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sharp spikes and dips in growatt inverter power output - how to troubleshoot?

deetoy

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Mar 15, 2021
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new install in Brisbane. 10kW growatt inverter with 10.3kW of panels.
single phase gride connection, 5kW feed in capped.
3 solar panel circuits on North, East and West facing roof sections at 9 degree pitch. (yes it's not ideal but work with what we have)

I'm seeing large spikes in power produced dropping from 5kW to 1kW several times per hour.
I have't found any faults in the growatt log.
house electrical loads are the usual domestic appliances, no pool pump or AC system. Only fridges, laptops, electric kitchen cooking appliances, led lightbulbs through the house.
off peak hot water system might be turning on and off. will try a period with it turned off.
I suspect there is some issue with the export limiter causing the inverter to turn off one or more of the three solar panel circuits when 5kW export limit is tripped.

I'm checking with the installer what cable size is used between the meter box and inverter.
the inverter has less than 500mm of cable run from meter box. basically next to the meter box.
I've read elsewhere, inverters will trip out when the sense excess voltage level from the grid. I can't see a voltage record in the growatt logs, will try to setup some datalogging to record voltage levels.

Suggestions on troubleshooting methods welcome.
also: yes I know 10kW system on a 5kW single feed in connection seems silly. preparing house for future electric car, batteries and using oversized solar system to cover more of my early morning, late afternoon power usage.
 

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Of what you described on the load side, ONLY the water heater could cause this. Which is not to say it couldn’t also be your other theory. I dont know anything about how inverters handle an ‘export limit’, so maybe this’ll be educational.
 
PV will cut back if there is no place to put the power. For example, if batteries are fully charged, or limited to max charge rate less than PV power, and you have variable AC loads, the PV power will jump up and down as needed to supply the variable AC loads.

This assumes you don't have an inverter capable of exporting to grid, which would give the PV an option to dump excess power to grid.

I assumes this is LF Growatt inverter. Believe it is limited to less than 3.5 kW per each of the two MPPT PV inputs or less depending on whatever the MPPT controller can handle for PV max current, which spec does not say. It might just temporarily shutdown the MPPT controller when it gets too hot from too much input.
 
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PV will cut back if there is no place to put the power. For example, if batteries are fully charged, or limited to max charge rate less than PV power, and you have variable AC loads, the PV power will jump up and down as needed to supply the variable AC loads.

This assumes you don't have an inverter capable of exporting to grid, which would give the PV an option to dump excess power to grid.
he is exporting.
 
I'm seeing large spikes in power produced dropping from 5kW to 1kW several times per hour.
Brisbane on 27 Aug was cloudy - the outputs for other PV systems as shown on PVOutput all show large variations in output through the day.

Here's a list of other solar PV systems in the postcode region 4000-4020 with outputs showing from yesterday:

Just choosing one at random which is a 10 kW system:

Screen Shot 2022-08-28 at 10.59.10 am.png

And another:
Screen Shot 2022-08-28 at 11.03.36 am.png

Looks to be a similar production pattern as yours (with different export limit perhaps).

It was just a day with lots of passing clouds. That's what clouds do to PV output.

Wait for a nice clear day. If you see large drops in output when it's actually consistently sunny, then you may have grid over-voltage issues.

But what you are seeing is what everyone else in Brisbane experienced.
 
thanks for the input. now I've had the system longer I'm gaining better understanding of the fluctuations in power output while the variation in solar radiation levels might not be so obvious to human eyes.
I have an emporia power monitor system tracking power useage on various circuits and gaining a better understanding of my power usage within my house.
 
new install in Brisbane. 10kW growatt inverter with 10.3kW of panels.
single phase gride connection, 5kW feed in capped.
3 solar panel circuits on North, East and West facing roof sections at 9 degree pitch. (yes it's not ideal but work with what we have)

I'm seeing large spikes in power produced dropping from 5kW to 1kW several times per hour.
I have't found any faults in the growatt log.
house electrical loads are the usual domestic appliances, no pool pump or AC system. Only fridges, laptops, electric kitchen cooking appliances, led lightbulbs through the house.
off peak hot water system might be turning on and off. will try a period with it turned off.
I suspect there is some issue with the export limiter causing the inverter to turn off one or more of the three solar panel circuits when 5kW export limit is tripped.

I'm checking with the installer what cable size is used between the meter box and inverter.
the inverter has less than 500mm of cable run from meter box. basically next to the meter box.
I've read elsewhere, inverters will trip out when the sense excess voltage level from the grid. I can't see a voltage record in the growatt logs, will try to setup some datalogging to record voltage levels.

Suggestions on troubleshooting methods welcome.
also: yes I know 10kW system on a 5kW single feed in connection seems silly. preparing house for future electric car, batteries and using oversized solar system to cover more of my early morning, late afternoon power usage.
Mine is doing this too with no load (nothing on AC circuits). I’m wondering if you found what this is?
 

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