Apr 16, 2012 7:29 pm
Posts: 1616
I don't remember when I had done this correction (probably in an earlier version). Please try to update.
If this error persists, I don't have an explanation. Please send me your full project, using "Files" / "Export projects" in the main menu.
However such a discrepancy on only a very few of hours should not produce a big error.


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PostPosted: Wed Feb 07, 2018 10:32 pm 

Joined: Fri Jul 29, 2016 10:32 pm
Posts: 6
Hello,

I seem to be having a similar issue as described above using version 6.68. With no grid limitation, my project has many hours above 998KWac, as high as 1,045KWac. Setting a grid limitation at the inverter of 998KWac, instead of reaching this value the maximum hourly output at the inverter is now roughly 955KWac. Why would this be?

Also, I have tried switching between applying the limitation at the inverter and at the injection point and the simulation is no different despite AC ohmic and transformer losses. This also seems strange.

Thank you


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PostPosted: Fri Jul 05, 2019 8:08 pm 

Joined: Wed Jul 03, 2019 10:29 pm
Posts: 3
Location: Houston
I am using 6.81 version of PVSYST. My external transformer losses are coming very high especially resistive/inductive losses. My losses are coming out to be 1.09%not at STC which I think is high as in previous version of PVSYST we use to have a lesser value. I know it depends upon I square and current depends upon the irradiance therefore,my question is if PVSYST is considering irradiance from TYM3 weather data and changing the losses or is there a bug in the system?
Thanks for your help.


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