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Nicholas Herbst avatar image

AC Coupling with non-Fronius inverters and export power limiting

Hi All,

Here in South Africa we are more often than not, required to prevent power being exported beyond the Meter (Grid).

We often encounter homeowners who have already invested in a solar power system, with some form of grid-tied inverter installed.

The typical upgrade involves installing MultiPlus or Quattro Inverter/Chargers with some form of lithium battery bank.

The question arises with regards to how we incorporate the existing grid-tied inverter?

If it is not a Fronius inverter, then we cannot use the "Fronius Zero Feed-In" functionality through using a single energy meter (Carlo Gavazzi ET112 or ET340).

If we retain the existing grid-tied inverter's export limiting device (current sensor or energy meter), and continue to implement an energy meter for the Victron system, then how should it be set up? Which device should be installed first in line? Should we set a buffer/threshold on one of the systems to ensure that they do not compete to achieve grid-power = 0 (or other set point)?

I foresee that the two different export limiting control systems will compete against each other and may result in instability and/or poor performance.


Any insights into this?


AC PV CouplingEnergy Meter
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Hi Nicholas

Did you find a solution to this ? Having similar issues with incorporating SMA with Victron under ESS, although I know from the literature only Fronius can be used with 'zero feed-in'. Will appreciate your comments. Thanks.

3 Answers
Matthew Walsh avatar image
Matthew Walsh answered ·

For all inverters besides Fronius, export limiting when the system is on-grid would be the function of the AC coupled inverter, for example the SMA you would need a SMA energy meter or a Home Manager 2.0 to limit export to the grid. Solis 1ph can use a CT connect to it and so on.

Correct, only off-grid can the Victron frequency shift to control an AC Coupled PV inverter output.

Alternatively, you can look into use Ignore AC input and base it upon battery voltage levels

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aleuli avatar image
aleuli answered ·

I had a similar problem with an Enphase system. What I did was to set the Enphase profile to "No export". This seems to have an internal parameter similar to ESS "Grid setpoint" but fixed at 50W, not configurable.

Then I did set the ESS "Grid setpoint" to 150-200W. This way when the panels start generating electricity and Consumption (Home loads - Solar generation) < "Grid setpoint". The Multiplus charger starts rising the load, and everything remains stable around the "Grid setpoint". When the charger gets to its maximum and combined with home loads exceeds the panel generation, the grid loading goes down and then around 50W the Enphase systems starts curtailing the panel generation.

the problem I have is that when the grid fails the Enphase CTs detect 0 load and the Enphase system commands a reduction to panel generation until it gets to zero. Will be testing a hack to work around this on the next days.


Best regards,

Alex V.

Santo Domingo

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mikeb avatar image
mikeb answered ·

Hi

Some grid pv inverters do have the frequency shifting or power reduction option with in them


might be worth looking in to each manufacturs. Inverter you come across to install and follow there set up or installation process for it


regards


mike

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Frequency shifting is the operation performed when the grid-tied inverter is AC coupled exclusively on the output of the Victron inverter(s) and DURING a Mains power failure.

The scenario that I am referring to is when Mains power is available and the system is operating in ESS mode, targeting a grid set-point of zero watts with circuits/appliances connected on both the input and output of the inverter.

Did you manage to find a solution?