I have a rare situation where I have the capability to feed the grid with a diesel generator(goal of running alternative fuels). I have 3 x multiplus II 48/5000 in 3 phase configuration. I have been experimenting with how the generator interacts with the multiplus. I run ess and as far as the multiplus is concerned its an AC coupled grid feed PV.
For a while i had the generator connected to the AC OUT 1 as well as the loads and pv inverters (15kw and 8.2kw fronius). This was due to wiring limitations(single overhead to the shed with and gen and pv) After testing and extensive tuning, I had the system running seamlessly even in a grid failure situation. Thought I was clever. The issues I started to run into after a while were when trying to feed the grid harder and due to VAr fluctuations would reach the limit of the 50A transfer realy and trip the multiplus. I could not get the VAr’s any more stable due to the response limitations of the digital AVR.
I then started switching the bypass before grid feeding, essentially putting everything on the AC IN of the multiplus. This works well but requires physical switching. The cheap generator changovers you get off ebay are not a good idea, they seem to catch on fire and force you to replace the whole panel. Lesson learnt. I also had one unexpected multiplus trip when I lost the grid early morning with the batteries low, showing 0% by the time I woke up and noitced. When the generator contactor closed the multiplus immediately tripped on overload, as i didnt have high speed loging running i have no idea as to why and I havnt been able to recreate. Not as reliable as I hoped.
I am now going all out. Underground conduit, 4 core 50mm2 to the generator to a supply bus(grid, diesel gen), 4c16mm2 for the loads and PV from the multi. Latching grid contactor controlled by generator system as well as active export control. If i want to export 35kw because the price is good, thats what I get regardless of loads, if I loose or gain loads the generator compensates. Im moving most of the critical and safety i/o to an industrial PLC, previously node red(ngl has been great). Also the ability to change from generator to grid without power loss as it can then sync the whole system.
The reason Im reaching out to the community is I realy like the victron dashboard and an wondering if it can be tweaked for my use case. It does almost everything I need and when the current upgrades are finished Im going to have a go at building a generator driver for the dbus. But, I havn’t even found a hint of how I can get VRM to except that the grid and generator are both connected. When you signal AC IN is now a generator I lose the grid Metrics and vice versa. Unless it will change with the driver but adding a power meter for the generator to the system didn’t help. Best I have so far is calling it a PV inverter but its hard to differentiate between that and the real PV on the dashboard.
Im also happy to answer any questions and would love feedback on where I can improve. Sorry for the long read.
Yes it can. It only failed the once and I wish I captured the data to see why. It was good because I could run the generator in grid mode and the multi would regulate the output with frequency.
With both the grid and generator connected, have you tried enabling AC Input 2 in the Venus settings? Then, write the proper generator meter readings to the DBus registers.
The generator itself is nothing special. Old volvo engine with a 110kw cat altenator. I use a Basler DECS 100 avr with a Dawson Technology(now Heinzmann) Sitec Xtend CGC control. I had to do some weird CT trickery to get it to work nicely with such a small generator. It could also be done with some Woodward modules if your looking for something easier to obtain, let me know if your interested and I can help you with exactly whitch modules and how to get it going.
I never considered activating the seccond AC IN because the multiplus doesnt physically have the capability. Thank you so much for the suggestion, I will give that a go.
I already use grafana for viewing data. VRM is just such a nice dashboard and consolidates the daily data so effectively and for spot checks on the system.
With both the grid and generator connected, have you tried enabling AC Input 2 in the Venus settings? Then, write the proper generator meter readings to the DBus registers.
You would also need to tell the system to use AC in 2. But all of the parameters you’d need to change are read-only on dbus (written only by the creator (the VE.Bus device).
I added code to accommodate an external transfer switch ahead of the AC input that might be a start. It’s part of GuiMods.
In your case however, you aren’t using the AC input to feed the generator into the system so there will likely be additional tweaks needed especially since you are using both grid and generator at the same time.
That you for the advice. I’m excited that it sounds like a possibility.
Another question regarding my situation. Is there a way to leverage the multiplus power factor? As I have a to generate VAr’s when the generator is online it limits my export kW to the maximum current of my grid connection. I currently bring the generator to 0.95PF under load but that still forces me to export the overhead VAr’s.
In an ideal world I would have ESS(or other system) read the grid meter and try and keep the export PF at 1.0 by commanding the multi to absorb VAr’s but I would be amazed if that were a possibility. Failing that external control over the multi’s either VA’s directly or a charging inductive power factor as I’m usually charging at full power if the generator is running. Charging has sort of been a double edge sword increasing the generator load thus increasing VAr generation.
I don’t mind sacrificing multi charge power as I also have a bank of chargers that I stage to keeps the battery bank within acceptable limits.
My only other option is to try a 1.0PF when generating at full power and hope that I still have headroom before pole slip. I feel that I do as I push the system voltage quite high (~248V) at maximum export current so I still have a decent excitation voltage but it goes against good practice.
I would love to know your thoughts. You guys really seem to know your stuff. I hope I can return the favor somehow.
