House 1 contains lot's of panels, MPPT chargers, batteries and a 5kW Multiplus.
House 2 contains some panels, MPPT chargers, batteries and a 3kW Multiplus.
Can I chainlink the two Multiplus inverters? AKA can I connect the AC input of the 3kW Multiplus inverter to the AC output of the 5kW Multiplus and feed it energy? Will I damage anything?
It is known as cascading, it not an officially supported setup.
The main consideration is the inout current limit and makong sure you down overload the first one mostly. And not back feeding as the firstone cannot control the second one.
"it not an officially supported setup"
but it will work, right?
"And not back feeding as the first one cannot control the second one."
Does this mean absolutely no backfeeding or little backfeed is ok? Will grid assist on the "slave" inverter hurt the "master" inverter?
I understand cascading is not a baseline configuration but assuming both systems are totally independent in their components, the only thing connecting them being the AC-OUT to AC-IN connection, and assuming adequate configuration, I can't see why there is a reason for this to not be feasible and fully functional. The key question is, as you mentioned, potential back feeding, and what is the right configuration for the specific use case.
The option of paralleling the two systems is, in my case, not feasible, as they are 40 meters away [I know the advantages and configuration of // as my current system has 3 Multipluses II].
I'm not familiar with ESS as my system is currently off-grid and I'm using DVCC but when cascading, the downstream system is not off-grid anymore as its AC-IN is now connected to a grid. The upstream system is indeed off-grid and DVCC configuration with generator start/stop is a perfect [and supported] configuration. My thoughts are that configuring the downstream as ESS with zero feed-in and ESS settings as required such as "keep SOC at xx% level etc." is a possibly good solution.
In my case, as the overall installation is still obviously off-grid, I can never run out of battery energy and below a given SOC the generator kicks in. So if I program the ESS of the downstream to never let the battery go below say 50%, if there isn't enough PV energy available, it will ask the upstream to provide energy, until the upstream SOC goes below it's own configured level which could be 20% and then it instructs the generator to start. So the upstream is "only" depleted when there is a need which is why it is there in the first place. Those % numbers are arbitrary and would need to be tuned to the specific situation.
So the question is; what do you think about a cascading system like this where the downstream is configured ESS, the upstream DCVV, and the generator as backup?
Back feeding shouldnt be an issue, because it is easily turned off in setup.
To be fair I expect backfeeding from one multiplus to the other could work, as opposed to a generator backfeed being a bad idea all round, but AC Coupled Solar, with/without ESS, uses a frequency shift to throttle the solar chargers and I am not aware of a way in which a multiplus could be forced to act like that. I decided to disallow any form of back feed on either inverter so simply dont have to eal with it. BTW I also have auto changover switches round both inverters so I can feed the property from either unit or directly from the genny.
Just to clarify M system is configured...
Genny > 48/5000 with DC PV > 24/5000 > Distribution
Both MP's have 100A transfer capacity so I can supply circa 11.5 kW to loads comfortably with the genny running and could in theory do much more with a larger genetator.
I havent had any issues other than some instability caused by a less than ideal generator, when cold at least. I currently have weak AC set on both MP's, beacuse that is sesigned to limit th rate at which the AC In load is changed but I am going to revisit my AC settings because I think the odd isssue I do see is a result of both MP's trying to compensate for the same change in load. My plan is to ramp the generator up slowly and then keep it at a stable load if I can. I think Week AC is actually causing issues now.
Enough of that sorry dont want to hijack your thread.
