question

force-1 avatar image
force-1 asked

Behavior of Multiplus II with AC coupling on input

My current system consists of a grid tied Solis PV inverter and ~4,5kWp of solar. My main focus today is to compensate my grid consumption over day. Additionally I'm charging an EV when there is excess solar power available - I'm steering this based on grid-meter data with a Raspberry PI.

I want to enhance the system with a Multiplus II and a batterie now.
After reading tons of documentation and watching videos, I'm not sure about the exact behavior of the system in case I would connect the PV inverter on AC input of the Multiplus II.

My current understanding would be the following:

  • The existing AC PV inverter will directly power the loads as today
  • In case the Multiplus detects negative consumption (feed-in) at grid meter, it will start to load the battery - aiming for zero consumption at grid meter
  • If the batterie is full, all excess power from the PV inverter will be fed into the grid as the Multiplus is not taking any power
  • If the Multiplus detects positive consumption at the grid meter, it will provide power from the battery (if possible) and aim for the grid setpoint (e.g. 0W)

Is this understanding correct?
Would I need to install the ESS assistant in this case or do any other configuration?

Multiplus-IIAC PV Coupling
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1 Answer
petr avatar image
petr answered ·

@Force_1 yes, you would need to install ESS which works exactly as you have described.

In chapter 2.1.2. System examples the diagram shows your case where ET340 is used to measure the grid and a single-phase PV Inverter. It should also be mentioned that the ESS setting requires the correct grid code setting, which has other implications. It should be done by qualified personnel and typically requires approval from your energy distributor and the fulfillment of a bunch of other requirements from its side.

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