PV output drops during peak sun hours

[CathM]

Hello from southern Spain. Total solar newbie here so apologies in advance for the non technical language and/or dim questions!
About 4 weeks ago we had 12 X 455 watts panels installed on our (flat) roof as two strings of 6 panels, with a Huawei Sun2000 6ktl inverter, grid tied to inject excess into the mains. First few days of operation with fully sunny days the PV output curve on the monitoring app was a beautiful bell shaped curve. Then we had a couple of weeks of cloudy days with very varied output but since then the production on a completely sunny day has been really strange - during the middle part of the day which would correspond to peak PV output, it completely drops away unless we are using something like a tumble dryer or other power hungry appliance. I will try to post screenshots to illustrate this. We have noticed that the mains voltage during these hours can rise to around 252v, when the "normal" value is 230v here, and we have had the supply to the house trip out a few times. From reading, it seems these voltage rises may be causing the drop in production as safety mechanisms kick in, and I have contacted the power company to look at the TAP setting on the transformer which supplies the house.
Meanwhile I was wondering if anyone here has any thoughts or suggestions on inverter settings which might help manage the problem? I understand the inverter has a voltage rise suppression menu but our installer does not seem to know much about it. Are there any other factors which might cause this sort of effect? Wiring issues? Dickery connections? I should add there are no shading issues during this part of the day.
Thanks you in advance for any help.

[jflorey2]

We have noticed that the mains voltage during these hours can rise to around 252v, when the "normal" value is 230v here, and we have had the supply to the house trip out a few times.

This is likely the issue. Generation rises, voltage rises, the inverter cuts out, the voltage drops, repeat.

This is reinforced by the seeming correlation between high loads and solar working. Loads drop the voltage and the inverter keeps working.

[CathM]

Thanks for the reply. It's helpful to know that we are thinking along the right lines - it seems solar power is so much more complex at times than panels plus sun equals lots of electricity!! I will update here if and when I get any joy with the power company. It may take a while and some determined effort - the power distribution companies here are notorious for being disinterested in helping resolve any solar related issues.

[oregon_phil]

Huawei has a forum. I searched the Huawei forum and found a forum thread under the title "Grid Parameter Settings for Sun2000 KTL" that pointed towards the following thread that says you need to be a special user.

You can search for this thread in google using the search terms:

en/doc/EDOC1100141536/6ffb0165/operations-related-to-the-special-user#EN-US_TOPIC_0226799007

[CathM]

Brilliant, thanks for pointing me in the right direction. I will get back to the installer with this. I believe he has access to these settings

[bcroe]

High line voltage tripping inverter monitors appears to be the
problem. I did 3 things to solve that here, ask the PoCo to
lower the voltage, reduce the voltage build up in the resistance
of my own wires, and raise the trip point of the monitors.
good luck, Bruce Roe

[CathM]

Thanks for the reply. I am getting really useful information here. In the event of the power company being uncooperative, do you think a domestic voltage optimiser would help, or would the inverter still not be able to function to export electricity if the mains voltage outside the property remained high?

[bcroe]

Good luck with the PoCo, your best chance. Here there was a 600 ft
loop connecting inverter to PoCo, I was able to reduce 9V build up in
the wire to only 2V using much bigger wire. In general I have used
over sized wire to carry solar generated power, to minimize losses.
If your loop is much shorter than mine, there may not be much room
for improvement. Worth checking.

Anything between the inverter and the PoCo must be able to handle
the full inverter power, and present a low enough impedance that the
inverter accepts it as a direct line connection.

Adjusting the inverter voltage monitors is very effective if you can do it.
Bruce Roe

[CathM]

That's great thanks. It's good to have more to go at. I will update with the response of the power company.

[jflorey2]

do you think a domestic voltage optimiser would help

Yes. Specifically an autotransformer to drop the voltage will help. However they are generally large and expensive.

[CathM]

Thanks for the reply. Definitely worth looking into, although maybe not financially practical then.