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jejochen avatar image
jejochen asked

ESS system: AC coupled PV backfeeds to grid instead of charging batteries when mppts charging

Hi,

I searched for this question, but didn't find any similar. If there is so, i apolegise for double posting.

I have an Ess system installed with 3 5 kVa multiplus 2 inverters on 3 phase. An AC coupled PV inverter metered by EM24 meter, grid is also monitored by an EM24 meter, and 2 250/85 mppt's installed. 85 kWh bank lifepo4 with batrium bms.

When the mppt's are on, the excess solar from the ac coupled array is injected into the net instead of used to charge the battery. This surpasses what the meaning of this system is, so is there a solution to get this energy to the battery?

ESS
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Murray van Graan avatar image Murray van Graan commented ·

Which PV inverter are you using?

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jejochen avatar image jejochen Murray van Graan commented ·

A diehl 3phase inverter. A brand that went bankrupt

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4 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi,

The first thing to check is that the AC PV is set to the correct location (either on the input or the output of the multi) in the PV Inverter menu on the GX device.

Once that is confirmed to be correct, check the DVCC charge current limit on the GX, and charge current limit of the Multi’s in VE.configure.

Those are the most likely causes to check first.

Does it charge at all from the AC PV? If you isolate the DC MPPTs and disconnect them, does any of the AC PV power go to charge the batteries?

Or does battery charging stop and all AC PV power flows out to the grid?

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jejochen avatar image jejochen commented ·

Hi,

The AC PV in connected on the AC IN, but as the inverter has no data connection of some sort, the EM24 meter is the only data from AC PV that is provided to the ccgx. So because i can't scan for the inverter, i have nothing to select.

There is no charge limit, as my battery can handle many times the max charge current the sytsem can provide. As in the picture below, the situation is always like this, even with low currents.

DVCC is not enabled, as i have no experience with it.

When the mppt's are off, the excess ac pv power gets charged via the multiplus 2's to the battery. When mpp'ts are switched on, the multiplus chargers seem to switch off.

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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ jejochen commented ·

There was an improvement made in the ESS assistant when a system included both AC and DC PV in multiphase systems.

Please update to the latest version of the ESS assistant in the latest version of VE.Configure and see if that resolves the issue.

Note this can be done remotely over the internet with Remote VE.Configure. Remember all 3 Quattros on all 3 phases must have the updated ESS applied.


Regarding the location of the PV inverters, you should be able to select this through the Energy Meters menu instead - though I now do not think that this is the issue:


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jejochen avatar image
jejochen answered ·

Hi,

Thanks for the respons.

I had the latest update, but loaded again the configuration file anyway. Result is the same. Some pictures added.



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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ commented ·

Hi @Jejochen,

There is a misconfiguration with the location of the AC PV inverter.

See the values in your picture,

-5000W exporting to the grid

5500W being consumed in AC load

5700W being produced by AC PV 'on input'

2400W being produced by DC Solar MPPT

2310W being consumed charging the batteries.


There is ~5000 W unaccounted for.


Please adjust the PV inverter position setting on the GX device to AC Output and see if that resolves the issue.

For a network connect PV inverter:

or for an energy meter connected PV inverter:

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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @Jejochen,

The limitation is with the battery, or the BMS.

It is sending the signal to the GX device that the maximum Charge Voltage Limit is 45V, and the Maximum Charge Current Limit allowed is 0A.

So the Multi's are not charging it.

I don't know what kind of battery system you are using, it does not appear to be one that is officially supported by Victron.

Please contact your battery supplier for support.


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jejochen avatar image
jejochen answered ·

Solved!

The issue was at the bms. Values in software were ok, but didnt seem to be transfered to the bms hardware. Now i redid the process, the system does use the excess ac pv power to charge, as intended. Thanks for the help, i was not aware the 3rd party BMS was the problem, as in the Victron software all values were ok...


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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ commented ·

Hi @Jejochen,

Good to hear that you've got the main issue sorted out.

I see that you moved your PV back to the AC input setting on the GX, and once again your produciton/consumption figures do not add up correctly.

This could just be due to a reporting delay between the components, but did you try moving it to the AC-output to see if that made the numbers correct?

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