On sunny days, Inverter switches off when DC voltage gets too high

[BOF GOM]

In December 2022 a local solar company fitted 23 Trina Vertex S390W panels in two strings. 10 of the 23 panels have optimisers fitted. They connected these to a Solis 6KW (rhi-6k-48es-5g) Hybrid Inverter and two Puredrive 5KW batteries. The system is connected to the grid as a producer and consumer of grid electricity.

Now that sunny weather is here, on very sunny days, between 1100 and 1200 local time, the inverter will switch off for a few minutes recording a “DC input overcurrent fault”. I can see from the graphs available that this occurs when the batteries move from 99% to 100% and the inverter DC voltage spikes from 2x 330v (=720v) to 2 x 387v (=774v). At other times of the day, when the battery reaches 100%, the DC voltage is not as high and the inverter does not switch off. Amps do not rise above 10.3A on each string, at any time.

The technical info for this inverter is:
Input DC (PV side)
Recommended max PV power 8000w
Max input voltage 600v
Rated voltage 330v
MPPT voltage range 90-520v
Full load MPPT voltage range 280-520v
Max input currant 11A/11A
Max short circuit current 17.2A/17.2A

I sense that there is a safety issue here, which will increase as summer develops. Too many volts implies that some component might overheat and ignite or its electronics burn out or even the inverter fails, as it would not switch itself off if there were no safety issues. I have not contacted the supplier company as the two technical people they had, have all left after completing my installation, having fallen out with the company’s new sales-driven owner. I wonder if I have been sold too may panels or if there needs to be an extra bit of voltage-limiting kit between the input strings and the inverter?

I would welcome your advice as to what I can do to sort this problem out.

 

[stuboy]

I'm slightly unsure of your connection. Can you clarify, do you have one or two strings? If two equal strings then the voltages are dealt with totally separately internally so there is no doubling of voltage. Your inverter maybe running into thermal overload problems perhaps or you are getting current spikes from the optimisers maybe? Would be useful to put a current clamp on the inputs to check. I assume you are monitoring these values on the inverter itself and not the app?
Cheers
Stuart

 

[Powerguy]

In December 2022 a local solar company fitted 23 Trina Vertex S390W panels in two strings. 10 of the 23 panels have optimisers fitted. They connected these to a Solis 6KW (rhi-6k-48es-5g) Hybrid Inverter and two Puredrive 5KW batteries. The system is connected to the grid as a producer and consumer of grid electricity.

Now that sunny weather is here, on very sunny days, between 1100 and 1200 local time, the inverter will switch off for a few minutes recording a “DC input overcurrent fault”. I can see from the graphs available that this occurs when the batteries move from 99% to 100% and the inverter DC voltage spikes from 2x 330v (=720v) to 2 x 387v (=774v). At other times of the day, when the battery reaches 100%, the DC voltage is not as high and the inverter does not switch off. Amps do not rise above 10.3A on each string, at any time.

The technical info for this inverter is:
Input DC (PV side)
Recommended max PV power 8000w
Max input voltage 600v
Rated voltage 330v
MPPT voltage range 90-520v
Full load MPPT voltage range 280-520v
Max input currant 11A/11A
Max short circuit current 17.2A/17.2A

I sense that there is a safety issue here, which will increase as summer develops. Too many volts implies that some component might overheat and ignite or its electronics burn out or even the inverter fails, as it would not switch itself off if there were no safety issues. I have not contacted the supplier company as the two technical people they had, have all left after completing my installation, having fallen out with the company’s new sales-driven owner. I wonder if I have been sold too may panels or if there needs to be an extra bit of voltage-limiting kit between the input strings and the inverter?

I would welcome your advice as to what I can do to sort this problem out.

Hi there , I’m no expert but researched this a bit when I fitted a 16kw solar system up . VOC is what you need to look at on the inverter , voltage open circuit . my panels had a voc of 44.1v each , inverter was 450 voc so I split my strings so as not to got over this ,panels can do 5-10 percent more voltage than stated this was taken into account too. Your 23 panels at 390 w will if at full power make 8970w taking it over your 8000w limit but maybe your optimisers turn this down I haven’t much knowledge on optimisers hope this helps

 

[BOF GOM]

Hi again,

Solis have kindly stepped in and loaded new firmware which looks to have sorted this problem out. Thanks for all your contributions.

 

[stuboy]

thats a great result. Have they said what the firmware change log is?