Multipluss II limited grid feed instable

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polly-nowak asked Jun 13, '23

Multipluss II limited grid feed instable

I have my Multiplus II 48/3000 configured the Cerbo-S GX (FW 2.88) to feed PV excess to the grid, but with a limit of 600W. However, the feed in is not stable. It goes to -600W feed in, and then reduces roughly back to the grid setpoint, then it goes up again to -600W, and back down, and it keeps looping like that. If I set it to unlimited feed in it works with a constant feed in of -2300W and no drops whatsoever.

On the DC side there are several Victron MPPTs all controlled externally by the GX and a 15kWh Battery, so there is enough DC Power available for a stable feed. What did I do wrong?

Multiplus-II feed-in limit

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Answer 1 · 2023-06-13T15:36:28Z

matt1309 answered · Jun 13, 2023 at 03:36 PM

Hi @Polly Nowak

Try enabling shared voltage sense in DVCC on cerbo gx?

I had similar issues where MPPT would turn on and off repeatedly when reaching the Maximum feed-in limit. Which for me just resulted in small peaks in battery voltage but maybe in your setup/with more MPPT's that's overflowing to AC side? Long shot but maybe the cause.

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Answer 2 · 2023-06-14T00:16:10Z

polly-nowak answered · Jun 14, 2023 at 12:16 AM

Thank you for the reply. I tried it, but unfortunately, it did not solve the problem.

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matt1309 commented · Jun 14, 2023 at 08:02 AM

Guessing you've tried this but checking connections on MPPT to cerbo, and maybe just giving everything a reboot. SVS was what sorted it for me.

Can you see anything unusual happening on the DC side. Do the spikes correspond with MPPTs turning on and off?

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polly-nowak matt1309 commented · Jun 14, 2023 at 05:03 PM

The problem isn't that new, so I tried a few hardware things. The issue remains eventho I replaced MPPTs, rewired them. I rearranged the strings. And it isn't that the MPPTs turn themselves off. They just all go down to a few watts to meet the requirements of the AC Home Load. The Zero Feed in works absolutely flawless. The MPPTs work at high, and mostly stable power as well, since we have cloudless sunshine since more or less a few weeks. Until the Battery is charged at least. Then everything cuts back. If I turn on a high load like an oven or similar Loads, the Multiplus II delivers constant power to keep the AC Meter near zero and the MPPTs all fire up to prevent Battery discharge. But as great as all of that works, the limited excess feed in remains unstable. Unfortunately the Datalogging of VRM is to slow to tell whether the Multiplus is following the MPPTs or the other way around. Maybe I should invest in a PDA.

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