question

Matt Knight avatar image
Matt Knight asked

Change MPPT Tracking Refresh Interval

We collect data from our Victron system and store it for analysis. Here you can see the power generation curve from our rooftop solar panels, connected to a Victron 100/50 solar charge controller.


As you can see, every 10 minutes, the power drops off dramatically. I'm guessing this is the solar charge controller sweeping to find the Maximum Power Point.

Each of these "sweeps" takes ~33 seconds to complete, and during this time, power production decreases dramatically - the middle drop on the chart above is ~158W to ~120W average or so (about a 25% decrease). Power production after the sweep appears almost completely unchanged - looking at the PV input voltage, it reduced by ~0.18V (from 34.50V to 34.32V).

Treating this as a duty cycle and averaging over time, a 25% drop for 33 seconds every 10 minutes corresponds to roughly a 1.4% total drop in output.

Questions:

  1. Am I understanding the purpose of these drops correctly?
  2. Would the MPPT adjustment provide >1.4% improvement to output during the next 10 minutes?
  3. Is it possible / does it make sense to make the interval between these event adjustable - i.e. a user setting to change it?

Thanks,

Matt

MPPT ControllersSolar Panel
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8 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

1. I can't say for sure, but that seems like a pretty reasonable explanation.

2. This is impossible to say either way. On clear, sunny day conditions, then the loss during the sweep will probably be larger than the gain in finding the new MPPT but that is usually when you need it the least. In variable weather conditions, the gain from finding the new MPPT will probably be larger than the cost of the sweep, and that is when you need it the most.

3. This is not currently possible for an end user to change. Sorry to say It is extremely unlikely that the firmware and software development time would be taken to make this into a user facing feature.


Now questions for you, how fast is your sample rate on that data? And what did you use to capture it?

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markus avatar image
markus answered ·

Hi @Matt Knight,

"happy to share what we have"

Yes. This sounds very interesting. It would be great, if you write an article in the new "mods space"

launching-the-mods-space-a-new-section-on-communit.html

I am sure it would be interesting to many, if you could give a little bit of advise how to set this up.

Best Regards,

Markus

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sean avatar image
sean answered ·

I find it somewhat implausible that the MPPT sweep frequency is once every 10 minutes, and that 33 seconds is the period of time required to recalculate the new maximum power point.

Surely this isnt correct ?

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markus avatar image
markus answered ·

It seems that this behavior is spotted by more and more people.

spotty-drops-in-solar-generation.html

I had a chance, to have a close view on my solar setup this weekend. I don't have those sweeps...

But I have to mention, my solar charger is pretty oversized for my installation and it is only utilized by half of its load capacity at maximum yield.

Best Regards,

Markus

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rainerb avatar image
rainerb answered ·

Hello,

I can also see these "spikes" with my MPPT100-50 (every 10 minutes) and I have a direct comparison to my Fronius Galvo AC inverter.

My two PV arrays are directly next to each other on the same roof and same direction.


In my opinion these mppt spikes really annoys the ESS regulation. The sudden loss of mppt pv power often switches the inverter from charging to discharging and a few seconds later it feeds battery power to the grid until the ESS regulation is up to date again.


MPPT100-50 with spikes


Fronius Galvo with a smooth production (same date and time)

Best regards

Rainer



mppt100-50.png (18.8 KiB)
froniusgalvo.png (15.4 KiB)
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custom avatar image
custom answered ·

Hello,

is there anything new on this issue?

I have also noticed the voltage drop every 10 minutes during a Bluebird day while my MPPT 75/10 is in bulk mode. I read the data directly from the VE.direct port.

Will this behaviour improved in future firmware versions?

Thanks!

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Fra avatar image
Fra answered ·

I am evaluating a controller with an almost flat efficiency curve at any power at 99%.


And a double mppt routine with 6,000 changes per second.


And a 30mhz processor.


I noticed that the victron smartsolar in boost-mppt seems to vary the voltage up and down a little faster than once per second.


also noticed that in case of partial shading of 33% of the panel longitudinally on purpose, the controller stays for 3 minutes on a false MPP losing 3/4 of power. (Negative fact).

screenshot-2022-10-13-11-47-32-289-comvictronenerg.jpgImage Caption

screenshot-2022-10-13-11-47-28-761-comvictronenerg.jpgImage Caption

Only after 3 minutes does it find the true mpp at about half voltage and recover all the power possible.


I also noticed a full swap of the voltage curve every 10 minutes lasting 10 seconds.

In my case last 10 second not 33 second.

screenshot-2022-08-30-10-16-30-134-comvictronenerg.jpgImage Caption

screenshot-2022-10-15-10-21-11-777-comvictronenerg.jpgImage Caption

screenshot-2022-10-15-10-21-04-314-comvictronenerg.jpgImage Caption

And I noticed that in case of sudden load increase from no-mppt phase to mppt phase the controller performs 4 complete swaps of the voltage curve (positive fact).

screenshot-2022-08-29-13-03-02-435-comvictronenerg.jpgImage Caption


Thank you


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gerard-van-seventer avatar image
gerard-van-seventer answered ·

Does anyone know a solution for this "issue"?

I'm having a SmartSolar Charger MPPT 250/70 (v1.59) with the same issue. Since energy is expensive and any watt counts I would expect a better mppt algorithm.

Here are my graphs with the issue.

mppt-dips-1.png

And some more detail

mppt-dips-2.png

--Gerard


mppt-dips-1.png (76.3 KiB)
mppt-dips-2.png (47.9 KiB)
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Related Resources

MPPT Product Page

MPPT Error codes

MPPT 150/60 up to 250/70 Manual

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