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wongtop:
I still think that it is the high AC voltage that is causing your clipping, and then the inverter needs to clip one or other or both MPPs.
My understanding is the inverter has to operate at a higher voltage (up to +2%) above the grid voltage. So your theory would imply that the problem is with the grid supply voltage being too high? I'm typically seeing my grid supply around 240-242V, with 244-246V from the inverter. If it's clipping due to the 246V limit, does it make sense that this would be correlated with power outputs >5kW?
I should note that my house does have a three-phase supply. But the PV and battery system are all on one phase.
billgates:
Are you able to run a bunch of heavy usage appliances like aircon, fan heater, oven etc when plenty of sun is shining to eliminate that your 5kW max generation is not due to export limit set which is correct for single phase. Only time the generation will be over 5kW is if your house hold usage is over 5kW or your solar battery needs charging to dump the excess solar there. If your house consumption is negligible and your solar battiers are full, 5kW generation is correc due to single phase export limit.
Interesting... You really got me thinking, that might explain things. Weather is dismal today, but when the sun returns I'll experiment to check this. However, I am struggling to believe that in three weeks we've never achieved >6kW generation simply because we haven't consumed enough.
In the previous example where the MPP outputs appear to be clipping, if I overlay the power exported to grid it is well below 5kW at that time:
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billgates:That's what I'm thinking. It would be interesting to see your consumption level and total power (kW) overlaid on that last graph for 9/4/24. If there is significant consumption occurring it would be unusual if the total production remained at 5Kw, unless of course it is cloud constrained. Is the export being monitored beyond your primary meter board?
EgorNZ:
So I've noticed an inverse relationship between the power output from the two MPP's in my solar system. When total output approaches >5kW, one MPP peaks and it's as though something forces the other MPP to dip, like they're coordinating to limit the total output.
What would cause this?
Are you able to run a bunch of heavy usage appliances like aircon, fan heater, oven etc when plenty of sun is shining to eliminate that your 5kW max generation is not due to export limit set which is correct for single phase. Only time the generation will be over 5kW is if your house hold usage is over 5kW or your solar battery needs charging to dump the excess solar there. If your house consumption is negligible and your solar battiers are full, 5kW generation is correc due to single phase export limit.
Coincidentally I've taken a look at my data when inverter throttling is happening and it does seem to drop MMP1 rather than share the reduction between the arrays. MPP2 retains its bell curve. Screenshot of this:
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billgates:
In Solar Web go to Analysis and click on History go to Device and select your inverter and under channels
- Current DC Current MPPT1
- Current DC Current MPPT2
- Voltage DC MPP1
- Voltage DC MPP2
- Power MPP1
- Power MPP2
Take tick them and it should show you a graph. Take a screenshot of that graph. It will give us a way better idea of whats going on.
Here's the same day again with those channels:
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Jase2985:
@EgorNZ any updates?
Weather conditions have been up and down for the last week or so, but I keep going back to this chart for 9 April. The more I look at it the more convinced I am that @wongtop is right, the voltage is key.
It shows:
Guy from Harrisons came to take a look at the problem a few days ago. They're going to follow up with the electrical contractor who did the install to investigate further.
He agreed that the 246V limit theory is a possible explanation. There is an 11kVA transformer right by my front gate, so he suggested it's possible we're the "first" property on the circuit, and Vector may have cranked up the supply to deal with lower voltage further down the road. If that is the problem, we'll be at the mercy of Vector to resolve it.
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