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Feature request: PV inverter on two phases of a three phase multiplus 120V system

Our grid is 3 phase, 127V phase to Neutral and 220V phase to phase. We install three-phase multiplus-II systems with single phase 220V PV inverters by connecting to any two phases of the three-phase system. When we setup the PV inverters on the Cerbo, we can only choose either a three-phase inverter, any one of the phases or split phase on phase 1 + 2. We would like the option to be able to connect to any two phases. For example phase 1 and 3. Also, the PV Assistant does not work in this case for some reason, so we must use the virtual switch to limit the PV output when the battery reaches a pre-set voltage level. We would rather use the assistants, as we also wish to use assistants to control the Aux 1 relay on the Multiplus.

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·
What PV inverter? What sensor do you use to measure the PV power?
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Mike Dorsett answered ·

single phase 220V PV inverters by connecting to any two phases of the three-phase system

This will not comply with the installation requirements of many single phase 220V inverters, which require the Neutral Earth voltage to be less than 127V AC (normally ~0V).


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ip-solartech avatar image ip-solartech commented ·

All 220V inverters work perfectly on our grid. Hundreds installed here since 2013. Inverter brands which require Neutral-PE voltage to be less than 30V (such as all SMA inverters) have an option to Ignore PE monitoring, which we simply switch on.

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ip-solartech answered ·

The PV Assistant instructions indicate to install the assistant as the last item and also to install it on all three multis on a three phase system. I've don't just that, but it simply puts the system at the 52.7Hz no matter what the battery charge is. The PV assistant instructions also indicate to load the assistant on L1 when there are assistants combined with the PV assistant which control incoming AC, which is the case with this particular installation. So I've then loaded the assistant only on L1 and have the same result. I've switched back to using the Virtual switch to control accepting AC and to control frequency when the battery is charged. This does work; however the Virtual switch has the frequency either at 50hz or 52.7hz. There is no ramping up like on the PV assistant. We also wish to use the generator start/stop functionality of the Cerbo to control the AC input and the PV assistant to control the inverter dynamically.


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