Max Voltage restriction

[tecnun]

Dear Team,

I ve always had to "cheat" module and inverter maximum voltage due to open circuit string exceeding in unreal conditions, in order to avoid stopping simulation. In my opinion Voc (-10ºC) is an unreal restriction, as cell temperature is a lot higher in reference to ambient temperature. It implied a Polar temperature!. As we know voltage drops it temperature raise. Only this gap is small when there is no much radiation (and therefore voltage drops for other reasons)

Would it be possible to correct this bug?

Best Regards Tecnun

[André Mermoud]

This limit is a safety condition for the inverter and system.

The principles of the condition is explained in the FAQ "How to adjust the design temperatures ?"

This is not an invention of PVsyst, it is mentioned in the IEC norms.

Now you can adjust the Tmin value (minimum temperature ever measured at this site) in the project's parameters (button "Project's settings")

[tecnun]

André, i m attaching smth could be interesting for you guys. Please everyone consider it confidential as it took me time to make it. In my opinion sometimes IEC and other Norms should be updated (or refined).

As you can see (sorry that it is in spanish if you want i can translate this excel), i m supposing 0ºC (ambient temperature) and maximum radiation (close to 1000 W/m2) which in Mid-Chile could be rare as it happens at solar midday. And the worse case: The Plant stops and resumes at midday (in these events we consider Open Circuit not mppt). At any time Voltage exceeds 1000 V. Taking into account -10ºC of cells in PVsyst there is noway we can select a 1000 V inverter.

Would it be complex in PVsyst to develop SKOPLAKI formules? Good to be able to change Temperature (i didnt know it was possible), but as you can see in my excel, wind speed, height of anemometer at measures, rugosity of terrain, voltage drop upstream of the inverter are also present.

Best Regards Tecnun

Justificación Tensiones máximas SKOPLAKI_2.rar

[tecnun]

Hello again,

I ve just changed minimum temperature to consider at Open Circuit for max tolerable voltage at inverter: From -10ºC to 11,5ºC (which it is more realistic at 1000 W/m2 for our normal sites) but it keeps calculating at -10ºC, yes you can change it in hidden parameters but no effects in simulation. Am i doing anything wrong?

BR Tecnun

[tecnun]

Hello again,

I ve just changed minimum temperature to consider at Open Circuit for max tolerable voltage at inverter: From -10ºC to 11,5ºC (which it is more realistic at 1000 W/m2 for our normal sites) but it keeps calculating at -10ºC, yes you can change it in hidden parameters but no effects in simulation. Am i doing anything wrong?

BR Tecnun

 

It was solved in the past 6.7.5. Thanks a lot!!

[tecnun]

André, i m attaching smth could be interesting for you guys. Please everyone consider it confidential as it took me time to make it. In my opinion sometimes IEC and other Norms should be updated (or refined).

As you can see (sorry that it is in spanish if you want i can translate this excel), i m supposing 0ºC (ambient temperature) and maximum radiation (close to 1000 W/m2) which in Mid-Chile could be rare as it happens at solar midday. And the worse case: The Plant stops and resumes at midday (in these events we consider Open Circuit not mppt). At any time Voltage exceeds 1000 V. Taking into account -10ºC of cells in PVsyst there is noway we can select a 1000 V inverter.

Would it be complex in PVsyst to develop SKOPLAKI formules? Good to be able to change Temperature (i didnt know it was possible), but as you can see in my excel, wind speed, height of anemometer at measures, rugosity of terrain, voltage drop upstream of the inverter are also present.

Best Regards Tecnun

 

Was it useful?

BR Jose M

[Fdez. de Arevalo]

Hello team,

I´m using PVsyst 6.75 and I tried to change the minimum temperature for open circuit voltage of array from -10°C to -18°C what is more realistic in northeuropean countries but it remains Voc(-10°C).

I tried to do it in Preferences/Edit hidden parameters/Category:system design parameters/Minimum temperature for Inverter VAbsMax design. Then I checked it in the desing of the array und it didn´t change niether the minimum temperature nor the limitation of Voc.

I think I have done it right. Has anyone else this problem or am I doing sth wrong?

Few years ago I could do it but not with this version.

Thank you for your help.

Best regards,

Luis

[André Mermoud]

This information is now part of the project: in the project's definition dialog, button "Project's settings".

The value in the hidden parameters is just an initialization for new projects.

[tecnun]

Thanks André i didnt spot this useful new tool,

Fdez de Arevalo, are you sure you want to set -18ºC? Dont you think is too low? Take into account that that temperature is set in Standard Conditions and i am supposing that in midday and 1000 w/m2 the CELL (not ambient) temperature must rise

Of course i dont know how cold your site is haha!! just for you to check it out...

BR

Jose

[Fdez. de Arevalo]

Hi Jose,

I understand that -18°C is too low as min. temp. considering that in this situation the panels are producing the nominal power. It is the absolut minimum Temperature in a hourly TMY in northern Europe. We cannot set the same minimum temperature everywhere. About this topic I have only seen this paper "Dimensionado del nº máximo de módulos en serie según criterio de tensión máxima" and there is no database for this value for every location.

Has anyone a criteria for this minimum Temperature which shouldn't be the absolute minimum Temperature? A percentage? We cannot make a whole study as in Paper for every location. For being conservative and for having an argumentation I should use the absolute minimum temperature if I don't have a more accurate criteria.

Looking forward to having new ideas!

BR Luis