Multiplus @ FRONIUS - DC Ripple

Q&A and troubleshooting
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1

Have an offgrid 3 phase system, and the multiplus isn’t controlling the Fronius well. Connected via a hardwire ethernet cable, so it should have fast direct control not just frequency shifting.

Correct microgrid setting on fronius, PV assistant setup on all 3 multis.

  1. SOC is 100% or 99%
  2. Peak sun
  3. Connect large 11kw 3phase load.
  4. System is NOT frequency shifting despite battery SOC being high, its at 50 hz.
  5. Frequency was higher, like 52hz earlier, without large loads
  6. a large AC load disconnects (the 11kw car)
  7. Fronius keeps injecting 10kw AC power
  8. batteries full
  9. AC output spikes to 260 volts
  10. DC ripple alarm
  11. system resets
  12. System shifts frequency up but not fast enough

The fronius is connected via a wired ethernet cable, so it has instant communication with the cerbo, not just the frequency shifting.

Why is it calling for the fronius to product power when the SOC is so high?

Anything over 95-97% SOC it should tell the fronius to stop.

How can I do this without getting into custom node red programming?

thanks!!

2

ESS Assistant have a parameter called “Voltage to restart PV“. Play with that value to be around your battery 85-90% SOC.

For my system, with 16S battery, this parameter is set to 55.00 V and up to now, I’m happy with it.

PV inverters on AC OUT are controlled solely by frequency shifting.

Make sure to have same frequency values for “start reducing“, “reduced to minimum“ and “disconnect”, in ESS Assistant and Fronius inverter(s).

The Modbus_TCP part is for controlling the export energy only.

Sorry for reviwing old post !