Hello,
I’m trying to improve a system which is supposed to power construction sites with no grid connection. The setup consists of a 20kVA generator, a 3 phase Multiplus-II 48/5000 configuration and Pylontech US3000C batteries.
The problem is, that the test construction site mainly uses 230V heaters, so there’s a lot of phase imbalance. When the generator is running, the Multiplus-II doesn’t go into overload because it passes the generator power right through, but the imbalance is so big the generator itself shuts off.
Is there any way of “smoothing” the load on all phases using the Multiplus-II, so the generator sees at least somewhat symmetrical power draw?
I’ve read about phase balancing in an ESS, but that’s not applicable in this kind of system.
Hi. You could try limiting the Input Current to the Multis, to where the heavily loaded phase will Power Assist from the batteries.
You’ll have to watch you don’t exceed the capability of the inverter when assisting. And of course keep an eye on the battery, but the other phase Multis should step up there to charge them, also helping with phase balance.
Hopefully you can find a sweet spot that the genset is happy with.
In my humble opinion you need to address the load situation or get a larger generator. Could you run three of those electric heaters, distributed across the phases, and each set on a lower heat setting that would match the output of the one or two causing you the phase imbalance?
Resistive heaters use a LOT of power, as you know. This might be a case for using fossil fuel heaters if you have access to that fuel. If none of these ideas are practical, then I think you’ll need a larger generator (within the limits of the transfer switch of the inverters) and/or inverters to handle the loads.
When the input current limit is set accordingly it will do exactly what I need it to, but what will happen once the batteries are (almost) empty? One time the input current limit of the setup was set lower then what was needed on the output, it drained the batteries and a colleague asked what would happen once the batteries were empty. This was way below the generator’s max output, what would happen?
It’s for a construction site, so I can’t know on which phase the load will be, the workers could plug in any load at any socket
Sadly I can’t address the load situation. It’s for construction site powering and I can not influence how the load is distributed (some worker plugs in a heater in the first socket he finds).
And it’s not one heater overloading the system. You see, we provide a 32A socket for power for this system. Usually, there’s a container plugged in to the socket, sometimes more containers are “bridged”/connected to the first one. The distribution boards in those containers are wired exactly the same, 230V-socket 1 is L1-N, 230V-socket 2 is L2-N, 230V-socket 3 is L3-N. So if one is the easiest to access, all the load is on there.
The generator could power everything no problem as far as total power is concerned, it just cannot take the phase imbalance.
For reference, once there were 800W drawn on L1, 7600W on L2 and 1300W on L3. So I would like to know if there was some way of “buffering” the AC-IN using the Multiplus-II
Unfortunately there is no easy fix for an off-grid system. I have a three phase system with three 48/5000 inverters that runs one side of my shop. Everything is fine until I plug in my Tesla. In the USA, it’s extremely rare for a residence to have three phase power, so all of the passenger EVs in our country only have single-phase chargers built in to the cars. So when I plug in my EV to charge at my shop, I draw power from two phases while the other inverter is lightly loaded.
As you said earlier, this is fairly easy to solve by running ESS and “balancing” the phases by way of a utility connection. But you can’t do that easily without the grid, meaning you likely need a generator large enough to supply the max power any single phase could draw, larger inverters, or both.
Does anyone happen to know if there is such a thing as a three-phase autotransformer that can balance phases across a neutral in a three phase system? They might exist, but I’m not aware of such a thing. I see references to three phase automatic load balancers when I do a Google search. I have no idea how much something like that would cost. Maybe you could look into it. However, I’d be willing to bet that it’s more cost effective to replace the inverters with 10kVA inverters and get on with things
I’m in Europe, not the USA, and here there are transformers for this kind of load, they’re just expensive as hell (for my setup an appropriate transformer would cost 1000€ more than buying three of the next-bigger version of Multiplus-II)
I’d like to understand the ESS’s problem with this system a bit more, in my case the generator would be “grid” and if it’s not running the Multiplus-II is the grid. I just want it so the generator runs to charge the batteries
Yes, I know you are. But the difference in voltage and frequency between the USA and Europe is irrelevant to the underlying issue. Either buy an expensive balancing system, manually balance your single-phase loads, or increase your generation capacity to accommodate unbalanced loads. That’s all I was trying to say.
ESS doesn’t really do anything magical to balance loads across a three phase system. If you have one or two phases that are unbalanced, ESS will feed in to the grid any excess capacity from one or two inverters and pull extra power from the grid for the more heavily loaded phases. Since most (all?) three phase utility metering is based on net energy and demand usage across all three phases, the “balancing” that occurs with ESS is just trying to net the inflow and outflow to try and reduce overall energy consumption from the grid.
You can’t do that with a generator. It might be technically possible but certainly not practical for your situation.
Use another inverter/charger one on each phase set up to straight up charge at a set input limit.
The generator will be evenly loaded. The batteries wont deplete. Inverters do not care about unbalanced phases within their invert ability.
Have you ever looked at the hybrid generator solution as a possible option? It is specifically designed for offgrid use with generators and can peak shave.
You have to find a way to load the phases more evenly.
All bigger loads should be 3-phase or to talk to the people using the system that they are trying to use the sockets evenly.
Maybe mark each socket with L1, L2 and L3.
ich habe leider nur eine Idee und keine Erfahrung…
Der Node Red output Node " ESS Control" hat für jede Phase einen " AC Power … setpoint". AC Power L1 setpoint (W) , dbus path: /Hub4/L1/AcPowerSetpoint , type integer
Das Gleiche schein über VEBus System aufrufbar zu sein.
Ich weiß leider nicht, wo der “Power setpoint” bei einem OffGrid-System mit Generator gemessen wird. Bei normalen ESS wird das GridMeter genommen, was bei Deinem System fehlt.
Wahrscheinlich wird Node Red nicht so schnell reagieren, wie eine native Funktion wie Power Assist. Aber vielleicht funktionert es ja…
Danke für die Idee! Ich habe einen Smart Meter am AC Ausgang, und habe schon überlegt, ob ich über Node Red einen “dynamic AC input limit”-Flow implementieren kann.
Greetings from Africa. We have similar problems on lodges in Botswana and as others have already suggested you really need to deal with the problem in the distribution. Do you not have the position/responsibility to apply more stringed regulation, like:
colour code/mark outlets with corresponding marking on the sockets to try and get users to use the phases evenly.
set the mcb’s to trip if more than an allowed number of users connect to one phase.You will be unpopular but they will learn.
install a phase load warning in each container that warns loudly of inbalances.
Load in balances do affect the inverter system in that they reduce efficiency, waste generator fuel & reduced capacity so it’s worth dealing with.
