Victron Multiplus with Sunnyboy sync

[LourensJB]

I am not sure if this has been covered in other threads here - if so please refer me to the correct thread.

I have a new installation with a Sunnyboy PV inverter with a Victron Multiplus 48/5000 charge controller. It 8s up and running after loading the correct assistants and settings. What happens under certain conditions is that the PV inverter gets stopped via adjusting the frequency of the output power by the Multiplus. This is when demand has almost stopped or lowered significantly. The PV inverter then supplies only a fraction of what it could based on available sunlight. This is apparently normal.

However when demand increases again through switching on appliances etc the PV inverter 8s not triggered to increase its supply and the Multiplus supplies from batteries. This will and has discharged the batteries far lower than what is safe for them while there is up to 3kw available via the PV Inverter.

I can rectify this only by switching off everything and restarting the Multiplus and then the Sunnyboy and then apply load. How is this situation rectified and the Sunnyboy put into operation again automatically when demand increases?

Any help or explanation would be sincerely appreciated.

[Wetkit]

LourensJB,

I have seen installations like yours, and it is really complicated to figure out the exact cause.

Who did the unit programming and set-up?

Where is the PV invertor connected in relation to the Multiplus? Before it or after?

I would also like to know the reason you went this way, as it is very costly, if I may ask.

[LourensJB]

The reason I wnt this route is due to being a direct Eskom client in a rural area. We are being charged for network and support which is n9t lj ked to consumption so one cannot bring that fixed cost down with using less energy. In effect I have paid more than R4-30 per kwh before the latest increases. So yes it is very costly but it makes financial sense to go off grid completely.

The way it is being connected is PVPanels - SB inverter - Load. Then from the other side: Batteries - Multiplus - Load. So in essence the MP and the SB is in parallel over the load. Not one before or after the other. I have a Victron Current sensor over the Live AC output.

The basic setup was done by the suppliers technician here in Pta.

[Wetkit]

Ok, just to make things clearer, I have made this simple drawing.

 

 

Are your system connected according to A or B?

If you running system A, what position is the current sensor connected, 1 or 2?

 

I'm just speculating here now....

System B will have the least amount of issues, but will not be able to use any PV power during load shedding or power failures, so I would think the system is connected according to A.

 

Now with system A, the idea is that once load shedding occur, the PV will supply as much power as it can while the Victron invertor supplies the AC required for the PV system to stay functional.

This will also lower the draw on the battries, but this is only during the day.

 

Now with this added current sensor the problem gets a bit muddy....

Logic tells me it should be connected to position 1, but then why is it needed, as the Victron unit surely must know the draw through itself???

If the current sensor is in position 2, it will be measuring the output of both devices, PV and Victron.

So if there is not enough draw, the current sensor tells the Victron to up the freq, thus reducing the PV output, fine.

So now when demand increase, the Victron unit supplies it, but not triggering the PV to start re-supply.

If this is correct, it can only mean there is an issue with the set-up programming of the Victron unit.

Perhaps the upper and lower thresholds is not programmed correctly, or, it pushes up the freq too high, way above the limit of the SunnyBoy, and disabling it.

 

Next time it happens, restart the SunnyBoy first. Give it 5 min to stabilise. Does it display the system freq?

If nothing changes, bypass the Victron. Look again at the system freq on the SunnyBoy, while the Victron is on bypass.

Did it work?

 

It is either a setting on the Victron unit that is not correct, or the current sensor is in the incorrect location.

 

[LourensJB]

Thanks for the input Wetkit...

 

The system is wired according to A but the current sensor is in position 3 as shown here: 

 ( http://powerforum.co.za/index.php?app=gallery&module=images&section=img_ctrl&img=31 )

 

As this only happens once the batteries has been fully charged (Multiplus not directing large current to the batteries itself) I will see if I can duplicate the error tomorrow when I am close to the system. The same thing happened today while I was out so I am just charging batteries now. I don't think I will have enough sun left to play with today still.

[Wetkit]

That is a weird position for the current feedback sensor.

In that position it only senses the output of the PV invertor and not the load.

While your battries is charging, the PV can feedback power to the Victron unit, bat now when the battries is full, the PV unit is throttled, no matter the load???

Not sure I understand the logic correctly here.

 

If it was me, I would go back and request the installer give me an explanation of how the system is supposed to function and operate.

Personally, I think they have that current sensor in the incorrect location, or their logic is flawed how they controlling the PV invertor via the Victron unit.

[LourensJB]

Tx for the input Wetkit... I will follow up this morning.

 

According to the below however the wiring is correct. The logic to me is that this way it can sense what the PV Inverter specifically is contributing :

 

Installation

1. Pull one of the AC wires of the PV inverter through the AC Current sensor.

2. Connect the sensor to the AUX or TEMP-sense input of an Inverter, Multi or Quattro in the same phase as being measured by that current sensor.

3. Configure the power range with the dipswitches. Select the power equal or higher than the maximum expected power. For example, with a 4kW PV installation, the correct dipswitch setting is 5kW. 4. Multi-phase installations: add one AC current sensor for each phase of the PV inverter. Wire it to the Multi in the same phase."

(From http://www.victronenergy.com/upload/documents/Manual-AC-Current-sensor-EN.pdf)