question

ralfz avatar image
ralfz asked

MultiPlus-II ESS Mode 3 stuck in Passthru

Setup

I have a new setup with a MultiPlus-II connected with a MK3-USB to a Raspberry Pi with Venus OS on it. I want to use the MP2 in Mode 3 in order to implement my own control loop on the Raspi.

On AC-in, the mains of the house is connected. There, I have a Fronius Symo with PV installed. The remote console shows the PV inverter and the power flowing. Currently, there is a 48V LeadAcid AGM battery connected to the MP2, the MP3 shows it at 100% SOC.

With VE Configure 3, I have configured the following:
- Grid code: "Germany VDE-AR-N 4105:2018-11, internal NS protection"
- LOM detection"TypeB (grid code compliant)

I want to control the Mode 3 via dbus. I wrote a Python script but failed. On the remote console in Settings / ESS / Mode, I selected "External control" in order to use Mode 3.

Now I am trying a bit more basic to see if I have the MP2 under my control - using dbus-spy.

I see com.victronenergy.settings/Settings/CQwacs/Hub4Mode=3 as expected.
I can change the value of com.victronenergy.hub4/AcPowerSetPoint and com.victronenergy.settings/Settings/CGwacs/AcPowerSetPoint with the help of dbus-spy. When I change one of those values, the other follows directly.

Problem

No matter what I do, the remote control always show "Passthru" for the mode of the MultiPlus-II. It is totally passive.

When I do a rest of the MP2 (via Advanced / System reset), the mode changes from Passthru, via Off to Inverting. The MP2 actually takes 35W from the battery. After about 15 seconds, the remote console shows an alert "Grid lost", a little bit later, the mode is back to Passthru.

The 35W inverting power is not according to what I enter as AcPowerSetPoint. It is always 35W, no matter if I enter 0 or -200 or -500 for the AcPowerSetPoint.

Question

So it seems as if there is something wrong in my setup. I clearly have no control via Mode 3.

I hope somebody can give me a hint on what I am missing in order to make it work.

Multiplus-IIESS
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1 Answer
Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @RalfZ

I'm moving your post to the 'modifications' section as there is more knowledge about this there.


What I can tell you:

-first try ESS mode 1, if that works, mode 2, etc. take it step by step so you can find where things get stuck.

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ralfz avatar image ralfz commented ·

My current setup and configuration

I am now working with mode 2 and it somewhat works.

I am enhancing my driver for the Fronius SmartMeter (GitHub) with two control loops. One for charging and one for discharging (zero power from the grid). As described in (ESS mode 2 and 3), I am using dbus to control the following paths:

  • com.victronenergy.settings /Settings/CGwacs/ AcPowerSetPoint
    (Grid power setpoint)
  • com.victronenergy.settings /Settings/CGwacs/ MaxChargePercentage
    (Enable/Disable charger - 0 or 100)
  • com.victronenergy.settings /Settings/CGwacs/ MaxDischargePercentage
    (Enable/Disable inverter - 0 or 100)

The discharge loop works somewhat ok. I am surprised.

The charging loop has some issues, especially around the higher voltage area.

I have a 48V LiFePO battery connected and have configured everything with VE Configure 3. The AC-in of the MultiPlus-II is connected to one phase of my houses installation. The AC-out has nothing connected.

The Problem

Here are two examples of things going wrong:

  1. The battery is around 51.5 Volts and my script sets AcPowerSetPoint to 100. Typically, the MulitPlus-II then only charges the battery with 30 to 50 Watts.
  2. The battery is around 52.0 Volts and my script wants to stop charging, so it sets AcPowerSetPoint to 0. Within a time of several minutes, the MultiPlus-II slowly reduces the charging current from 50 Watts down to 10 Watts. And it takes probably 20 minutes for the current to/from the battery actually reaches 0.

These two examples show, that I am not fully in control of charging. The charge current does not quickly follow the AcPowerSetPoint input. This gives a risk of over-charging the battery.

Questions

  • What is the algorithm running in the MultiPlus-II that gives me headaches here?
  • Is there anything that I need to deactivate or switch off in order to get the transparent control over the charging current that I need?


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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ ralfz commented ·

Hi @RalfZ

You don't control your battery limits by you AC limits!! control your battery limits on the battery side of things, and in a (semi) hardwired way so the system cannot overcharge in any event.

simple: 2 signal BMS (enable/disable charging / discharging)
more advanced: CANbus connected BMS

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