Power oscillation on L1 only when peak shaving

Q&A and troubleshooting
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1

Hello,

I’ve been trying to diagnose this peculiar issue of power oscillation (power going up and down from 2500W to -1000W almost like a sine wave) only on L1, while L2 and L3 are unaffected when using multi-phase regulation set to individual phase (this is required by grid operator). If multi-phase regulation is switched to total of all phases the oscillation range is worse from 4000W to -3500W. This only happens when peak-shaving (set to always) is active and battery is at minimum or below minimum SOC. When the battery is charging there’s no oscillation and if high load turns on and battery is discharging (due to current limits) there’s no oscillation. This issue has been happening for a long time across multiple firmwares.

System:
3x MultiPlus-II 48/3000/35-32 (one per phase, firmware: 552)
Cerbo-GX (v3.52)
REC-BMS LiFePO4 battery (canbus)
AC, Grid tied PV inverter (SolarEdge)
Using external meter (it’s the utility meter, reading DLMS push data with refresh interval of 1 second)

Here are some readings I took from the MQTT:

Grid meter readings (showing all three phases, minimal load in the house)
Grid meter readings (showing all three phases, minimal load in the house)2026×474 48.4 KB

Grid readings when heat pump switched on
Grid readings when heat pump switched on2020×497 41.6 KB

Multiple readings for L1 only
Multiple readings for L1 only2023×454 76.7 KB

Here are screen captures when oscillation is going on:

1 Like
2

Same here. System:
3x MultiPlus-II 48/3000/35-32 (one per phase, firmware: v510)
Cerbo-GX (v3.55)
Pylontech Force L2 LiFePO4 battery (canbus, BMS)
AC-out: Grid tied PV inverter (Solis with meter ET340)
Victron MPPT RS 450/200 v1.22
Using external meter: EM24

3

After disassembling everything, I found that the issue was just a very slightly unclipped CT clamp on L1.

Have you tried these troubleshooting steps?

  • Do the oscillations still happen if you disable or remove the grid meter from the system?
  • Are the phases on the grid meter and Victron inverters wired in the same order?
  • Are any neutral wires connected externally?
4

Thank for your reply!

  • Yesterday it works for some hours using the internal meters of the multiplus.

  • Wiring of phases is correct.

  • Because the system works since 2023 until last Sunday without any problems, I think the wiring is OK (no changes made since 2023).

Tested in the meantime:

  • Update the Multiplus to newest firmware v556
  • Completly reinstall of the Multiplus using VictronConnect App and VE.Bus Configuration Software.

It does not help….

Next step I will reinstall the Cerbo.

5

Problem solved: The headphone socket (provided for an external current sensor on elder Multiplus-Modells) was faulty although not used in my setup. Some contact spray helps to eliminate the oscillations caused by wrong/random current measurements from the failing socket contact.

6

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