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force-1 asked

ESS mode 2: Where is grid power setpoint measured

I would like to use ESS mode 2 to control the power output of my Multiplus 2 without having the need to implement my own control loop.

For ESS mode 3 it is stated in documentation, that the value written as Grid power setpoint is measured at the AC input of the device. Meaning that setting a -100 will feed 100W back from AC input.

For ESS mode 2 this is not as clear for me. From the documentation I read that the Grid power setpoint is the value the Multi will try to match at the grid meter with it's own control loop.
Setting the grid power setpoint to -100 would then have no meaning for the AC input as it would depend on loads connected on AC input. If e.g. a 500W load is active on AC input, the multi would output 600W then to match the grid power setpoint of -100.

Is that understanding correct?


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johnone answered ·

In the 'ESS mode 2 and 3' doc, there is the following description:

https://www.victronenergy.com/live/ess:ess_mode_2_and_3

"In Mode 1, standalone operation, the ESS control system tries to keep the power flowing through the grid meter at 0 Watt (so no power is taken in from the grid, nor is any power fed back to the grid). Mode 2 means you actively control the target for the grid power. Setting the target to 100 Watt means that the system tries to take 100 Watt from the grid. The power will be used to feed the loads or charge the battery. Similar, a negative value will instruct the system to feed back power to the grid. This will be PV power when possible, otherwise the battery will be discharged. Reset the setpoint back to 0 Watt, and you are back in standard mode again."

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force-1 answered ·

Thanks @Johnone - I got my current understanding from the linked documentation.

Still it's not clear to me if the semantic of Grid power setpoint is different between mode 2 and mode 3. Has anyone more insight on this topic?

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johnone avatar image johnone commented ·

Ok, I quoted the above from the docs as I thought it's where Victron are being unusually clear in explaining the different Modes. I think, now, I can see the ambiguity you point to. Are they referring to an 'external' grid-meter or the grid-meter in the Multiplus (ESS can, of course, be designed without an external meter)? Maybe if you described in more detail what you want to achieve that would help?

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force-1 avatar image force-1 johnone commented ·
Actually I want to avoid that my B16 circuit breaker will trip.

As my PV inverter coupled on AC input can delver 3,6kW (which is 16A on it's own), I want to make sure that the sum of ampere delivered by the MP2 and my PV is 16A max.

For this I plan to have the PV power (measured via ET112) as the guiding number and just 'add' output from MP2 depending on the load as long as it doesn't exceed the 16A/3,6kW in total.

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