SMA SB 1100 grid-tie inverter connected to Victron Multiplus AC input - off-grid????

[seminalpolemic]

Hello,
I am off the grid. I recently acquired a Victron Multiplus inverter/charger. Apart from the high quality inverter, it has a very sophisticated battery charge management system but I can't use it because I have a 24v DC from my solar array and the charging side of the multiplus will only receive 240v AC from say a genset. I don't want a genset, but I still want to use the Victron multiplus charger by rewiring my array to 146vDc and putting it through SMA sunnyboy 1100 grid-tie inverter which is connected to the 240vAC input side of the Multiplus. Will this work?
Regards,
Seminalpolemic

[inetdog]

Hello,
I am off the grid. I recently acquired a Victron Multiplus inverter/charger. Apart from the high quality inverter, it has a very sophisticated battery charge management system but I can't use it because I have a 24v DC from my solar array and the charging side of the multiplus will only receive 240v AC from say a genset. I don't want a genset, but I still want to use the Victron multiplus charger by rewiring my array to 146vDc and putting it through SMA sunnyboy 1100 grid-tie inverter which is connected to the 240vAC input side of the Multiplus. Will this work?
Regards,
Seminalpolemic

You can use a SunnyIsland directly to provide the AC, although you may need to add a transformer on the output if you also need 120 or the inverter requires a balanced 240V system with a neutral.
You can use a SunnyIsland or other off-grid inverter to provide the necessary AC reference signal to a SunnyBoy grid-tie inverter as a hybrid system.
You cannot operate a SunnyBoy without a stable AC reference source which either can absorb unlimited power or can provide throttling feedback to it.
That means, in the simplest form, either a SunnyIsland or a utility.

[Conicsection]

Victron Multiplus to provide a grid signal

You can use a SunnyIsland directly to provide the AC, although you may need to add a transformer on the output if you also need 120 or the inverter requires a balanced 240V system with a neutral.
You can use a SunnyIsland or other off-grid inverter to provide the necessary AC reference signal to a SunnyBoy grid-tie inverter as a hybrid system.
You cannot operate a SunnyBoy without a stable AC reference source which either can absorb unlimited power or can provide throttling feedback to it.
That means, in the simplest form, either a SunnyIsland or a utility.

I have some information that appears to conflict with this, but I have been trying (so far without success) to understand how it works. I am trying to design a system that does exactly this.

Please follow this link to Victron Energy's 'Off Grid' leaflet: http://www.victronenergy.com/upload/...ems_EN_web.pdf

If you turn to page 15, you will see a system design that uses a Victron Multiplus to provide a grid signal to a Blue Solar grid tied inverter. The claim is that the Multiplus can use the AC provided by the Blue Solar to charge a battery bank. And if you look at the diagram it appears that Multiplus and the Solar Inverter both connect to a common AC bus. For ease of reference I set out below the text that accompanies this:

AC Systems
For larger solar systems that generally supply to AC consumers, it is more efficient to immediately invert the solar power into AC.
Therefore we call these systems “AC systems”. AC systems have a higher energy efficiency in comparison to DC systems. The
BlueSolar Grid Inverter directly converts the solar energy into AC. This inverter requires ‘grid’, which is provided for by a MultiPlus
or Quattro. All excess solar power which isn’t used by the AC consumers is used to charge the batteries.


If this works it is a fantastic idea!

[Conicsection]

More information

I have done a bit more research, and this link may be useful: http://www.victronenergy.com/blog/20...stants-update/

Scroll down to 'PV Inverter Support'.

It appears that the Multiplus and Quattro can be configured (using Victron's VEConfigure program) to regulate the output from a PV inverter by varying the frequency of its AC output.

Very interesting.

[inetdog]

I have done a bit more research, and this link may be useful: http://www.victronenergy.com/blog/20...stants-update/

Scroll down to 'PV Inverter Support'.

It appears that the Multiplus and Quattro can be configured (using Victron's VEConfigure program) to regulate the output from a PV inverter by varying the frequency of its AC output.

Very interesting.

Unfortunately, not all GTIs are designed to vary or clip their output based on the "grid" frequency.
SMA Sunny Boy are designed this way, since that is how they interact with the SMA Sunny Island.
If you choose to use any particular brand/model of GTI with the Victron, make sure that it is built to work with frequency signalling!

[paulcheung]

Hello,
I am off the grid. I recently acquired a Victron Multiplus inverter/charger. Apart from the high quality inverter, it has a very sophisticated battery charge management system but I can't use it because I have a 24v DC from my solar array and the charging side of the multiplus will only receive 240v AC from say a genset. I don't want a genset, but I still want to use the Victron multiplus charger by rewiring my array to 146vDc and putting it through SMA sunnyboy 1100 grid-tie inverter which is connected to the 240vAC input side of the Multiplus. Will this work?
Regards,
Seminalpolemic

Why you want to do that? The more inverter you going to use, the more energy lost during the efficiency effects. Why don't you get one of those good quality Charge controller like classic 150 or the Outback FM80 or 60. Those quality controller has all the features that off grid people wants.

Cheers

[Conicsection]

My reason is that my panels will be on the flat roof of my houseboat. I do not want the weight of a battery bank on the boat. So that means a long cable run to my garden shed of about 70 metres, the nearest practical site for batteries, inverter and generator.

So I decided on inverting to 240v on the boat, and a 16mm cable to the shed.

I agree there are losses, but I can't think what else might fit the practicalities.

If anyone has any other better solutions I would be very pleased to hear.

[inetdog]

My reason is that my panels will be on the flat roof of my houseboat. I do not want the weight of a battery bank on the boat. So that means a long cable run to my garden shed of about 70 metres, the nearest practical site for batteries, inverter and generator.

So I decided on inverting to 240v on the boat, and a 16mm cable to the shed.

I agree there are losses, but I can't think what else might fit the practicalities.

If anyone has any other better solutions I would be very pleased to hear.

Well, one simple solution would be to get a CC with a high voltage DC input, located at the battery bank and rewire your panel array to series to get the maximum DC voltage and minimum current.

This will be more efficient overall than going through the GTI and Victron combination.

I also have doubts about whether the Victron can both charge and invert at the same time. You would have to have that capability to provide a reference for the SB. Without very special programming and extra hardware, using the AC output of the inverter to charge the batteries the inverter is drawing from is just not going to be stable.

[Conicsection]

Well, one simple solution would be to get a CC with a high voltage DC input, located at the battery bank and rewire your panel array to series to get the maximum DC voltage and minimum current.

This will be more efficient overall than going through the GTI and Victron combination.

I also have doubts about whether the Victron can both charge and invert at the same time. You would have to have that capability to provide a reference for the SB. Without very special programming and extra hardware, using the AC output of the inverter to charge the batteries the inverter is drawing from is just not going to be stable.

Well, I am slightly worried by your reply as it echoes some of my concerns. But without doubt the Victron documentation clearly includes this setup. I even downloaded the software VEConfigure, and all the settings to do this are there.

I presume that the way it works is for the charger and inverter to be completely isolated from each other, and in this state the charger must act as if it is another AC service. That way it would be possible for the inverter to operate at the same time as the charger.

As regards your DC CC solution, I guess that would work but then I would have to have two long cables, one carrying DC and the other returning AC to the boat.